Phenothiazine,a linearly fused nitrogen-and sulfur-containing tricyclic compounds,has been become one of the most important heterocycles due to its valuable chemical properties and significant biological activities.It has been reported that at least one hundred phenothiazine derivatives were used in therapy mainly as neuroleptics.On the other hand,phenothiazine and its derivatives are promising materials for use in light-emitting diodes,photovoltaic cells,organic integrated circuit sensors,and driving circuits for large-area display devices.1The developing efficient construction methodologies of diverse phenothiazines is one of the hottest research topics in organic and medical chemistry in recent years.Alkyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetates belong to a class of cyclic β-enamino ester,which could be easily generated by the cyclization of o-aminobenzenethiol with methyl 4-chloroacetoacetate,have been found important applications for the synthesis of various functionalized or fused [1,4]thiazines.2The 2,3,4,7-tetrahydrobenzo[c]phenothiazines and 7,9,10,12-tetrahydrobenzo[b]phenothiazines can be selectively synthesized from three-component reaction of aldehyde,1,3-diketones and cyclic β-enamino ester in refluxing AcOH/CH3CN medium or in refluxing acetic acid.On the other hand,the reaction of aromatic aldehyde with methyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetate in AcOH/CH3CN medium resulted in the polycyclic 8,14-methanobenzo[2,3][1,4]thiazocino[6,7-a]phenothiazines in satisfactory yields.