Heterocyclic compound studies. II. Synthesis of 1,4‐benzodioxin, 1,4‐benzoxathiin, 1,4‐benzoxazine and 1,4‐benzothiazine derivatives

Benzocondensed six‐membered heterocyclic rings containing two heteroatoms have been synthesized by a generally applicable method starting from disubstituted benzene compounds and methyl 4‐chlorobutynoate (1) or methyl 4‐bromobutenoate (2). The reactions with 1 yield a mixture of endo and exo (E or Z) isomers. The 13C nmr spectroscopy was used to assign the structure of the synthesized compounds.