Alcohols acylations

Alkyl- and arylmercury(II) halides are used for the ketone formation[402]. When active methylene compounds. such as /f-keto esters or malonates are used instead of alcohols, acylated / -keto esters and malonates 546 are produced, For this reaction, dppf is a good ligand[403]. The intramolecular version of the reaction proceeds by trapping the acylpalladium intermediate with eno-late to give five- and six-membered rings smoothly. Formation of 547 by intramolecular trapping with malonate is an example[404]. 

In general, reduction of amides to alcohols is difficult. More commonly the amide is reduced to an amine. An exception uses LiH2NBH3 to give the alcohol. Reduction with sodium metal in propanol also gives the alcohol.Acyl imidazoles are also reduced to the corresponding alcohol with NaBH4 in aqueous HC1. °... 

Notes A basic catalyst for amine and alcohol acylations, (particularly useful for hindered alcohols), macrocyclization, and for Steslich esterification. DMAPIPCC provides a useful oxidation protocol.1 Examples l.2... 

Alcohol Acyl chloride Ester Hydrogen chloride... 

The past decade has seen a large increase in the number of small molecule catalysts for asymmetric alcohol acylation. Representative members of virtually all... 

The redbanded leafroller moth uses a mixture of (E) and (Z) -11-tetradecenyl acetates as pheromone components. The pheromone gland of this insect also contains an acetyl Co A fatty alcohol acyl transferase (22.). This enzyme will acetylate 12, 14 and 16 carbon alcohols, and prefers the saturated alcohol to the Z monounsaturated derivative, and the Z to the E, in the approximate ratios of 5 3 1 for saturated, Z and E, respectively. 

In general reaction of an alcohol with the appropriate anhydride or acid chloride in pyridine at 0-20 JC is sufficient. In the case of tertiary alcohols, acylation is very slow in which case a catalytic amount of 4-dimethylaminopyridine (DMAP) can be added to speed up the reaction by a factor of 10,000. Reaction of polyols with acyl chlorides (1.2 equiv) in the presence of hindered bases (2.0equiv) such as 2,4,6-collidine, diisopropylethylamine or 1,2,2,6,6-penta-methylpiperidine in dichloromethane at -78 °C leads to selective acylation of a primary alcohol. Primary alcohols can also be acylated selectively with isopro-penyl acetate or acetic anhydride in the presence of a catalytic amount of 1,3-dichlorotetrabutyldistannoxane 325.1 [Scheme 4.325].602 The catalyst 325.1 is available commercially or can be easily prepared by simply mixing dibutyltin oxide and dibutyldichlorostannane. No aqueous workup is necessary since the catalyst can be removed by simple chromatography. 

El-Sharkawy, I., Manriquez, D., Flores, F.B., Regad, F, Bouzayen, M., Latche, A. and Pech, J.C. (2005) Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity. Plant Mol. Biol, 59, 345-62. 

Advantage can be taken of the enhanced polarity of a carbon-silicon bond over that of a carbon-hydrogen bond in the displacement of 2-tri-methylsilyl groups by reaction with a number of carbonyl reagents to give imidazoles substituted at C-2 by secondary alcohol, acyl, aroyl, ester, and amide functions. ... 

The intermediate 122 is a stable compound and can be made by any chemistry that gives simple alcohols. Acylation of 128 with a lactone gives the hydroxy ketone 132 and reduction gives the anti-diol 133 in excellent yield. Elimination gives pure -134, a pheromone of the Mediterranean fruit fly. 

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