ADDITION OF N-METHYLTRIAZOLINEDIONE TO BIADAMANTYLIDENE

The addition of N-methy ltriazolinedione (M) to biadamantylidene (A gi ves the [2 + 2) adduct P, but clearly does not proceed in one step bec ause an aminoaziridinium intermediate if) can be observed to build up during the reaction. The overall rate of P formation correlates with t he amount of I that builds up, but not with any sol,ent polarity param eter despite the fact that charge-separated intermediates are involved . NMR experiments established that the equilibrium constant for I form ation is >1000 M-1 in CDCl3 greater than or equal to 500 M-1 in CD2Cl2 and in the range ca 2-15 M-1 for C6D6 and CP6Br5. It is very unlikely that I is directly on the reaction pathway between M+A and P, and it is proposed that the zwitterionic intermediate with one CN bond, X, Is the probable precursor of both I and P, although X does not build up in concentration enough to be observed CH hydrogen bonding stabilizing both X and I in chloroform is suggested as a possible rationalization for the correlation beta een overall rate of P formation and stabilit y of I relative to the starting materials. Formation of P in benzene i s catalyzed by Meldrum's acid. M unfortunately reacts too rapidly with compounds containing OH bonds to study formation of P in the presence of strong hydrogen bonding reagents. (C) 1997 by John Wiley & Sons, L td.