Stereoselectivity in electrophile-mediated cyclisations. AgI-Catalysed synthesis of disubstituted pyrrolidines; crystal structure of cis-5-phenyl-N-tosylpyrrolidin-2-ylmethyl 4-bromobenzoate

Abstract

A series of phenyl-substituted allenic sulphonamides 5, 6 and 7 have been prepared and shown to ndergo Ag^I-catalysed cyclisation to give the corresponding 2,5-, 2,4- and 2,3-disubstituted N-sulphonylpyrrolidines 8, 9, and 10 respectively. The interactions between substituents in the ringforming step play a key role in controlling the cis/trans selectivity observed in cyclisations involving 5(cis-selective) and 7(trans-selective). Ag^I-Catalysed cyclisation of 6 to give the 2,4-disubstituted pyrrolidine 9 was, however, nonselective.