Selective mono, bis, and trisiminoformylation of 2,4,6‐trialkyl‐1,3,5‐triazines ‐ unusual enol acylenamine tautomerism of hydroxyalkenyl‐1,3,5‐triazines

Abstract

Abstract2,4,6‐Trialkyl‐1,3,5‐triazines 1 can selectively be mono, bis or trisiminoformylated by reaction with trismorpholinomethane 2 or chloromethylene iminium salts 3 (Vilsmeier reagents), with each alkyl substituent reacting with only one molecule of the electrophile. The resulting aminoalkenyltriazines 4, 5 and 6 are partially or fully hydrolysed to corresponding formylation products. The latter exist either in enol or in unusual acylenamine tautomeric structures 10, 12, and 13, depending on the number of enamine or enol units found in the molecule. Reaction of triazines 1 with chlorobenzylidene iminium salts 16 gives monoiminobenzoylation to enaminotriazines 17.