Polar effects in the reactions of a series of substituted diazodiphenylmethanes with tetracyanoethylene in benzene

Abstract

The kinetics of the reactions of meta- and para-substituted diazodiphenylmethanes (DDM) with tetracyanoethylene (TCNE) in benzene are reported. The corresponding 1,1-diaryl-2,2,3,3-tetracyanocyclopropanes were produced almost quantitatively and the second-order rate constants k increased with the electron-donating ability of the substituents; the presence of p-OCH₃ and p′-CH₃ groups resulted in the reaction being ca. 6.5 × 10³ times faster than for the m-Cl substituent. At 30 °C, log k=–2.67 σ⁺–1.23 (r–0.989). E.s.r. measurements showed the presence of the radical anion of TCNE, though the counter radical cation derived from the diazo-compounds could not be detected. The mechanism of these reactions is discussed on the basis of initial electron transfer from the diazo-compound to TCNE.