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Kin-ya Akiba - One of the best experts on this subject based on the ideXlab platform.
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stereospecific pseudorotation of diastereomeric anti apicophilic spiroPhosphoranes a novel stereochemical transformation involving 10 p 5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Stereospecific Pseudorotation of Diastereomeric Anti‐Apicophilic SpiroPhosphoranes: A Novel Stereochemical Transformation Involving 10‐P‐5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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experimental determination of the nn σ p o interaction energy of o equatorial c apical Phosphoranes bearing a primary amino group
Inorganic Chemistry, 2006Co-Authors: Takahiro Adachi, Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa Kajiyama, Yohsuke Yamamoto, Shigeru NagaseAbstract:The reaction of a chlorophosphorane (9-Cl) with primary amines produced anti-apicophilic spiroPhosphoranes (5, O-equatorial Phosphoranes), which violate the apicophilicity concept, having an apical carbon-equatorial oxygen configuration, along with the ordinarily expected O-apical stereoisomers (6) with the apical oxygen-equatorial carbon configuration. Although the amino group is electronegative in nature, the O-equatorial Phosphoranes were found to be stable at room temperature and could still be converted to their more stable O-apical pseudorotamers (6) when they were heated in solution. X-ray analysis implied that this remarkable stability of the O-equatorial isomers could be attributed to the orbital interaction between the lone-pair electrons of the nitrogen atom (nN) and the antibonding σ*P-O orbital in the equatorial plane. A kinetic study of the isomerization of 5 to 6 and that between diastereomeric O-apical Phosphoranes 13b-exo and 13b-endo revealed that 5b bearing an n-propylamino substituent ...
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The Ligand‐Exchange Process of P–Hapical Phosphoranes and the Thermal Formation and Pseudorotation of Anti‐Apicophilic SpiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Shiro Matsukawa, Kazumasa Kajiyama, Kin-ya AkibaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
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the ligand exchange process of p hapical Phosphoranes and the thermal formation and pseudorotation of anti apicophilic spiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa KajiyamaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
Satoshi Kojima - One of the best experts on this subject based on the ideXlab platform.
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stereospecific pseudorotation of diastereomeric anti apicophilic spiroPhosphoranes a novel stereochemical transformation involving 10 p 5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Stereospecific Pseudorotation of Diastereomeric Anti‐Apicophilic SpiroPhosphoranes: A Novel Stereochemical Transformation Involving 10‐P‐5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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experimental determination of the nn σ p o interaction energy of o equatorial c apical Phosphoranes bearing a primary amino group
Inorganic Chemistry, 2006Co-Authors: Takahiro Adachi, Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa Kajiyama, Yohsuke Yamamoto, Shigeru NagaseAbstract:The reaction of a chlorophosphorane (9-Cl) with primary amines produced anti-apicophilic spiroPhosphoranes (5, O-equatorial Phosphoranes), which violate the apicophilicity concept, having an apical carbon-equatorial oxygen configuration, along with the ordinarily expected O-apical stereoisomers (6) with the apical oxygen-equatorial carbon configuration. Although the amino group is electronegative in nature, the O-equatorial Phosphoranes were found to be stable at room temperature and could still be converted to their more stable O-apical pseudorotamers (6) when they were heated in solution. X-ray analysis implied that this remarkable stability of the O-equatorial isomers could be attributed to the orbital interaction between the lone-pair electrons of the nitrogen atom (nN) and the antibonding σ*P-O orbital in the equatorial plane. A kinetic study of the isomerization of 5 to 6 and that between diastereomeric O-apical Phosphoranes 13b-exo and 13b-endo revealed that 5b bearing an n-propylamino substituent ...
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The Ligand‐Exchange Process of P–Hapical Phosphoranes and the Thermal Formation and Pseudorotation of Anti‐Apicophilic SpiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Shiro Matsukawa, Kazumasa Kajiyama, Kin-ya AkibaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
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the ligand exchange process of p hapical Phosphoranes and the thermal formation and pseudorotation of anti apicophilic spiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa KajiyamaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
Masaaki Nakamoto - One of the best experts on this subject based on the ideXlab platform.
