Δ2-Isoxazoline derivatives. Part 11. Reactions of nitrile oxides, diazoalkanes, and dienes with 2-oxa-3-azabicyclo[3.2.0]hepta-3,6-diene derivatives

Abstract

Nitrile oxides and diazoalkanes with 4-phenyl-2-oxa-3-azabicyclo[3.2.0]hepta-3,6-diene yield new heterocyclic cyclobutane derivatives. The structures and stereochemistry of the cycloadducts are attributed on the basis of n.m.r., i.r., Raman, and dipole moment measurements. In all the reactions explored, the sterically favoured anti-adducts are formed in larger amounts than the syn-isomers. The observed regioisomer ratios agree with those predicted by perturbation theory. 4-Phenyl-2-oxa-3-azabicyclo[3.2.0]hepta-3,6-diene reacts as a dienophile with several dienes to give only anti-adducts.