Study On The Synthesis Of Benzo Heterocyclic Compounds Based On O-isothiocyanato-(E)-cinnamaldehyde

Benzothiazine and quinazoline compounds are two kinds of important benzo heterocyclic compounds.Their unique chemical properties and biological activity have attracted the interest of a large number of pharmacists and chemists.Based on reseach progress in synthesis of benzothiazine compounds and quinazoline compounds in recent years,we propose two new synthetic routes:(1)By catalyst controlling the reaction between o-isothiocyanato-(E)-cinnamaldehyde and primary amine,we can efficiently synthesize 3,4-dihydroquinazolin-2(1H)-thione derivatives or selectively synthesize 4H-benzo[d][1,3]thiazine-2-amine derivatives;(2)By catalyzing o-isothiocyanato-(E)-cinnamaldehyde with hydroxylamine hydrochloride,we can obtain 1H-benzo[d][1,3]thiazine-2(4H)-one derivativesIn this paper,a series of 3,4-dihydroquinazolin-2(1H)-thione derivatives were synthesized via the domino reaction of o-isothiocyanato-(E)-cinnamaldehyde and primary amine.When the aldehyde group of o-isothiocyanato-(E)-cinnamaldehyde is protected firstly,thiourea intermediate could be obtained stably through the reaction with primary amine.The intermediate can be further cyclized to get 4H-benzo[d][1,3]thiazine-2-amine derivatives under reflux conditions.The one-pot can greatly improve the efficiency of reaction.Therefore,we propos a new method for constructing structurally diverse compound collections from identical substrates.The method is easy to operate and the yield is excellent.The method also has good chemical selectivity and functional group compatibility.Subsequently,we use hydroxylamine hydrochloride instead of primary amine to react with o-isothiocyanato-(E)-cinnamaldehyde.This rection can construct structurally diverse compounds,and we have obtained 1H-benzo[d][1,3]thiazine-2(4H)-one derivatives.The absolute configurations were determined by the single-crystal X-ray analysis.