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stereospecific pseudorotation of diastereomeric anti apicophilic spiroPhosphoranes a novel stereochemical transformation involving 10 p 5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Stereospecific Pseudorotation of Diastereomeric Anti‐Apicophilic SpiroPhosphoranes: A Novel Stereochemical Transformation Involving 10‐P‐5 Phosphoranes
European Journal of Organic Chemistry, 2008Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya AkibaAbstract:A diastereomeric pair of monocyclic apical H-Phosphoranes (2-exo and 2-exo) has been prepared from a diastereomeric pair of bicyclic equatorial H-spiroPhosphoranes (1) with tBuLi. The thermal cyclization reaction of each diastereomeric apical H-phosphorane gave rise to different diastereomeric O-equatorial anti-apicophilic Phosphoranes (3-exo and 3-endo, respectively) as single products. On the other hand, the oxidation reaction of each of these apical H-Phosphoranes was complementary to the thermal reaction, affording the opposite diastereomeric anti-apicophilic phosphorane (3-endo and 3-exo, respectively) as a single product. The pseudorotation of each of these diastereomeric anti-apicophilic Phosphoranes (3-exo and 3-endo) gave rise to different diastereomeric O-apical Phosphoranes (4-exo and 4-endo, respectively) as single products.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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experimental determination of the nn σ p o interaction energy of o equatorial c apical Phosphoranes bearing a primary amino group
Inorganic Chemistry, 2006Co-Authors: Takahiro Adachi, Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa Kajiyama, Yohsuke Yamamoto, Shigeru NagaseAbstract:The reaction of a chlorophosphorane (9-Cl) with primary amines produced anti-apicophilic spiroPhosphoranes (5, O-equatorial Phosphoranes), which violate the apicophilicity concept, having an apical carbon-equatorial oxygen configuration, along with the ordinarily expected O-apical stereoisomers (6) with the apical oxygen-equatorial carbon configuration. Although the amino group is electronegative in nature, the O-equatorial Phosphoranes were found to be stable at room temperature and could still be converted to their more stable O-apical pseudorotamers (6) when they were heated in solution. X-ray analysis implied that this remarkable stability of the O-equatorial isomers could be attributed to the orbital interaction between the lone-pair electrons of the nitrogen atom (nN) and the antibonding σ*P-O orbital in the equatorial plane. A kinetic study of the isomerization of 5 to 6 and that between diastereomeric O-apical Phosphoranes 13b-exo and 13b-endo revealed that 5b bearing an n-propylamino substituent ...
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The Ligand‐Exchange Process of P–Hapical Phosphoranes and the Thermal Formation and Pseudorotation of Anti‐Apicophilic SpiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Shiro Matsukawa, Kazumasa Kajiyama, Kin-ya AkibaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
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the ligand exchange process of p hapical Phosphoranes and the thermal formation and pseudorotation of anti apicophilic spiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa KajiyamaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
Edgar Niecke - One of the best experts on this subject based on the ideXlab platform.
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Unusual approaches to organophosphorus compounds: The surprising reactivity of bis(methylene)Phosphoranes and related phosphoranylidene carbenoids
Organometallics, 2002Co-Authors: Thomas Baumgartner, Petra Moors, Martin Nieger, Heike Hupfer, Edgar NieckeAbstract:The reactivity of the isomeric LiX-phosphoranylidene carbenoids E-, Z-[P]=C(X)Li ( [P] = Mes*P=CTms 2 ; X = Cl, Br) as well as the synthesis and reactivity of the corresponding E-[P]=C(F)Li carbenoid was examined. The carbenoids exhibit a pronounced carbanion character, and differences in their reactivity mainly stem from the configuration of the carbenoid centers and/or the nature of the halogen substituent. Reaction of the dibromo-substituted bis(methylene)phosphorane, [P]=CBr 2 , with an excess of n-BuLi proceeded through a dilithio intermediate ([P]=CLi 2 ), which was trapped with MeI and H 2 O. Endo-methylated bis(methylene)Phosphoranes ([P]=C(Me)X) exhibit a surprising acidity that, depending on the substitution pattern, induces rearrangement and/or elimination reactions. Rearrangement reactions accompanied by the loss of LiX afford a phosphirene that was used as a ligand in a nickel complex. Fluoro-substituted bis(methylene)Phosphoranes ([P]=C(F)R) show weak interactions with an adjacent γ-silyl group, leading to configurationally stable Z-systems and exhibit carbenoid character in the case of the α-silyl-substituted bis(methylene)phosphorane.
