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Rolf Huisgen - One of the best experts on this subject based on the ideXlab platform.
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cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:Regiochemistry and methylene transfer reactions in cycloadditions of aliphatic thiocarbonyl S-methylides and Thiobenzophenone are analyzed by ab initio [(U)HF/3-21G*] and DFT calculations [(U)B3LYP/6-31G*//(U)HF/3-21G* and (U)B3LYP/6-31G*]. The formation of regioisomeric 1,3-dithiolanes is explained by the competition of concerted (2,4-substituted 1,3-dithiolane) and stepwise cycloaddition via C,C-biradicals (4,5-substituted 1,3-dithiolane). Aliphatic thiocarbonyl S-methylides with sterically demanding substituents undergo substantial methylene transfer in the reaction with Thiobenzophenone. This process involves dissociation of the C,C-biradical intermediate with liberation of Thiobenzophenone S-methylide which, in turn, combines with a second molecule of Thiobenzophenone. Calculated activation parameters for the different processes are in agreement with the experimental observations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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aliphatic thiocarbonyl ylides and Thiobenzophenone experimental study of regiochemistry and methylene transfer in cycloadditions
European Journal of Organic Chemistry, 2005Co-Authors: Rolf Huisgen, Grzegorz Mloston, Kurt Polborn, Henry Giera, Elke Langhals, Reiner SustmannAbstract:1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D – sterically hindered at least at one terminus – with Thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C-biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by ‘methylene transfer’, i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of Thiobenzophenone. The Thiobenzophenone S-alkylide 11, thus formed, rapidly reacts with a second molecule ofThiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C-biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C-biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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cover picture cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study eur j org chem 8 2005
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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Cover Picture: Cycloadditions and Methylene Transfer in Reactions of Substituted Thiocarbonyl S‐Methylides with Thiobenzophenone: A Computational Study (Eur. J. Org. Chem. 8/2005)
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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a computational study of the cycloaddition of Thiobenzophenone s methylide to Thiobenzophenone
Journal of the American Chemical Society, 2003Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cycloaddition of Thiobenzophenone S-methylide to Thiobenzophenone, an experimentally well-known reaction, was studied, using (U)HF/3-21G* for finding stationary points and (U)B3LYP/6-31G*//(U)HF/3-21G* single-point calculations for energies. Some optimizations were performed by (U)B3LYP/ 6-31G* to check the reliability of the calculations. The comparison of the concerted pathways and stepwise reactions via C,C-biradicals and C,S-zwitterions showed that the formation of a tetraphenyl-substituted C,C-biradical and its ring closure to 4,4,5,5-tetraphenyl-1,3-dithiolane constitutes the energetically most probable pathway of product formation, despite the fact that the regioisomeric 2,2,4,4-tetraphenyl-substituted product is more favorable by 17 kcal mol-1. Model calculations on bond dissociation energies showed that (U)B3LYP with various basis sets overestimates radical stabilization, whereas CBS-QB3 closely reproduced experimental values. Results with the BLYP functional are similar to those with B3LYP. ...
Reiner Sustmann - One of the best experts on this subject based on the ideXlab platform.
