Ring Expansion of Thiochroman-4-one and Isothiochroman-4-one with Ethyl Diazo(lithio)acetate to Tetrahydro-benzothiepin-*-oxoesters

When thiochroman-4-one (1 ) and isothiochroman-4-one (3) were treated with ethyl diazo(lithio)acetate, ethyl 2,3-dihydro-4-hydroxy-1-benzothiepin-5-carboxylate (2) and ethyl 1,3-dihydro-4-hydroxy-2-benzothiepin-5- carboxylate (4), respectively, were formed. An improved procedure for the two-step addition-ring expansion sequence is described. The preparation of 2.3-dihydro-1 -benzothiepin-4(5H)-one (7) and of 1.3-dihydro-2- benzothiepin-4(5H)-one (8) from the esters (2) and (4), respectively, is reported. Deoxygenation of (7) and (8) to 2,3,4,5-tetrahydro-1 -benzothiepin (9) and 1,3,4,5-tetrahydro-2-benzothiepin (1 0) by Caglioti reduction is described.