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Like the aldol addition, the Michael reaction may proceed via an enol, silyl enol ether in the Mukaiyama–Michael addition, or more usually, enolate nucleophile. In the latter case, the stabilized carbonyl compound is deprotonated with a strong base (hard enolization) or with a Lewis acid and a weak base (soft enolization).
The Mukaiyama aldol addition is a Lewis acid-mediated addition of enol silanes to carbonyl (C=O) compounds. In this reaction, compounds with various organic groups can be used (see educts). [3] A basic version (R 2 = H) without the presence of chiral catalysts is shown below. Simplified overview with a stereocenter
Silyl enol ethers are used in many reactions resulting in alkylation, e.g., Mukaiyama aldol addition, Michael reactions, and Lewis-acid-catalyzed reactions with S N 1-reactive electrophiles (e.g., tertiary, allylic, or benzylic alkyl halides).
It thus serves as a catalyst for Mukaiyama aldol reactions [2] and group-transfer chain-growth polymerization reactions. [3] As a Brønsted base, TTMPP can deprotonate various alcohols, giving nucleophilic alkoxides that can undergo Michael addition reactions. [4] TTMPP can act as a Michael nucleophile itself to catalyze Baylis–Hillman ...
The first two reactions shown below are from the syntheses of (+)-lycoflexine [32] and zaragozic acid C, [33] respectively, which are direct applications of Sakurai and Mukaiyama reactions. The third reaction, en route to (+)-fawcettimine, is a Lewis-acid catalyzed cyclopropane opening that is analogous to a Mukaiyama-Michael reaction. [34]
A Mukaiyama aldol addition (magnesium bromide / toluene) took place between aldehyde 7 and ketene silyl acetal 8 with 71% stereoselectivity to alcohol 9 which was protected as the TBS ether 10 (TBSOTf, 2,6-lutidine). The ester group was reduced with DIBAL to an alcohol and then back oxidized to aldehyde 11 by Swern oxidation.
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The Mukaiyama hydration is an organic reaction involving formal addition of an equivalent of water across an olefin by the action of catalytic bis ...