High nucleophilicity of cyclic amidocarbene toward aryl isocyanates, new approach to spiro[azetidinone-4,3'-indolinone] derivatives

The nucleophilic addition of beta-lactam-4-ylidenes 2, a type of ambiphilic cyclic amidocarbene, to aryl isocyanates has been studied and their application in organic synthesis has been demonstrated. Thermolysis of spirobeta-lactam-4,2'-oxadiazolines] 1 in the presence of aryl isocyanates afforded both N-lactam and O-lactam substituted spiroazetidine-2-one-4,3'-indole-2'-one] derivatives 5 and 6 in the total yield of 65-86%. Upon hydrolysis, products 5 and 6 were converted into spiroazetidine-2-one-4,3'-indole-2'-one] 9 that was analogous to known biologically active compounds.