Synthesis and reactivity of some thiochroman-3,4-diones.

Thiochroman-3,4-diones, which result from the reaction of thiochroman-4-ones with isoamyl nitrite, form fused heterocycles on reaction with 1,2-diamines and with p-anisaldehyde and ammonium acetate. Cyclopenta-[c][1]benzothiopyran-2-one, formed on reaction with dibenzyl ketone, yields a dibenzo[bd]thiopyran after cycloaddition of DMAD. With methyl magnesium iodide, a mixture of thiochroman-3-and 4-ols is fomed which was separated only after the selective dehydration of the 4-ol. The resulting 4-methylene derivative was isolated as the hetero Diels-Alder spiro-liked adduct.