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FERROCENYLBIS(YLENE) Phosphoranes
Journal of Organometallic Chemistry, 1997Co-Authors: Rudolf Pietschnig, Edgar Niecke, Martin Nieger, Karri AirolaAbstract:The ferrocenylbis(methylene)phosphorane Fc-P(=CTms 2 ) 2 ( 1 ) (Fc = −C 5 H 4 FeC 5 H 5 ) can be synthesized starting from ferrocenyldichlorophosphane FcPCl 2 or ferrocenyldilithiophosphane FcPLl 2 . The X-ray structure of ( 1 ) shows some unusual structural features, which indicate considerable electronic interaction of the ferrocenyl group and the σ 3 λ 5 -phosphorane unit. As a consequence of this interaction, the rotational barrier of the methylene bonds is extraordinary low. Therefore, in contrast to other bis(methylene)Phosphoranes, the endo - and exo -Tms groups are indistinguishable on the NMR time scale even at −100°C. The analogous ferrocenylbis(imino)phosphorane Fc-P(=NTms) 2 ( 9 ), can only be isolated in its dimeric form. The conditions, which are necessary for the formation of ( 9 ) from the corresponding azidophosphane Fc-P(N 3 )NTms 2 under elimination of nitrogen lead to a self addition reaction of ( 9 ). The elimination of nitrogen is facilitated by polar solvents, and electrophilic reagents.
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Bis(Pentamethylcyclopentadienyl)-Substituted Phosphanes and Phosphoranes
Phosphorus Sulfur and Silicon and The Related Elements, 1996Co-Authors: Jörg Ebels, Martin Nieger, A. Dombrowski, Hans Michael Schiffner, Edgar NieckeAbstract:Abstract The synthesis and crystal structures of a series of phosphanes and Phosphoranes will be reported
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Bis(methylen)phosphorane — Synthese, spektroskopische Untersuchungen und thermische Isomerisierungen zu λ3‐Phosphiranen
Chemische Berichte, 1992Co-Authors: Petra Becker, Heike Brombach, G. David, Martina Leuer, H.‐j. Metternich, Edgar NieckeAbstract:Bis(methylene)Phosphoranes – Synthesis, Spectroscopic Investigations and Thermal Isomerizations to λ3-Phosphiranes A great number of differently substituted bis(methylene)Phosphoranes 10 [R – P{ = C(SiMe3)2}2] are obtained by nucleophilic substitution from bis[bis(trimethylsilyl)methylene]-chlorophosphorane (8). The reactions of dichlorophosphanes 1 and methylenephosphanes 3 with lithium carbenoides 2 furnish the mixed derivatives 6 [R—P( = CR1R2)( = CR3R4)] and 7 [R—P( = C(SiMe3)2( = CR3R4)]. Among these the reaction of the sterically less hindered methylenephosphanes 3c, d [R2N—P = C(H)SiMe3, R = Et, iPr] with an excess of the lithium carbenoide 2b results in the formation of the σ4λ5-phosphiranes 11a, b {R2N – P[ = C(H)SiMe3]2}. The sterically highly demanding substituents in 10a – o render great thermal stability, while the mixed bis(methylene)Phosphoranes 6, 7 rearrange to the corresponding σ4λ5-phosphiranes 15a–o. Investigations performed between 30 and 180°C reveal that all bis(methylene)Phosphoranes, with the exception of 6c, k – m and 7e, can be isomerized. – The phosphino-substituted bis(methylene)Phosphoranes 10k, 1 show different reactivity. Light-and thermally induced cleavage of the P – P bond, and dimerization of the corresponding fragments result in the formation of 14 and the diphosphanes 13a, b. The bis(methylene)Phosphoranes 10a–o are investigated by UV and NMR spectroscopy.
Kazumasa Kajiyama - One of the best experts on this subject based on the ideXlab platform.
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experimental determination of the nn σ p o interaction energy of o equatorial c apical Phosphoranes bearing a primary amino group
Inorganic Chemistry, 2006Co-Authors: Takahiro Adachi, Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa Kajiyama, Yohsuke Yamamoto, Shigeru NagaseAbstract:The reaction of a chlorophosphorane (9-Cl) with primary amines produced anti-apicophilic spiroPhosphoranes (5, O-equatorial Phosphoranes), which violate the apicophilicity concept, having an apical carbon-equatorial oxygen configuration, along with the ordinarily expected O-apical stereoisomers (6) with the apical oxygen-equatorial carbon configuration. Although the amino group is electronegative in nature, the O-equatorial Phosphoranes were found to be stable at room temperature and could still be converted to their more stable O-apical pseudorotamers (6) when they were heated in solution. X-ray analysis implied that this remarkable stability of the O-equatorial isomers could be attributed to the orbital interaction between the lone-pair electrons of the nitrogen atom (nN) and the antibonding σ*P-O orbital in the equatorial plane. A kinetic study of the isomerization of 5 to 6 and that between diastereomeric O-apical Phosphoranes 13b-exo and 13b-endo revealed that 5b bearing an n-propylamino substituent ...
