Ketones reaction with esters

Methylpyrazine reacts with sodamide in liquid ammonia to generate the anion, which may be alkylated to give higher alkylpyrazines (Scheme 10) (61JOC3379). The alkylpyrazines have found extensive use as fiavouring and aroma agents (see Section 2.14.4). Condensation reactions with esters, aldehydes and ketones are common, e.g. methyl benzoate yields phenacylpyrazine in 95% yield, and reactions of this type are summarized in Scheme 11. 

CpjZrClj, Zn, CHjBrj, THF methylenation of aldehydes, ketones no reaction with esters [714]... 

In the case of the benzothiazole system, both aldehydes and mixed ketones have been synthesized by reduction or alkylation of the appropriate carbonyl precursors. The carbonyl compounds are in turn prepared from the benzothiazole-2-anion either directly by reaction with esters or indirectly by reaction with aldehydes followed by PCC oxidation (Scheme 154) (85H2467 91BCJ3256). 

A-Alkylthiabenzenes are deprotonated by LDA and subsequent reaction of the anion with alkyl halides and ketones results in functionalization of the A-methyl group. However, reaction with esters leads to products arising from migration of the acylated methyl group (Scheme 108) <2000MI22>. 

The ate complex 99 also reacts more rapidly with ketones than with esters, as exemplified by the smooth reaction with levulinic acid ethylester 55 (>90% con-... 

Phosphoranes and phosphonate derived carbanions are also known to react with carbonyl compounds other than aldehydes and ketones, in reactions often referred to as non-classical Wittig reactions.35 Wittig olefination products can be obtained from the reaction of esters, anhydrides and some amides and imides with a range of stabilized and reactive phosphoranes. The reaction of stabilized and semi-stabilized phosphoranes with esters gives alkenes (Scheme 7). However, non-stabilized phosphoranes, such as methylenetriphenylphosphorane, tend to give P-keto phosphoranes on reaction with esters (Scheme 7)—the careful choice of the reaction conditions can also permit the preparation of the alkene in these reactions. 

Lateral metallation at C-2(a) of l-/ftt-butoxycarbonyl-2-methylimidazoline 709 (Scheme 173) with r f-BuLi results in the formation of a bright yellow lithiated intermediate that reacts with alkyl halides, diphenyldiselenide, and phosphoryl chlorides to give 710. In the case of reaction with esters, the conjugated ketones 711 are formed <2000T2061>. In the case of acylation with esters, conjugated enamino-ketones were the tautomer isolated. Further alkylation is also possible under similar conditions, to give 712. 

The reactions with esters of stabilized anions (32) and (38) give a-phenylthio ketones in yields of 75-82% (equation 37).2 Acylations with succinic anhydride and butyrolactone to give y-keto acids and y-hydiDxy ketones respectively, also proceed in good yields. ... 

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