Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

1,3-Dipolar cycloadditions of isatins, benzylamine and benzylideneacetones were studied to prepare a series of novel spiropyrrolidine-oxindoles - 4'-acetyl-3',5'-diarylspiro[indoline-3,2'-pyrrolidin]-2-ones and 3'-acetyl-4',5'-diarylspiro[indoline-3,2'-pyrrolidine]-2-ones in good yields of up to 94% and with good regioselectivities. Regioselectivities are reversible by the addition of water or 4-nitrobenzoic acid, respectively. The substituent effects on the regioselectivity were also investigated.