Reduction of Vinylogous Thioesters with Lithium Aluminum Hydride. I. Reduction of β-Phenylthio-α, β-unsaturated Cyclic Ketones

Abstract

5, 5, Dimethyl-3-phenoxy-2-cyclohexenone (1b) was reduced with lithium aluminum hydride (LAH) to give the 1, 2-addition product (IIIa). 2-Methyl-3-phenoxy-2-cyclopentenone (IIa) gave a mixture of the allyl alcohol (IVa) and 1, 2-addition product (IVb). On the other hand, vinylogous thioesters, 5, 5-dimethyl-3-phenylthio-2-cyclohexenone (Ic) and 2-methyl-3-phenylthio-2-cyclopentenone (IIb) were reduced in ether to give the corresponding 1, 2-addition products. In tetrahydrofuran, the 1, 2-addition product (IIIb) from Ic was further reduced to the 3-phenylthio alcohol (VIa). The product (IVa) from IIb transformed on standing at room temperature into the vinyl sulfide (VII) and the enone (VIII).