Ring Enlargement and Sulfur-Transfer Processes in SiO2-Catalyzed Reactions of Thiocarbonyl Compounds with Optically Active Oxiranes

✍ Scribed by Sergej Malaschichin; Changchun Fu; Anthony Linden; Heinz Heimgartner

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 129 KB
• Volume: 88
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200590261

✦ Synopsis

Abstract

The reactions of 1,3‐dioxolane‐2‐thione (3) with (S)‐2‐methyloxirane ((S)‐1) and with (R)‐2‐phenyloxirane ((R)‐2) in the presence of SiO~2~ in anhydrous dichloroalkanes led to the optically active spirocyclic 1,3‐oxathiolanes 8 with Me at C(7) and 9 with Ph at C(8), respectively (Schemes 2 and 3). The analogous reaction of 1,3‐dimethylimidazolidine‐2‐thione (4a) with (R)‐2 yielded stereoselectively (S)‐2‐phenylthiirane ((S)‐10) in 83% yield and 97% ee together with 1,3‐dimethylimidazolidin‐2‐one (11a). In the cases of 3‐phenyloxazolidine‐2‐thione (4b) and 3‐phenylthiazolidine‐2‐thione (4c), the reaction with (RS)‐2 yielded the racemic thiirane (RS)‐10, and the corresponding carbonyl compounds 11b and 11c (Scheme 4 and Table 1). The analogous reaction of 4a with 1,2‐epoxycyclohexane (= 7‐oxabicyclo[4.1.0]heptane; 7) afforded thiirane 12 and the corresponding carbonyl compound 11a (Scheme 5). On the other hand, the BF~3~‐catalyzed reaction of imidazolidine‐2‐thione (5) with (RS)‐2 yielded the imidazolidine‐2‐thione derivative 13 almost quantitatively (Scheme 6). In a refluxing xylene solution, 1,3‐diacetylimidazolidine‐2‐thione (6) and (RS)‐2 reacted to give two imidazolidine‐2‐thione derivatives, 13 and 14 (Scheme 7). The structures of 13 and 14 were established by X‐ray crystallography (Fig.).