Application of β-(2-Chloroaroyl) Thioacetanilides in Synthesis: An Unusual and Highly Efficient Access to Thiochromeno[2,3-<i>b</i>]pyridine Derivatives
A series of unusual fused tricyclic thiochromeno[2,3-b]pyridines were successfully synthesized by tandem [3 + 3] annulation and SNAr of β-(2-chloroaroyl) thioacetanilides with activated 4-arylidene-2-phenyloxazol-5(4H)-ones or aromatic aldehydes and ethyl 2-cyanoacetate under microwave irradiation, respectively. Because of the existence of the o-chloro atom of β-(2-chloroaroyl) thioacetanilides, these