The Experts below are selected from a list of 2157 Experts worldwide ranked by ideXlab platform
Fumie Sato - One of the best experts on this subject based on the ideXlab platform.
-
optically active trans 4 tert butyldimethylsiloxymethyl 5 tert butyldimethylsiloxy 2 Cyclohexenone as a useful chiral building block for preparation of substituted cyclohexane rings synthesis and its highly stereoselective reaction with rcu cn li
Tetrahedron Letters, 2000Co-Authors: Takeshi Hanazawa, Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Optically active trans-4-(tert-butyldimethylsiloxymethyl)-5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (2) has been synthesized in 25% overall yield starting from easily available 1,4-bis(benzyloxy)-2,3-epoxy butane (3). The enone 2 reacts with excellent stereoselectivity with RCu(CN)Li thus working as an efficient chiral building block for preparation of substituted cyclohexane compounds.
-
asymmetric synthesis of 1α 25 dihydroxyvitamin d3 a ring precursor starting with 5 tert butyldimethylsiloxy 2 Cyclohexenone
Tetrahedron Letters, 2000Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Abstract The A-ring precursor of 1α,25-dihydroxyvitamin D3 [(E)-4] has been prepared starting from the (5S)-tert-butyldimethylsiloxy-2-Cyclohexenone [(S)-1] via eight steps in 19% overall yield, where a catalytic osmium dihydroxylation which sets the stereochemistry of the hydroxyl group at C1 and a regioselective protection of the hydroxy group as a TBS-ether are the key steps.
-
Asymmetric synthesis of palitantin from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone
Tetrahedron Letters, 1999Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Takeshi Hanazawa, Fumie SatoAbstract:Abstract (+)-Palitantin (2) has been synthesized in 25% overall yield from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone [(R)-1] where a remarkable diastereoselective cat. OsO4 cis-dihydroxylation of (R)-1 furnished the precursor of the optically pure (5R,6R)-bis-trimethylsiloxy 2-Cyclohexenone (7) which underwent highly selectively the 1,4-addition reaction of the 1,3-heptadienyl cyanocuprate to give, after trapping of the corresponding copper enolate with formaldehyde, the target compound.
-
synthesis of optically active 5 tert butyldimethylsiloxy 2 Cyclohexenone and its 6 substituted derivatives as useful chiral building blocks for the synthesis of cyclohexane rings syntheses of carvone penienone and penihydrone
Journal of the American Chemical Society, 1999Co-Authors: Georges P.‐j. Hareau, Shinichi Hikichi, Masakazu Koiwa, Fumie SatoAbstract:Optically active 5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (1) and its 6-substituted derivatives 2a,b were synthesized from the readily available optically active ethyl 3-(tert-butyldimethylsiloxy)-5-hexenoate (4), where the Ti(II)-mediated intramolecular nucleophilic acyl substitution reaction and the FeCl3-mediated ring expansion reaction of a 1-hydroxybicyclo[3.1.0]hexane are the key reactions. The enone 1 reacted with higher-order cyanocuprates with excellent diastereoselectivity to afford the trans-addition products, trans-13, in excellent yields. The reaction of 1 with lower-order cyanocuprates proceeded with moderate to excellent syn-selectivity to afford cis-13. Treatment of trans- and cis-13 with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or catalyst p-TSA (p-toluenesulfonic acid) resulted in a β-elimination reaction to furnish the corresponding optically active 5-substituted-2-Cyclohexenones 14. The 1,4-addition reaction of 2a and 2b with organocyanocuprates followed by treatment of the resulti...
-
unexpected cis selective 1 4 addition reaction of lower order cyanocuprates to optically active 5 tert butyldimethylsiloxy 2 Cyclohexenone
Angewandte Chemie, 1998Co-Authors: Georges Hareauvittini, Shinichi Hikichi, Fumie SatoAbstract:: A remarkable cis selectivity has been observed in the 1,4-addition of lower order primary and secondary alkylcyanocuprates to 5-silyloxy- and 5-benzyloxy-substituted Cyclohexenones. This enables the preparation of both enantiomers of the corresponding 5-alkyl-substituted Cyclohexenones (S)- and (R)-3 by the reaction of the readily available 5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (1) with either the lower or higher order cyanocuprate. DBU=1,8-diazabicyclo[5.4.0]undec-7-ene.
Georges P.‐j. Hareau - One of the best experts on this subject based on the ideXlab platform.
