Methyl 3-oxo-3, 4-dihydro-2H-1, 5-benzoxathiepin-4-carboxylates (3a-f) were synthesized by regioselective Dieckmann reaction of methyl 2- methoxycarbonylmethylthiophenoxyacetates (2a-f)[readily prepared from 2-
[Cabiddu, Salvatore; Melis, Stefana; Sotgiu, Francesca; Cerioni, Giovanni Phosphorus and Sulfur and the Related Elements, 1982 , vol. 14, p. 151 - 156]