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[摘要]：Good-to-excellent diastereoselectivies have been achieved in the synthesis of 2H-chromans by Et(3)SiH/TMSOTf reductive deoxygenation of differently substituted 2-sulfinyl-methylchroman-2-ols and their methyl ketals. The influence of both electron-donating and -withdrawing substituents on the sulfoxide and on the aromatic dihydobenzopyran core has been studied. SOR(1) electron-donating groups (R(1) = pMe-OPh and 2-MeO-1-naphthyl) led to a competitive reaction in which the sulfoxide was reduced, thus lowering the yield of the sulfinyl 2H-chromans. The method allows the presence of different groups on the aromatic dihydrobenzopyran unit. The best results in terms of yield and diastereoselectivity were obtained with 2-[(p-tolylsulfinyl)methyl]chroman-2-ols. All the results are explained on mechanistic grounds. Synthetic transformations of the enantiopure 2H-chroman (S,R(S))-21 are reported. |
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