The stereochemistry and reactions of some 3,4-disubstituted thiochromans and related dihydronaphthothiopyrans

Abstract

Hydrolysis of trans-3,4-dihalogenthiochromans, trans-1,2-dibromo-2,3-dihydro-1H-naphtho[2,1-b]thiopyran, and trans-3,4-dibromo-3,4-dihydro-2H-naphtho[1,2-,b]thiopyran yielded 2-hydroxymethylbenzo[b]thiophen, 2-hydroxymethylnaphtho[2,1-b]thiophen, and 2-hydroxymethylnaphtho[1,2-b]thiophen, respectively. Borohydride reduction of 3-halogenothiochroman-4-ones and related bromodihydronaphthothiopyranones gave cis-3-halogenothiochroman-4-ols and the corresponding cis-bromodihydronaphthopyranols. The ¹H n.m.r. spectra of these compounds show that the hetero-ring adopts the ‘sofa’ conformation, with both substituents axial in the trans-isomers, and that the most stable conformation of the cis-isomer is that in which the substituent at the benzylic position is pseudo-axial.