An improved, easy and efficient method for the generation of nitrile oxides from nitronates for in situ 1,3-dipolar cycloaddition

Abstract

The Michael addition of the diethyl allyl malonate anion to β-nitrostyrenes 1 generated nitronates 5. Nitronates 5 could be converted into nitrile oxides 7 to undergo intramolecular nitrile oxide–olefin cycloaddition (INOC) to form medium to high yields (51–95%) of five-membered carbocycles 8 and 9 by using ethyl chloroformate in the presence of a catalytic amount of 4-dimethylaminopyridine (DMAP). High yields (91%) of tricyclic compounds 11 and 12 were obtained when 1a reacted with the anion of 10 under similar experimental conditions and procedures.