Microwave assisted synthesis of 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d] pyrimidin-4-ones by radical addition of 2-hydroxy-4H-benzo[4,5]thiazolo[3,2-a] pyrimidin-4-ones to various conjugated alkenes and dienes mediated Mn(OAc)3

Abstract

Synthesis of chemically important, novel 2,3-dihydro-4H-benzo [4,5]thiazolo [3,2-a]furo [2,3-d]pyrimidin-4-one derivatives was approached in this work. These heterocyclic compounds were synthesized in good to excellent yields from the reaction of Mn(OAc)3 mediated radical addition of 2-hydroxy-4H-benzo [4,5]thiazolo [3,2-a]pyrimidin-4-one (1a-1f) derivatives to various conjugated alkenes (2a-2e, 2h) and dienes (2f, 2g, 2i) under microwave irradiation in mild conditions. Also, a different compound skeleton, 2,3-dihydrobenzo [4,5]imidazo [1,2-a]furo [2,3-d]pyrimidin-4(10H)-one 3α (90%), was obtained from the reaction of 2-hydroxy-10-methylbenzo [4,5]imidazo [1,2-a]pyrimidin-4(10H)-one (1g) and 1,1-diphenylethylene (2h) for the first time. While no product was obtained with conventional method in radical addition reactions, dihydrofuropyrimidines (3a-z, 3α) were synthesized in excellent yields using microwave irradiating method at 150 °C, 350 W for 60 s. All isolated compounds were characterized by spectroscopic techniques (FTIR, 1H NMR, 13C NMR and 19F NMR) and HRMS analysis.