Synthetic applications of the photochemically induced addition of oxycarbinyl species to α-enones. Part I. The addition of simple alcohols

The photochemically induced conjugate addition of simple alcohols to a variety of α-enones has been investigated. With hex-2-enopyranosid-4-uloses (1), the alkylations occur from the less-hindered side and are completely stereo- and regioselective. The resulting 1,4-ketoalcohols (2) are readily cyclized to α-cyclopropyl ketones which have been prepared by alternative, less desirable routes. Alkylative additions of hex-1-enopyran-3-uloses occur also although less readily and without stereospecificity, giving C-glycosides. 2-Cyclohexenone and carvone are also photoalkylated by methanol giving moderate yields of the 1,4-ketols. In the case of carvone, carvone camphor was not detected as a by-product. Steroidal α-enones and mesityl oxide both fail to be photoalkylated by methanol.