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cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:Regiochemistry and methylene transfer reactions in cycloadditions of aliphatic thiocarbonyl S-methylides and Thiobenzophenone are analyzed by ab initio [(U)HF/3-21G*] and DFT calculations [(U)B3LYP/6-31G*//(U)HF/3-21G* and (U)B3LYP/6-31G*]. The formation of regioisomeric 1,3-dithiolanes is explained by the competition of concerted (2,4-substituted 1,3-dithiolane) and stepwise cycloaddition via C,C-biradicals (4,5-substituted 1,3-dithiolane). Aliphatic thiocarbonyl S-methylides with sterically demanding substituents undergo substantial methylene transfer in the reaction with Thiobenzophenone. This process involves dissociation of the C,C-biradical intermediate with liberation of Thiobenzophenone S-methylide which, in turn, combines with a second molecule of Thiobenzophenone. Calculated activation parameters for the different processes are in agreement with the experimental observations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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aliphatic thiocarbonyl ylides and Thiobenzophenone experimental study of regiochemistry and methylene transfer in cycloadditions
European Journal of Organic Chemistry, 2005Co-Authors: Rolf Huisgen, Grzegorz Mloston, Kurt Polborn, Henry Giera, Elke Langhals, Reiner SustmannAbstract:1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D – sterically hindered at least at one terminus – with Thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C-biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by ‘methylene transfer’, i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of Thiobenzophenone. The Thiobenzophenone S-alkylide 11, thus formed, rapidly reacts with a second molecule ofThiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C-biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C-biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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cover picture cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study eur j org chem 8 2005
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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Cover Picture: Cycloadditions and Methylene Transfer in Reactions of Substituted Thiocarbonyl S‐Methylides with Thiobenzophenone: A Computational Study (Eur. J. Org. Chem. 8/2005)
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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a computational study of the cycloaddition of Thiobenzophenone s methylide to Thiobenzophenone
Journal of the American Chemical Society, 2003Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cycloaddition of Thiobenzophenone S-methylide to Thiobenzophenone, an experimentally well-known reaction, was studied, using (U)HF/3-21G* for finding stationary points and (U)B3LYP/6-31G*//(U)HF/3-21G* single-point calculations for energies. Some optimizations were performed by (U)B3LYP/ 6-31G* to check the reliability of the calculations. The comparison of the concerted pathways and stepwise reactions via C,C-biradicals and C,S-zwitterions showed that the formation of a tetraphenyl-substituted C,C-biradical and its ring closure to 4,4,5,5-tetraphenyl-1,3-dithiolane constitutes the energetically most probable pathway of product formation, despite the fact that the regioisomeric 2,2,4,4-tetraphenyl-substituted product is more favorable by 17 kcal mol-1. Model calculations on bond dissociation energies showed that (U)B3LYP with various basis sets overestimates radical stabilization, whereas CBS-QB3 closely reproduced experimental values. Results with the BLYP functional are similar to those with B3LYP. ...
Grzegorz Mloston - One of the best experts on this subject based on the ideXlab platform.
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applications of Thiobenzophenone for the synthesis of 3 4 5 and 6 membered sulfur heterocycles
Chemistry of Heterocyclic Compounds, 2016Co-Authors: Grzegorz Mloston, Paulina GrzelakAbstract:The review summarizes representative applications of Thiobenzophenone for the synthesis of sulfur heterocycles with diverse ring size.
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Reactions of Selected Aromatic Thioketones with Dodecarbonyltriiron
European Journal of Inorganic Chemistry, 2010Co-Authors: Ahmad Q. Daraosheh, Grzegorz Mloston, Helmar Görls, Mohammad El-khateeb, Wolfgang WeigandAbstract:Dodecacarbonyltriiron reacts with 3,3,5,5-tetraphenyl-1,2,4-trithiolanes (1e) to give the ortho-metalated complex Fe2(CO)6[κ,μ-S,η2-(C13H10S)] (9a), complexes of the type (Ph2C)S2Fe2(CO)6 and the well known trinuclear complex Fe3S2 (CO)9 as by-products. Complex 9a can also be obtained from the reaction of Fe3(CO)12 with Thiobenzophenone (2a). In a similar way, 4,4′-bis(dimethylamino)Thiobenzophenone (2b) reacts with Fe3(CO)12 to give Fe2(CO)6[κ,μ-S,η2-(C17H20N2S)] (9b). The cyclic aromatic thioketones such as dibenzosuberenethione (2c) and xanthione (2d) react with Fe3(CO)12 to give the cyclometalated products Fe2(CO)6[κ,μ-S,η2-(C15H12S)] (9c) and Fe2(CO)6[κ,μ-S,η2-(C13H8OS)] (9d), respectively, and a small amount of Fe3S2(CO)9. Complexes 9a–d have been characterized by IR and NMR spectroscopies, elemental analyses, and X-ray single crystal structure analyses.
