(4R)-4-hydroxy-3,4-dihydro-2H-1lambda6-benzothiopyran-1,1-dione synthesis

Yield:-

Reaction Conditions:

with methanol;potassium carbonate at 23; for 3 h;

Steps:

General procedure for the hydrolysis of (R)-2 acetyl esters

General procedure: To a solution of the corresponding (R)-2 (1equiv, 0.16mol) in methanol (300ml), potassium carbonate (3equiv) was added. The mixture was stirred for 3h at room temperature (23°C). Next, the mixture was filtered off and the filtrate was concentrated under reduced pressure. Water (300ml) was then added to the residue and this was extracted by ethyl acetate (3×200ml). The organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. Resulting crude material was purified by either vacuum distillation for (R)-1a and (R)-1d, or re-crystallization to give pure (R)-1 alcohol. (4R)-1,1-Dioxo-3,4-dihydro-2H-thiochromen-4-ol (R)-1e was re-crystallized from hexane-isopropanol (10:1). Mp=91°C. Yield-34%. IR bands: 3455, 2977, 2924. [α]20D=-7.0[α]D20=-7.0 (c 1.3, CHCl₃) for 94% ee {literature [α]25D=+5.1[α]D25=+5.1 (c 1.0, CHCl₃) for 99% ee of the (S)-isomer}.¹⁷

References:

Kucher, Olexandr V.;Kolodyazhnaya, Anastasiya O.;Smolii, Oleg B.;Boiko, Alexandr I.;Kubyshkin, Vladimir S.;Mykhailiuk, Pavel K.;Tolmachev, Andrey A. [Tetrahedron Asymmetry,2014,vol. 25,# 6-7,p. 563 - 567]