Stereochemical Course of the Reaction between Thiocarbonyl Compounds and Oxiranes: Reaction withcis- andtrans-2,3-Dimethyloxirane

The reactions of 4,4'‐dimethoxythiobenzophenone (1), 9H‐xanthene‐9‐thione (2), and adamantane‐2‐thione (3) with (R)‐2‐vinyloxirane [(R)‐6] in the presence of SiO2 in anhydrous CH2Cl2 at 0 °C or room temperature afforded the corresponding 4‐vinyl‐1,3‐oxathiolane derivatives (S)‐7, (S)‐9, and (S)‐11, respectively. The analogous BF3‐catalyzed reactions of (R)‐6 with 1,1,3,3‐tetramethylindane‐2‐thione (4) and 2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (5) in anhydrous CH2Cl2 at –65 °C or –78 °C yielded the corresponding spirocyclic 1,3‐oxathiolanes (S)‐12 and (S)‐14, respectively. The structures of (S)‐9 and (S)‐12 were established by X‐ray crystallography. In all cases, the nucleophilic thiocarbonyl S atom attacked predominantly C(2) of the Lewis acid‐activated (R)‐2‐vinyloxirane ring with inversion of the configuration through an SN2‐type mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Regio‐ and Stereoselectivity of the SiO₂‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes

Linden

Heimgartner

2003

Helvetica Chimica Acta

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The reactions of the enolizable thioketone (1R,4R)-thiocamphor ( (1R,4R)-1,7,7-trimethylbicyclo[2.2.1]-heptane-2-thione; 1) with (S)-2-methyloxirane (2) in the presence of a Lewis acid such as SnCl 4 or SiO 2 in anhydrous CH 2 Cl 2 led to two diastereoisomeric spirocyclic 1,3-oxathiolanes 3 and 4 with the Me group at C(5'), as well as the isomeric b-hydroxy thioether 5 (Scheme 2). The analogous reactions of 1 with (RS)-, (R)-, and (S)-2-phenyloxirane (7) yielded two isomeric spirocyclic 1,3-oxathiolanes 8 and 9 with Ph at C(4'), an additional isomer 13 bearing the Ph group at C(5'), and three isomeric b-hydroxy thioethers 10, 11, and 12 (Scheme 4). In the presence of HCl, the b-hydroxy thioethers 5, 10, 11, and 12 isomerized to the corresponding 1,3-oxathiolanes 3 and 4 (Scheme 3), and 8, 9, and 13, respectively (Scheme 5). Under similar conditions, an epimerization of 3, 8, and 9 occurred to yield the corresponding diastereoisomers 4, 14, and 15, respectively (Schemes 3 and 6). The structures of 9 and 15 were confirmed by X-ray crystallography ( Figs. 1 and 2). These results show that the Lewis acid-catalyzed addition of oxiranes to enolizable thioketones proceeds with high regio-and stereoselectivity via an S n 2-type mechanism.

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Stereochemical Course of the Reaction between Thiocarbonyl Compounds and Oxiranes: Reaction withcis- andtrans-2,3-Dimethyloxirane

Cited by 16 publications

References 19 publications

2,2,4,4-Tetramethylcyclobutane-1-one-3-thione

2,2,4,4-Tetramethylcyclobutane-1-one-3-thione

Reaction of Thioketones with (R)‐2‐Vinyloxirane: Regio‐ and Stereoselective Formation of (S)‐4‐Vinyl‐1,3‐oxathiolanes

Regio‐ and Stereoselectivity of the SiO₂‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes

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Stereochemical Course of the Reaction between Thiocarbonyl Compounds and Oxiranes: Reaction withcis- andtrans-2,3-Dimethyloxirane

Cited by 16 publications

References 19 publications

2,2,4,4-Tetramethylcyclobutane-1-one-3-thione

2,2,4,4-Tetramethylcyclobutane-1-one-3-thione

Reaction of Thioketones with (R)‐2‐Vinyloxirane: Regio‐ and Stereoselective Formation of (S)‐4‐Vinyl‐1,3‐oxathiolanes

Regio‐ and Stereoselectivity of the SiO2‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes

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Regio‐ and Stereoselectivity of the SiO₂‐Catalyzed Reaction of Thiocamphor (=1,7,7‐Trimethylbicyclo[2.2.1]heptane‐2‐thione) with Optically Active Monosubstituted Oxiranes