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1,3-Dipolar Cycloadditions of some Azomethine Ylides to Thioketones
Bulletin des Sociétés Chimiques Belges, 2010Co-Authors: Grzegorz Mloston, Zuzanna SkrzypekAbstract:Reactions of the azomethine ylides generated from cis-1-substituted-2,3-diphenylaziridines 1a-b or from 1,2,3-triazoline 5 with Thiobenzophenone, adamantanethione and 2,2,4,4-tetramethyl-3-thioxocyclobutanone are described.
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aliphatic thiocarbonyl ylides and Thiobenzophenone experimental study of regiochemistry and methylene transfer in cycloadditions
European Journal of Organic Chemistry, 2005Co-Authors: Rolf Huisgen, Grzegorz Mloston, Kurt Polborn, Henry Giera, Elke Langhals, Reiner SustmannAbstract:1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D – sterically hindered at least at one terminus – with Thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C-biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by ‘methylene transfer’, i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of Thiobenzophenone. The Thiobenzophenone S-alkylide 11, thus formed, rapidly reacts with a second molecule ofThiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C-biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C-biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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Episulfidation of trans‐Cyclooctene with an 1,2,4‐Oxadithiolane
European Journal of Organic Chemistry, 2003Co-Authors: Waldemar Adam, Rainer M. Bargon, Grzegorz MlostonAbstract:The dipolar cycloaddition of Thiobenzophenone S-oxide (1) and 2,2,4,4-tetramethyl-3-thioxocyclobutanone (2) generates the labile 1,2,4-oxadithiolane I, which in the presence of trans-cyclooctene (3) affords trans-episulfide (9). In this direct sulfur transfer, the oxathiirane II and/or the dithiirane IV, both derived from the 1,2,4-oxadithiolane I, are proposed as elusive episulfidating agents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Kentaro Okuma - One of the best experts on this subject based on the ideXlab platform.
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Unusual formation of a thiacyclopent‐2‐ene by the reaction of 4,4′‐dimethoxyThiobenzophenone with tetracyanoethylene
Heteroatom Chemistry, 2020Co-Authors: Kentaro Okuma, Yoshikazu TsujimotoAbstract:The reaction of 4,4′-dimethoxyThiobenzophenone (1a) with tetracyanoethylene (TCNE) afforded an unusual type of 2:1 adduct with the structure of thiacyclopent-2-ene (5a). On the other hand, the reaction of Thiobenzophenone (1b) with TCNE afforded the corresponding thiophene, the normal 2:1 adduct (2b). The mechanism of the formation of 5a is discussed. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:259–262, 2001
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unusual formation of a thiacyclopent 2 ene by the reaction of 4 4 dimethoxyThiobenzophenone with tetracyanoethylene
Heteroatom Chemistry, 2001Co-Authors: Kentaro Okuma, Yoshikazu TsujimotoAbstract:The reaction of 4,4′-dimethoxyThiobenzophenone (1a) with tetracyanoethylene (TCNE) afforded an unusual type of 2:1 adduct with the structure of thiacyclopent-2-ene (5a). On the other hand, the reaction of Thiobenzophenone (1b) with TCNE afforded the corresponding thiophene, the normal 2:1 adduct (2b). The mechanism of the formation of 5a is discussed. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:259–262, 2001
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reaction of electronically stabilized thiones with benzyne the isolation of Thiobenzophenone benzyne and thiopivalophenone benzyne adducts
Bulletin of the Chemical Society of Japan, 2000Co-Authors: Kentaro Okuma, Tsugio Kitamura, Yuzo Fujiwara, Kyoko Shiki, Shinya Sonoda, Yuji Koga, Kosei Shioji, Yoshinobu YokomoriAbstract:The reaction of Thiobenzophenones (1) with phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate (4) in the presence of tetrabutylammonium fluoride afforded the corresponding [4+2] cycloadducts, which are the first examples of Thiobenzophenone-benzyne adducts. The reaction of thiopivalophenone (6) with benzyne prepared from 4 and tetrabutylammonium fluoride at room temperature gave [2+2] cycloadducts (7). When the reaction was carried out in refluxing dichloromethane, a mixture of 7 and [4+2] cycloadducts (13) was obtained.
