SUBSTITUENT EFFECTS ON 1,3-DIPOLAR CYCLOADDITIONS TO SOME 1,1-DIPHENYL-2-AZA-1,3-BUTADIENE DERIVATIVES

The reactivity and in particular the siteselectivity of [3+2] electroc yclic additions to 1,1-diphenyl-2-aza-1,3-butadienes, substituted or n ot on the terminal carbon with methyl and phenyl, and with a 3-carbome thoxyl group, have been investigated with the 1,3-dipolar reagents 4-n itrobenzonitrile oxide and diazomethane. The role of the 3-carbomethox y substituent in determining the siteselectivity observed in these rea ctions is discussed in relation to experimental results and to conform ational models of some of the tested 2-azadiene dipolarophiles calcula ted on AM1 bases.