AZA-ENAMINES-VII. UMPOLUNG OF THE AZOMETHINE REACTIVITY IN THE REACTION OF ALDEHYDE HYDRAZONES WITH SULFONYL ISOCYANATES SUBSTITUENT EFFECTS

Article abstract of DOI:10.1016/S0040-4020(01)83450-5

Sulfonyl isocyanates attack the arylaldehyde N,N-dialkylhydrazones 1-3 at the nitrogen or carbon of the azomethine function leading to the formation of the hexahydro-1,3,5-triazine-2,4-diones 4-6 or arylglyoxylic acid sulfonamide-N,N-dialkylhydrazones 7-9 (scheme 1).Under equal experimental conditions the position of the electrophilic attack depends on the contribution of the dipolar structures I'<-->I'' determined by the electron withdrawing or donating potential of the substituents R¹ and NR2.The normal reactivity of the =C=N-function is described by eq.1, the umpolung by eq.2.These different reactions correspond to the 13C-chemical shifts of the azomethine carbon atoms.