ENZYMATIC CYCLIZATIONS MEDIATED BY ULTRASONICALLY STIMULATED BAKERS-YEAST - SYNTHESIS OF IMIDAZO-FUSED HETEROCYCLES

o-Cyanophenyl allyl carbamate (3), 3-allyl-3,4-dihydro-4-imino-2H-1,3- benzoxazine-2-thione (8a), and -quinazoline-2(1H)-thiones (8b-d) have been cyclized to 2,3-dihydro-2-methyl-5H-imidazo[1,2-c][1,3]benzoxazin-5-one (5), the corresponding 5-thione (9a), and 2,3-dihydro-2-methyl-5H-imidazo[1,2-c] quinazoline-5(6H)-thiones (9b-d), respectively, by ultrasonically stimulated baker's yeast. The effect of ultrasound on the yeast cells employed for the enzymatic reactions has been investigated. It is observed that ultrasonic pretreatment of yeast cells not only accelerates the cyclization process but improves the yields significantly.