Alcohols acyl compounds

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]. 

Some distinctive features of the insertion reactions reported in Table VII can be summarized as follows First, carbon monoxide gives rise by insertion (5, 195a) to acyl bonds which are easily cleaved by water, alcohols, or compounds with mobile hydrogen. The metal is thus easily removed from the organic part and, being eliminated in its reduced state, can undergo a further oxidative addition, leading to a catalytic cycle. Thus, use of CO is very favorable for catalytic reactions. 

When an acyl group replaces the hydrogen of alcohols, carboxylic acids, hydrogen halides, ammonia or amines, we have the acyl compounds known as esters, anhydrides, halides, and amides, respectively. 

Although more rare, the ring opening of A-acyl (3-lactams has also been realized by using hydrides, giving rise to the corresponding reduction products. In this context, Scheme 40, Lee and Pak [107] have described the treatment of A-Boc (3-lactam 119 with lithium aluminium hydride to give A-protected amino alcohol 120. Compound 120 could serve as potential intermediate for the synthesis of various hydroxylated indolizidine alkaloids. 

Amphoteric compounds such as amino acids can be resolved as acid or amine forms after deriving corresponding esters or N-acyl compounds. Racemic alcohols and amines are also resolved by use of optically active isocyanates, where the alcohols and amines are derived the corresponding diastereomeric urethanes or ureas. 

In carbohydrate trityl ethers and the partially acylated carbohydrate derivatives obtained from them, the free hydroxyl groups may be etheri-fied with other alcohols. This method has been used repeatedly, particularly for the preparation of partially methylated compounds. With the alkali resistant trityl ethers, any alkaline alkylation method may be used, for example, dimethyl sulfate and alkali, or methyl iodide and silver oxide. In choosing an alkylation method for partially acylated compounds, one must be selected which does not cause acyl migration or saponification. 

In a series of papers [23], Tamai et al. reported using l,r-binaphthyl isomers as templates for a diastereoselective synthesis of ester alcohols from the corresponding acyl compounds. They reported a low d.e. of 16% of the ester alcohol [Eq. (8) 23c]. However, their more recent modifications gave improved yields and higher diastereoselectivities. When they added a polyether as a 2 -substituent and lengthened the chain between the dicarbonyls, the 7 -isomer was formed exclusively. Hydrolysis of this product yields the / -lactone. The authors suggest that the cooperative chelation of the oxygen side chain plays an important role in the exclusive formation of the / -enantiomer. 

The C-acyl compounds 320 underwent hydration on being heated in aqueous alcohol, but the resulting unstable azacyclols 321 underwent retroaldol fission and afforded the ring-opened derivatives 322. ° When the reaction was carried out in deuterium oxide or in labeled water, the incorporation of deuterium in the position a to the RCO group or of 0 into the ureido carbonyl group was observed. ... 

The lipase-catalysed enantioselective acylation of allylic alcohols in an ionic liquid solvent was demonstrated by Itoh et al. [16] (Fig. 7.7). They found that the acylation rate was strongly dependent on the counter anion of the imidazolium salt, while the lipase-catalysed acylation proceeded with high enantioseleclivity in all ionic liquid tested. Good results were obtained when the reaction was carried out in [bmimT [PFg ] or [bmun" ][BF ]. Other examples of kinetic resolution of allylic alcohols catalysed by lipases in ionic liquids were also reported by these authors [71, 72]. The transesterification of 5-phenyl-l-penten-3-ol under reduced pressure at 27 hPa and 40°C was carried out using methyl phenylthioacetate as acyl donor in [bmim+] [PF ] and [bdmim ][BF ], for obtaining the corresponding acylated compound in optically pure form [71], The acetylation of methyl mandelate catalysed by immobilised P5L in [bdmim ][BF ] is another example reported by these authors about the successful application of ionic liquids as reaction media in racemic resolutions... 

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. 

FIGURE 18.42 By analogy to what we know of other acyl compounds, we might well expect the treatment of an amide with a metal hydride to result in the formation of an alcohol. In fact, this reaction does not take place. An amine is formed instead. 

Syntheses of ketones from alcohols Acylation of carbonium ions by Reissert compounds... 

Finally, we comment that PTR-MS has been used to draw a link between the volatile compound release and the genetic factors through the emission of various esters from cultivated strawberries [65]. Esters, which are produced via esterification of alcohols in the presence of acyl-CoA by the enzyme alcohol acyl-transferase (AAT), are among the most important constituents of a strawberry aroma and are largely responsible for the sweet smell associated with strawberries. By detecting the esters in the headspace above strawberries by PTR-MS, a correlation was found between the expression of an AAT gene, total AAT activity, and the presence of esters. The PTR-MS data presented in this work represented a subset of a major data set collected over a 3-year period (2002-2004) to characterize the fruit quality of strawberry genotypes in northern Italy. 

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