H IV, mp 148.5-149" 111, rnp 170' (MeO)?P(O) 'C=NN=PPhJ Ph' mp 126.5-127.5' dec tions of 11. The products of 1,3-dipolar addition of I and I1 to activated vinyl compounds appear to be 2-pyrazolines as shown; where two modes of addition are possible, the isomer involving Michael addition of the diazo carbon is favored. All 1,3-dipolar adducts showed strong NH infrared absorption at -3200 cm-l and a broad downfield singlet in the nmr spectrum, which was assignable to ...