High Nucleophilicity of Cyclic Amidocarbene toward Aryl Isocyanates, New Approach to Spiro[azetidinone-4,3‘-indolinone] Derivatives

The nucleophilic addition of β-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 spiro[β-lactam-4,2‘-oxadiazolines] 1 in the presence of aryl isocyanates afforded both N-lactam and
O-lactam substituted spiro[azetidine-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 spiro[azetidine-2-one-4,3‘-indole-2‘-one] 9 that was analogous to known biologically active compounds.