Reaction of 4‐methylene‐5(4<i>H</i>)‐oxazolones with diazomethane

Abstract

Abstract The reaction of diazomethane with some ( E ) and ( Z )‐2‐substituted‐4‐methylene‐5(4)‐oxazolones ( 1a‐c ) under two different conditions, has been studied. ( E ) and ( Z )‐1,2‐disubstituted‐7‐oxo‐6‐oxa‐4‐azaspiro[2.4]‐hept‐4‐enes ( 3a‐c, 4a‐c ) were mainly obtained, together with multiple addition compounds. The reaction showed to be stereoselective only when the substituents were aromatic. Acid hydrolysis of compounds 3a and 4a produced a mixture of ( E ) and ( Z )‐3,5‐disubstituted‐tetrahydrofuran‐2‐ones ( 8a, 9a ). Smooth methanolysis of the ring led to ( E ) and ( Z )‐1‐benzamido‐cyclopropanecarboxylic esters ( 10a‐c, 11a‐c ), which, on acid hydrolysis, gave ( E ) and ( Z )‐1‐amino‐2‐phenylcyclopropanecarboxylic acids 12a and 13a . The pmr spectra have been analyzed by an iterative computer method, and the computed best values obtained have been used to deduce the stereochemistry of the spiroderivatives.