Long‐range 4J coupling constants and conformation of the four‐membered heterocycles

The correlation between the puckering angle of the four-membered cycle and 4J has been obtained from analysis of the PMR spectra of some 2-substituted azetidines and oxetanes. The absolute values of 4Jcis and 4Jtrans were found to decrease with decreasing of the puckering angle.