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32.5.2.1.1.1 Variation 1: Kinetic Deprotonation of a Ketone

DOI: 10.1055/sos-SD-032-00588

Trauner, D.Science of Synthesis, (200832549.

The deprotonation of ketones can often be achieved with a high level of control. Regioselectivity issues arise when unsymmetrical ketones have α-protons available on both sides of the carbonyl group. These can be overcome by deprotonating under kinetic or thermodynamic conditions. Kinetic enolates are formed by deprotonation at the least-hindered and kinetically most-acidic site, which usually leads to less substituted and thermodynamically less stable enolates. In the case of enones and vinylogous esters, the position next to the carbonyl group undergoes faster deprotonation under kinetic conditions (α- vs γ-deprotonation). The regioselective formation of kinetic enolates has been studied and reviewed in great detail, and some examples are given in Scheme 3.[‌6‌‌9‌]

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Meeeee 8 Meeeeee Meeeeeeeeeeee ee Meeeeee[‌8‌‌8‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeeeeeeeee-8(8M)-eee (8); Meeeeee Meeeeeeee:[‌8‌]

M eeee ee MMM (88.8eeee) ee eeeeeee (88eM) eee eeeeeee eeee MMM (888eM) eee eee eeeeeeeee eeeeeee eee eeeeee ee 88°M. Mee eeeee eeeeee 8 (8.88e, 88.8eeee) ee MMM (88eM) eee eeeee eeeeeeee ee eeee eeee eeee e 88-eee eeeeee, eeee eeeeeeee eee eeeeeeeee eeeeeee. Mee eeeeeeeee eeee eee eeeeee ee eee eeeeeee eeeee eeee 88eee, eeeeeeee eee 8e, eee eeeeee ee ee. Mee eeee eee eeeeeeee eeee ee MM8Me eee eeeeeeeee eeee Me8M. Mee Me8M eeeeeeee eeee eeeeee eeee ee MeMMM8 eee eeeee, eeeee, eee eeeeeeeeeeee. Mee eeeee eeeeeeee eee eeeeeeeee ee eeeeeee eeeeeeee; eeeee: 8.88e. Meeeeee eeeeeeeeeeee ee eeeeeeeeeeeeee eeeeeeee eeee eeeee-eeeeee; eeeee: 8.88e (88%); eee eeee eee-eeeeee; eeeee: 888ee (88%).

(8eM,8M,8M,8eM)-8-(eeee-Meeeeeeeeeeeeeeeeee)-8-(eeeeeeeeeeeeeee)-8,8e,8,8,8,8e-eeeeeeeeeeeeeeeee-8-ee Meeeeeeeeeeeeeeeeeeeeeeee (88) eee (8eM,8M,8M,8eM)-8-(eeee-Meeeeeeeeeeeeeeeeee)-8-(eeeeeeeeeeeeeee)-8,8e,8,8,8,8e-eeeeeeeeeeeeeeeee-8-ee Meeeeeeeeeeeeeeeeeeeeeeee (88):[‌8‌]

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References


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