Unsaturated carboxylic esters acylation

In 2006, Zeitler demonstrated the use of alkynyl aldehydes in redox esterification [114]. As in previous examples, the author proposes the formation of an activated carboxylate that acts as an acylating agent Eq. 19. A variety of a,P-unsaturated carboxylic esters 199 are formed in moderate yields with E-selectivity up to >95 5. 

Conjugate hydrocyanation of oc -unsaturated carboxylic esters, acid chlorides, and acyl cyanides, is effected by reaction with diethylaluminium cyanide [e.g. (128) — (129)]. The acid chloride and cyanide are the most reactive. A double conjugate addition of nitromethane with a 2-methylene-4-en-3-one (130) gave a... 

The addition of acyl hydrazides to (l,2-alkadiene)phosphonic diamides (325) yields the 1,2,3-diazaphospholidine 3-oxides (326). Interaction of the phospho-nite esters (327) (X = Cl or Br) with a,P-unsaturated carboxylic esters, nitriles, ketones, or related compounds, gives quaternary products which decompose in boiling benzene to produce the dihydrophospholes (328). ... 

Phenol esters of a,(3-unsaturated carboxylic acids have an interesting reactivity due to the synthetic utility of the resulting hydroxychalcones (Scheme 19). This aspect will be illustrated in Section IV. However, from the basic point of view, it is worth mentioning that the cis or trans configuration of the olefinic part of the acyl moiety can have a marked influence on the photochemical reactivity of the ester. When para-methoxyphenyl fumarates are irradiated, the normal ortho-rearranged products are obtained. By contrast, irradiation of para-me-thoxyphenyl maleates does not lead to rearrangement. Instead, cyclization products are obtained (Scheme 20). 

Carboxylic acids and their derivatives like esters, amides, anhydrides, and acyl halides are formally synthesized from olefins, carbon monoxide, and compounds represented by Nu-H such as H2O, ROH, RNH2, RCOOH (Equations (4) and (5)). Alkynes also react under similar conditions to afford the corresponding unsaturated carboxylic acid derivatives. These reactions have been named hydrocarboxylation, hydroalkoxycarbonylation, and hydroaminocarbonylation. 

Camphor-10-sulfonic acid (1) is available in large quantities in both enantiomeric forms. In only 3 steps the cyclic sulfonamide 2 (sultam) can be synthesized, which can be acylated with acid chlorides after deprotonation with sodium hydride (Scheme 1) [1, 2]. The resulting amides 3 are considerable more reactive towards nucleophiles than the corresponding carboxylic esters and the a,/ -unsaturated derivatives undergo, with excellent selectivities, Diels-Alder reactions or Michael additions under mild conditions. Al-... 

Acylation of a simple thiol with an alkyl carboxylate is not a very suitable method for preparation of S-alkyl thiocarboxylates. Transesterification is, however, possible if either the thiol or the carboxylic ester is activated. The enhanced reactivity of boron, aluminum and silicon thiolates has been utilized for the synthesis of a large variety of thiocarboxylic S-esters, including hydroxy derivatives (from lactones). a,P-Unsaturated thiol esters, e.g. cinnamoyl or 2-butenoyl derivatives, are also accessible. Michael addition, an undesirable side reaction of thiols, is completely avoided if alkyl trimethylsilyl sulfides ortris(arylthio)boranes are applied. ... 

Nucleophiles react with a, 8-unsaturated carboxylic acid derivatives with reactive carbonyl groups, such as acyl chlorides, to form nucleophilic acyl substitution products. Conjugate addition products are formed from the reaction of nucleophiles with less reactive carbonyl groups, such as ester and amides. 

So far we have shown you conjugate additions mainly of a,P-unsaturated aldehydes and unsaturated a,P-ketones. You won t be at all surprised to learn, however, that unsaturated acids, esters, amides, and nitriles—in fact all carboxylic acid derivatives—can also take part in conjugate addition reactions. Two examples, an amide and an ester, are shown on the right below. But notice how the selectivity of these reactions depends on the structure of the unsaturated compound compare the way butyllithium adds to this a,P-unsaturated aldehyde and a,P-unsaturated amide. Both additions are irreversible, and BuLi attacks the reactive carbonyl group of the aldehyde, but prefers conjugate addition to the less reactive amide. Similarly, ammonia reacts with this acyl chloride to give an amide product that derives from direct... 

Shin, C., K. Nanjo, E. Ando, and J. Yoshimura a,p-Unsaturated Carboxylic Acid Derivatives. VI. New Synthesis of N-Acyl-a-dehydroamino Acid Esters. Bull. Chem. Soc. Japan 47, 3109 (1974). 

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