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26.9.1.1.7.2 Variation 2: Substitution by Addition/Rearrangement

DOI: 10.1055/sos-SD-026-00987

Marsden, S. P.Science of Synthesis, (2005261073.

The addition of hard nucleophiles to the carbonyl group of β-alkoxy enones, followed by acidic hydrolysis of the intermediate β-hydroxy enol ether, provides a complementary access to enones with transposition of the alkene and carbonyl functions compared with that given in Section 26.9.1.1.7.1. The method is particularly useful for the synthesis of substituted cyclohexenones. The addition of hydride leads to formal reduction/transposition of the enone, illustrated by the conversion of 139 into 140 (Scheme 31).[‌134‌] Alternatively, additional substituents can be introduced by the use of organometallic nucleophiles. Organolithiums are suitable nucleophiles and their high reactivity allows their introduction in sterically encumbered environments, such as adjacent to the quaternary center of 141 in the synthesis of enone 142.[‌135‌] Alternatively, Grignard reagents can be utilized, with the associated benefits in functional group compatibility such as the introduction of a halogenated aryl group to 143.[‌136‌]

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