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The Ligand‐Exchange Process of P–Hapical Phosphoranes and the Thermal Formation and Pseudorotation of Anti‐Apicophilic SpiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Shiro Matsukawa, Kazumasa Kajiyama, Kin-ya AkibaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
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the ligand exchange process of p hapical Phosphoranes and the thermal formation and pseudorotation of anti apicophilic spiroPhosphoranes
European Journal of Organic Chemistry, 2006Co-Authors: Satoshi Kojima, Masaaki Nakamoto, Kin-ya Akiba, Shiro Matsukawa, Kazumasa KajiyamaAbstract:Monocyclic P-H a p i c a l Phosphoranes 10 bearing a ring-opened Martin ligand are formed upon treatment of the P-H e q u a t o r i a l spirophosphorane 7 with more than 2 equiv. of alkyllithium compounds. A ligand-exchange process of these Phosphoranes 10 involving the interconversion of the bidentate Martin ligand with the monodentate Martin ligand was found to proceed, probably through a hexacoordinate phosphorus atom. Heating of 10 in nondonating solvents furnished alkylspiroPhosphoranes 5, whereas heating of 10 in donor solvents led to the formation of anti-apicophilic Phosphoranes 6, a new class of Phosphoranes in which the less apicophilic carbon substituent occupies an apical position and the more apicophilic oxygen atom occupies an equatorial position. These Phosphoranes 6 were found to completely convert into their energetically more stable C e q u a t o r i a l , O a p i c a l stereoisomers 5 upon heating. On the basis of kinetic examinations of the cyclization process of 10, the formation of 6 can be rationalized by the enhanced nucleophilicity of the hydroxy group in the donor solvents. The isomer 5b was estimated to be more stable than 6b (R = nBu) by 12 kcalmol - 1 from kinetic studies on the pseudorotation of 6b to 5b. This is in good agreement with theoretical calculations with analogous 5a and 6a (R = Me), which estimate the difference in energy to be 14.1 kcalmol - 1 .
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Novel results obtained by freezing berry pseudorotation of Phosphoranes (10‐P‐5)
Heteroatom Chemistry, 2002Co-Authors: Kin-ya Akiba, Satoshi Kojima, Masaaki Nakamoto, Shiro Matsukawa, Kazumasa Kajiyama, Yohsuke YamamotoAbstract:By freezing Berry pseudorotation of spiroPhosphoranes with recourse to the rigidity of the Martin bidentate ligand, we successfully prepared configurationally stable enantiomeric pairs of optically active Phosphoranes, and could isolate “anti-apicophilic” C-apical O-equatorial (O-cis) Phosphoranes. The effect of σ*PO orbital of the O-cis phosphorane was investigated both experimentally and theoretically. O-cis Phosphoranes were revealed to be much more electrophilic at the phosphorus atom than O-trans isomers by experimental studies. The acidity of the α-proton of an O-cis benzylphosphorane was found to be higher than that of the corresponding O-trans isomer. By the reaction of the α-carbanion of an O-cis benzylphosphorane with PhCHO, we succeeded in the first isolation and full structural characterization of a 12-P-6 phosphate bearing an oxaphosphetane ring, the intermediate in the Wittig type reaction using a 10-P-5 phosphorane. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:390–396, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10072
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Characterization of Enantiomeric Pairs of Optically Active 10-P-5 Phosphoranes with Asymmetry Only at Phosphorus
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Satoshi Kojima, Kazumasa Kajiyama, Kin-ya AkibaAbstract:Diastereomeric Phosphoranes (o-OC(CF3)2C6H4)2P*CH2CO2-(−)-menthyl (3-RP and 3-SP) of which absolute stereochemistry was determined were treated with LiAlH4 to give (o-OC(CF3)2C6H4)2P*CH2CH2OH (4-RP and 4-SP) as the first optically active pair of enantiomeric Phosphoranes of rigid stereochemistry with asymmetry only upon the pentacoordinate phosphorus atom. The high enantiomeric purities of the alcohols were confirmed by converting them to their (+)-MTPA esters. Furthermore, when diastereomeric Phosphoranes (o-OC(CF3)2C6H4)2P*CH2NHC*HCH3Ph (10-RP and 10-SP) of which absolute stereochemistry was also determined were treated with MeLi the first optically active pair of enantiomeric P–H Phosphoranes (o-OC(CF3)2C6H4)2P*H (2-RP and 2-SP) with asymmetry only upon the pentacoordinate phosphorus atom could be obtained. The high enantiomeric purities of the P–H Phosphoranes were confirmed by converting each of them to their corresponding (−)-menthyl esters 3-RP and 3-SP.
