Reaction of 2,3‐dihydro‐1,5‐benzothiazepines and phenylacetyl chloride in the presence of triethylamine: A new aspect on the formation mechanism of dihydro‐1,3‐oxazin‐4‐one derivatives

2a,CDisubstituted 2,2a,3,4‐tetrahydro‐2‐phenyl‐1 H ‐azeto[2,1‐ d ][1,5]benzothiazepin‐1‐ones, as well as 2‐substituted 2.3‐dihydro‐3‐phenylacetyl‐2‐styryl‐benzothiazoles and 4a,6‐disubstituted 3‐benzyl‐4a,5‐dihydro‐2‐phenyl1‐H,6H‐[1,3]oxazino[2,3‐d][1,5]benzothiazepin‐l‐ones, were obtained from the reaction of 2,4‐disubstituted 2,3dihydro‐1,5‐benzothiazepines with phenylacetyl chloride in the presence of triethylamine. The mechanism for the formation of 4a,5‐dihydro‐1 H ,6H‐[1,3]oxazino[2,3‐d][1,5]benzothiazepin‐1‐ones, 2,3‐dihydro‐1,3‐oxazin‐4‐one derivatives, was suggested.