Synthesis of 1,3-diaryl-spiro[azetidine-2,3'-indoline]-2',4-diones via the Staudinger reaction: cis - or trans -diastereoselectivity with different addition modes.

A new synthetic approach for realizing biologically relevant bis-aryl spiro[azetidine-2,3'-indoline]-2',4-diones was developed based on Staudinger ketene-imine cycloaddition through the one-pot reaction of substituted acetic acids and Schiff bases in the presence of oxalyl chloride and an organic base. A series of [azetidine-2,3'-indoline]-2',4-diones were synthesized using this method. For comparison, the same compounds were obtained using a known technique, where ketene is generated from pre-synthesized acyl chloride. It was shown that the use of oxalyl chloride for ketene generation in the one-pot reaction at room temperature allows for the reversal of the diastereoselectivity of spiro-lactam formation, unlike previously described procedures.