Synthesis of 25-Disubstituted 3-(Phenylsulfonyl)pyrrolidines via 5-i Endo- Trig Cyclisation Reactions

Reaction of lithiated (phenylsulfonyl)methane with enantiomerically pure N-diphenylphosphinylaziridines gives adducts 4, which may be acylated at the sulfone a-position by further lithiation and reaction with non-enolisable acid chlorides, giving ketones 5. Reduction followed by acetylation gives substrates 6, which undergo elimination and 5-endo-trig cyclisation to give 2,5-disubstituted 3-(phenylsulfonyl)pyrrolidines 7 in high yields and with excellent stereoselectivities. Some further reactions of the pyrrolidines are described.