-
optically active trans 4 tert butyldimethylsiloxymethyl 5 tert butyldimethylsiloxy 2 Cyclohexenone as a useful chiral building block for preparation of substituted cyclohexane rings synthesis and its highly stereoselective reaction with rcu cn li
Tetrahedron Letters, 2000Co-Authors: Takeshi Hanazawa, Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Optically active trans-4-(tert-butyldimethylsiloxymethyl)-5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (2) has been synthesized in 25% overall yield starting from easily available 1,4-bis(benzyloxy)-2,3-epoxy butane (3). The enone 2 reacts with excellent stereoselectivity with RCu(CN)Li thus working as an efficient chiral building block for preparation of substituted cyclohexane compounds.
-
asymmetric synthesis of 1α 25 dihydroxyvitamin d3 a ring precursor starting with 5 tert butyldimethylsiloxy 2 Cyclohexenone
Tetrahedron Letters, 2000Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Abstract The A-ring precursor of 1α,25-dihydroxyvitamin D3 [(E)-4] has been prepared starting from the (5S)-tert-butyldimethylsiloxy-2-Cyclohexenone [(S)-1] via eight steps in 19% overall yield, where a catalytic osmium dihydroxylation which sets the stereochemistry of the hydroxyl group at C1 and a regioselective protection of the hydroxy group as a TBS-ether are the key steps.
-
Asymmetric synthesis of palitantin from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone
Tetrahedron Letters, 1999Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Takeshi Hanazawa, Fumie SatoAbstract:Abstract (+)-Palitantin (2) has been synthesized in 25% overall yield from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone [(R)-1] where a remarkable diastereoselective cat. OsO4 cis-dihydroxylation of (R)-1 furnished the precursor of the optically pure (5R,6R)-bis-trimethylsiloxy 2-Cyclohexenone (7) which underwent highly selectively the 1,4-addition reaction of the 1,3-heptadienyl cyanocuprate to give, after trapping of the corresponding copper enolate with formaldehyde, the target compound.
-
synthesis of optically active 5 tert butyldimethylsiloxy 2 Cyclohexenone and its 6 substituted derivatives as useful chiral building blocks for the synthesis of cyclohexane rings syntheses of carvone penienone and penihydrone
Journal of the American Chemical Society, 1999Co-Authors: Georges P.‐j. Hareau, Shinichi Hikichi, Masakazu Koiwa, Fumie SatoAbstract:Optically active 5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (1) and its 6-substituted derivatives 2a,b were synthesized from the readily available optically active ethyl 3-(tert-butyldimethylsiloxy)-5-hexenoate (4), where the Ti(II)-mediated intramolecular nucleophilic acyl substitution reaction and the FeCl3-mediated ring expansion reaction of a 1-hydroxybicyclo[3.1.0]hexane are the key reactions. The enone 1 reacted with higher-order cyanocuprates with excellent diastereoselectivity to afford the trans-addition products, trans-13, in excellent yields. The reaction of 1 with lower-order cyanocuprates proceeded with moderate to excellent syn-selectivity to afford cis-13. Treatment of trans- and cis-13 with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or catalyst p-TSA (p-toluenesulfonic acid) resulted in a β-elimination reaction to furnish the corresponding optically active 5-substituted-2-Cyclohexenones 14. The 1,4-addition reaction of 2a and 2b with organocyanocuprates followed by treatment of the resulti...
-
efficient and practical synthesis of optically active 5 t butyldimethylsiloxy 2 Cyclohexenone as a convenient chiral 2 5 cyclohexadienone synthon
Tetrahedron Letters, 1997Co-Authors: Shinichi Hikichi, Georges P.‐j. Hareau, Fumie SatoAbstract:An efficient and practical method for the preparation of optically active 5-t-butyldimethylsiloxy-2-Cyclohexenone (3), a convenient chiral 2,5-cyclohexadienone synthon, from readily available ethyl 4-chloro-3-hydroxy-butyrate (7) has been developed where Ti(II)-mediated intramolecular nucleophilic acyl substitution and FeCl3-mediated ring expansion are the key reactions. The synthesis of racemic 6-t-butyldimethylsiloxy-2-cycloheptenone (10), a potential 2,6-cycloheptadienone synthon, is also described.
Carmen Claver - One of the best experts on this subject based on the ideXlab platform.
