[3+3] Cyclocondensation of β-carbonyl-substituted 1 H -benzo[ f ]chromenes with 3-amino-1,2,4-triazoles: synthesis of [1,2,4]triazolo[1,5- a ]pyrimidines

The reaction of β-carbonyl-substituted 1 H -benzo[ f ]chromenes with 3-amino-1,2,4-triazoles provides a new avenue for the preparation of [1,2,4]triazolo[1,5- a ]pyrimidines containing a (2-hydroxynaphthalen-1-yl)methyl group at position 6. The reaction of 2-trifluoroacetyl-1 Н -benzo[ f ]chromene with 3-amino-5-(methylsulfanyl)-1 H -1,2,4-triazole yielded a derivative of a new 4,5,5a,13a-tetrahydro-6 H -benzo-[5,6]chromeno[3,2- e ][1,2,4]triazolo[1,5- a ]pyrimidine heterocyclic system. The proposed cascade reaction mechanism includes an aza-Michael reaction, cyclodehydration, and a retro-oxa-Michael reaction.