The dimroth rearrangement. Part VIII. Rate enhancement by electron-withdrawal in simple iminopyrimidines

Abstract

The rates of rearrangement of 1-alkyl-1,2-dihydro-2-iminopyrimidines to 2-alkylaminopyrimidines are increased by 5-cyano-, 5-carbamoyl-, or 5-halo-substituents, and also by replacement of the alkyl group with an allyl, β-hydroxyethyl-, benzyl-, or p-nitrobenzyl-substituent. 5-Cyano-1,2-dihydro-2-imino-1,4,6-trimethylpyrimidine, unlike its 1-monomethyl homologue, undergoes only normal rearrangement, and the reason for this is explored. Ionisation constants, ultraviolet, and nuclear magnetic resonance spectra are used to follow the rearrangements or confirm the structures involved.