-
thioether phosphinite and diphosphinite ligands derived from d xylose for the copper catalyzed asymmetric 1 4 addition to 2 Cyclohexenone
Tetrahedron-asymmetry, 2005Co-Authors: Eugeni Guimet, Montserrat Dieguez, Aurora Ruiz, Carmen ClaverAbstract:Abstract A series of thioether–phosphinite 1–3 and diphosphinite 4 and 5 ligands, derived from inexpensive d -(+)-xylose, were tested for the first time in the Cu-catalyzed asymmetric 1,4-addition to 2-Cyclohexenone 6. Good enantioselectivities (up to 72%) and activities [TOF up to >1225 mol (mol h−1)] combined with excellent selectivity in the 1,4 product were obtained. Our results show that activity and selectivity (chemo- and enantioselectivity) depend strongly on the type of functional group at the C-5 position of the carbohydrate backbone, the steric properties of the substituent in the thioether moiety, the catalyst precursor and the alkylating agent.
-
Thioether–phosphinite and diphosphinite ligands derived from d-xylose for the copper-catalyzed asymmetric 1,4-addition to 2-Cyclohexenone
Tetrahedron: Asymmetry, 2005Co-Authors: Eugeni Guimet, Montserrat Dieguez, Aurora Ruiz, Carmen ClaverAbstract:Abstract A series of thioether–phosphinite 1–3 and diphosphinite 4 and 5 ligands, derived from inexpensive d -(+)-xylose, were tested for the first time in the Cu-catalyzed asymmetric 1,4-addition to 2-Cyclohexenone 6. Good enantioselectivities (up to 72%) and activities [TOF up to >1225 mol (mol h−1)] combined with excellent selectivity in the 1,4 product were obtained. Our results show that activity and selectivity (chemo- and enantioselectivity) depend strongly on the type of functional group at the C-5 position of the carbohydrate backbone, the steric properties of the substituent in the thioether moiety, the catalyst precursor and the alkylating agent.
-
copper catalysed asymmetric 1 4 addition of organometallic reagents to 2 Cyclohexenone using novel phosphine phosphite ligands
Tetrahedron-asymmetry, 2000Co-Authors: Montserrat Dieguez, Sirik Deerenberg, Oscar Pamies, Carmen Claver, P W N M Van Leeuwen, Paul C J KamerAbstract:Abstract A series of novel non-symmetrical phosphine-phosphite ligands 1 – 10 have been tested in the copper-catalysed asymmetric addition of diethylzinc and triethylaluminium to 2-Cyclohexenone. In all cases, excellent conversion and regioselectivities for the 1,4-product were found. Good enantiomeric excesses (up to 62%) were obtained when triethylaluminium was used as the alkylating reagent.
Masakazu Koiwa - One of the best experts on this subject based on the ideXlab platform.
-
optically active trans 4 tert butyldimethylsiloxymethyl 5 tert butyldimethylsiloxy 2 Cyclohexenone as a useful chiral building block for preparation of substituted cyclohexane rings synthesis and its highly stereoselective reaction with rcu cn li
Tetrahedron Letters, 2000Co-Authors: Takeshi Hanazawa, Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Optically active trans-4-(tert-butyldimethylsiloxymethyl)-5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (2) has been synthesized in 25% overall yield starting from easily available 1,4-bis(benzyloxy)-2,3-epoxy butane (3). The enone 2 reacts with excellent stereoselectivity with RCu(CN)Li thus working as an efficient chiral building block for preparation of substituted cyclohexane compounds.
-
asymmetric synthesis of 1α 25 dihydroxyvitamin d3 a ring precursor starting with 5 tert butyldimethylsiloxy 2 Cyclohexenone
Tetrahedron Letters, 2000Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Fumie SatoAbstract:Abstract The A-ring precursor of 1α,25-dihydroxyvitamin D3 [(E)-4] has been prepared starting from the (5S)-tert-butyldimethylsiloxy-2-Cyclohexenone [(S)-1] via eight steps in 19% overall yield, where a catalytic osmium dihydroxylation which sets the stereochemistry of the hydroxyl group at C1 and a regioselective protection of the hydroxy group as a TBS-ether are the key steps.