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Reaction of Thiobenzophenones with Benzyne
Phosphorus Sulfur and Silicon and The Related Elements, 1997Co-Authors: Kentaro Okuma, Toshiro Yamamoto, Takafumi Shirokawa, Tsugio Kitamura, Yuzo FujiwaraAbstract:Reaction of Thiobenzophenones with phenyl[2-(trimethylsilyl)-phenyl]iodonium trifluoromethanesulfonate in the presence of tetrabutylammonium fluoride afforded the corresponding adducts, which are the first examples of benzyne-Thiobenzophenone adducts.
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the first isolation of benzyne Thiobenzophenone adducts
Tetrahedron Letters, 1996Co-Authors: Kentaro Okuma, Toshiro Yamamoto, Takafumi Shirokawa, Tsugio Kitamura, Yuzo FujiwaraAbstract:Abstract Reaction of Thiobenzophenones with phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfonate in the presence of tetrabutylammonium fluoride afforded the corresponding adducts, which are the first examples of benzync-Thiobenzophenone adducts.
Willi Sicking - One of the best experts on this subject based on the ideXlab platform.
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cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:Regiochemistry and methylene transfer reactions in cycloadditions of aliphatic thiocarbonyl S-methylides and Thiobenzophenone are analyzed by ab initio [(U)HF/3-21G*] and DFT calculations [(U)B3LYP/6-31G*//(U)HF/3-21G* and (U)B3LYP/6-31G*]. The formation of regioisomeric 1,3-dithiolanes is explained by the competition of concerted (2,4-substituted 1,3-dithiolane) and stepwise cycloaddition via C,C-biradicals (4,5-substituted 1,3-dithiolane). Aliphatic thiocarbonyl S-methylides with sterically demanding substituents undergo substantial methylene transfer in the reaction with Thiobenzophenone. This process involves dissociation of the C,C-biradical intermediate with liberation of Thiobenzophenone S-methylide which, in turn, combines with a second molecule of Thiobenzophenone. Calculated activation parameters for the different processes are in agreement with the experimental observations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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cover picture cycloadditions and methylene transfer in reactions of substituted thiocarbonyl s methylides with Thiobenzophenone a computational study eur j org chem 8 2005
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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Cover Picture: Cycloadditions and Methylene Transfer in Reactions of Substituted Thiocarbonyl S‐Methylides with Thiobenzophenone: A Computational Study (Eur. J. Org. Chem. 8/2005)
European Journal of Organic Chemistry, 2005Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cover picture shows the potential energy diagram of methylene transfer from 4,4,5,5-tetramethylcyclopentanethione S-methylide to Thiobenzophenone via a biradical intermediate which wins over a possible formation of regioisomeric cycloadducts. Methylene transfer reactions together with 1,3-dipolar cycloadditions of other thiocarbonyl S-methylides to thiones are described by R. Huisgen et al. on p. 1519 ff. DFT calculations on the mechanism of these reactions, concerted or stepwise, are reported by R. Sustmann et al. on p. 1505 ff.
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a computational study of the cycloaddition of Thiobenzophenone s methylide to Thiobenzophenone
Journal of the American Chemical Society, 2003Co-Authors: Reiner Sustmann, Willi Sicking, Rolf HuisgenAbstract:The cycloaddition of Thiobenzophenone S-methylide to Thiobenzophenone, an experimentally well-known reaction, was studied, using (U)HF/3-21G* for finding stationary points and (U)B3LYP/6-31G*//(U)HF/3-21G* single-point calculations for energies. Some optimizations were performed by (U)B3LYP/ 6-31G* to check the reliability of the calculations. The comparison of the concerted pathways and stepwise reactions via C,C-biradicals and C,S-zwitterions showed that the formation of a tetraphenyl-substituted C,C-biradical and its ring closure to 4,4,5,5-tetraphenyl-1,3-dithiolane constitutes the energetically most probable pathway of product formation, despite the fact that the regioisomeric 2,2,4,4-tetraphenyl-substituted product is more favorable by 17 kcal mol-1. Model calculations on bond dissociation energies showed that (U)B3LYP with various basis sets overestimates radical stabilization, whereas CBS-QB3 closely reproduced experimental values. Results with the BLYP functional are similar to those with B3LYP. ...
