STEREOSELECTIVITY IN ELECTROPHILE-MEDIATED CYCLIZATIONS - AG(I)-CATALYZED SYNTHESIS OF DISUBSTITUTED PYRROLIDINES - CRYSTAL-STRUCTURE OF CIS-5-PHENYL-N-TOSYLPYRROLIDIN-2-YLMETHYL 4-BROMOBENZOATE

A series of phenyl-substituted allenic sulphonamides 5, 6 and 7 have been prepared and shown to undergo Ag1-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 ring-forming step play a key role in controlling the cis/trans selectivity observed in cyclisations involving 5 (cis-selective) and 7 (trans-selective). Ag1-Catalysed cyclisation of 6 to give the 2,4-disubstituted pyrrolidine 9 was, however, nonselective.