-
Asymmetric synthesis of palitantin from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone
Tetrahedron Letters, 1999Co-Authors: Georges P.‐j. Hareau, Masakazu Koiwa, Takeshi Hanazawa, Fumie SatoAbstract:Abstract (+)-Palitantin (2) has been synthesized in 25% overall yield from the (5R)-tert-butyldimethylsiloxy-2-Cyclohexenone [(R)-1] where a remarkable diastereoselective cat. OsO4 cis-dihydroxylation of (R)-1 furnished the precursor of the optically pure (5R,6R)-bis-trimethylsiloxy 2-Cyclohexenone (7) which underwent highly selectively the 1,4-addition reaction of the 1,3-heptadienyl cyanocuprate to give, after trapping of the corresponding copper enolate with formaldehyde, the target compound.
-
synthesis of optically active 5 tert butyldimethylsiloxy 2 Cyclohexenone and its 6 substituted derivatives as useful chiral building blocks for the synthesis of cyclohexane rings syntheses of carvone penienone and penihydrone
Journal of the American Chemical Society, 1999Co-Authors: Georges P.‐j. Hareau, Shinichi Hikichi, Masakazu Koiwa, Fumie SatoAbstract:Optically active 5-(tert-butyldimethylsiloxy)-2-Cyclohexenone (1) and its 6-substituted derivatives 2a,b were synthesized from the readily available optically active ethyl 3-(tert-butyldimethylsiloxy)-5-hexenoate (4), where the Ti(II)-mediated intramolecular nucleophilic acyl substitution reaction and the FeCl3-mediated ring expansion reaction of a 1-hydroxybicyclo[3.1.0]hexane are the key reactions. The enone 1 reacted with higher-order cyanocuprates with excellent diastereoselectivity to afford the trans-addition products, trans-13, in excellent yields. The reaction of 1 with lower-order cyanocuprates proceeded with moderate to excellent syn-selectivity to afford cis-13. Treatment of trans- and cis-13 with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or catalyst p-TSA (p-toluenesulfonic acid) resulted in a β-elimination reaction to furnish the corresponding optically active 5-substituted-2-Cyclohexenones 14. The 1,4-addition reaction of 2a and 2b with organocyanocuprates followed by treatment of the resulti...
Somsak Ruchirawat - One of the best experts on this subject based on the ideXlab platform.
-
synthesis of 2 Cyclohexenone 2 carboxylate and 4 chloro 2 Cyclohexenone 2 carboxylate derivatives by cyclization of alkyne tethered 1 3 ketoesters
Asian Journal of Organic Chemistry, 2018Co-Authors: Wilailak Kaewsri, Krissada Norseeda, Sureeporn Ruengsangtongkul, Nattawadee Chaisan, Charnsak Thongsornkleeb, Jumreang Tummatorn, Somsak RuchirawatAbstract:A method for the TfOH-promoted (Tf=trifluoromethanesulfonyl) cyclization of alkyne-tethered 1,3-ketoesters to afford 2-Cyclohexenone-2-carboxylate derivatives has been developed. The procedure requires no transition-metal reagent or catalyst and is practical to conduct under mild conditions. 2-Cyclohexenone-2-carboxylate derivatives were obtained in moderate to good yields without any evidence of decarboxylation. In addition, the approach can be easily adapted as a one-pot sequential cyclization/chlorination protocol that selectively provides access to 4-chloro-2-Cyclohexenone-2-carboxylate derivatives in moderate to good yields.
-
Synthesis of 2‐Cyclohexenone‐2‐carboxylate and 4‐Chloro‐2‐Cyclohexenone‐2‐carboxylate Derivatives by Cyclization of Alkyne‐Tethered 1,3‐Ketoesters
Asian Journal of Organic Chemistry, 2017Co-Authors: Wilailak Kaewsri, Krissada Norseeda, Sureeporn Ruengsangtongkul, Nattawadee Chaisan, Charnsak Thongsornkleeb, Jumreang Tummatorn, Somsak RuchirawatAbstract:A method for the TfOH-promoted (Tf=trifluoromethanesulfonyl) cyclization of alkyne-tethered 1,3-ketoesters to afford 2-Cyclohexenone-2-carboxylate derivatives has been developed. The procedure requires no transition-metal reagent or catalyst and is practical to conduct under mild conditions. 2-Cyclohexenone-2-carboxylate derivatives were obtained in moderate to good yields without any evidence of decarboxylation. In addition, the approach can be easily adapted as a one-pot sequential cyclization/chlorination protocol that selectively provides access to 4-chloro-2-Cyclohexenone-2-carboxylate derivatives in moderate to good yields.