Unsaturated carboxylic esters compounds

Two examples of Pd(II)-catalyzed carbomethoxylations of vinyl(phenyl)iodonium salts have been reported (equations 251 and 252)125,126. The mild reaction conditions and stereospecificity of carbonylation recommend further applications of vinyliodonium compounds for the synthesis of a,/ -unsaturated carboxylate esters. By way of comparison, similar carbobutoxylations of vinyl halides (Br, I) typically require higher temperatures (60-100 °C) and longer reaction times, and they sometimes proceed with low stereospecificity151. 

Some typical reactions of 1,1 -difluoroethene with nucleophiles are summarized in Scheme 2.18. Alkoxides [3], trialkylsilyl anion [4], ester enolates [5], and diphenylphosphinyl anion [6] attack the gem-difluorinated carbon of 5. However, it is noteworthy that nucleophilic substitution and proton abstraction are in some cases competitive, and thus s -butyl lithium abstracts the (3 -vinylic proton predominantly to generate vinyllithium. The lithium species can be trapped with an aldehyde, providing difluoroallyl alcohol, which is then hydrolyzed to a, (3-unsaturated carboxylic ester (11) [ 7 ] (Scheme 2.19). Some synthetically useful examples are shown in Schemes 2.20 and 2.21. Tetrathiafulvalene derivative (14) is prepared from difluorinated derivative (13) [8]. An elegant intramolecular version was demonstrated by Ichikawa, which provided a range of cyclized compounds (17), including dihydrofurans, thiophenes, pyrroles, and cyclopentenes, and also corresponding benzo derivatives (20) [2]. 

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). ... 

Formation of carboxylic acids ami their derivatives. Aryl and alkenyl halides undergo Pd-catalyzed carbonylation under mild conditions, offering useful synthetic methods for carbonyl compounds. The facile CO insertion into aryl- or alkenylpalladium complexes, followed by the nucleophilic attack of alcohol or water affords esters or carboxylic acids. Aromatic and a,/ -unsaturated carboxylic acids or esters are prepared by the carbonylation of aryl and alkenyl halides in water or alcohols[30l-305]. 

Reaction of a-sulphinyl carboxylic esters 421 with carbonyl compounds has usually been performed using a Grignard reagent as a base. No condensation products are obtained using t-butyllithium or sodium hydride367,496,497 (equation 251). The condensation products formed are convenient starting materials for the synthesis of a, p-unsaturated esters and /1-ketones497. 

Carboxylic Esters see also Dicarbonyl Compounds, Unsaturated Esters, etc.)... 

The benzotriazolyl derivative of acrolein acetal, compound 882, is lithiated, treated with chlorodiphenylphosphine, and the obtained intermediate is oxidized with hydrogen peroxide to phosphine oxide 883 (Scheme 145). The relatively acidic proton in derivative 883 is easily removed by a base, and the obtained anion adds to a carbonyl group of aldehyde or ketone. Subsequent rearrangement and elimination of the phosphorane group generates diene 884. For the derivatives of aldehydes (884, R2 = H), (E)-(E) stereoselectivity of the elimination is observed. Acidic alcoholysis of dienes 884 affords esters of P,y-unsaturated carboxylic acids 885 < 1997JOC4131>. 

During the coverage period of this chapter, reviews have appeared on the following topics reactions of electrophiles with polyfluorinated alkenes, the mechanisms of intramolecular hydroacylation and hydrosilylation, Prins reaction (reviewed and redefined), synthesis of esters of /3-amino acids by Michael addition of amines and metal amides to esters of a,/3-unsaturated carboxylic acids," the 1,4-addition of benzotriazole-stabilized carbanions to Michael acceptors, control of asymmetry in Michael additions via the use of nucleophiles bearing chiral centres, a-unsaturated systems with the chirality at the y-position, and the presence of chiral ligands or other chiral mediators, syntheses of carbo- and hetero-cyclic compounds via Michael addition of enolates and activated phenols, respectively, to o ,jS-unsaturated nitriles, and transition metal catalysis of the Michael addition of 1,3-dicarbonyl compounds. ... 

Catalysts suitable specifically for reduction of carbon-oxygen bonds are based on oxides of copper, zinc and chromium Adkins catalysts). The so-called copper chromite (which is not necessarily a stoichiometric compound) is prepared by thermal decomposition of ammonium chromate and copper nitrate [50]. Its activity and stability is improved if barium nitrate is added before the thermal decomposition [57]. Similarly prepared zinc chromite is suitable for reductions of unsaturated acids and esters to unsaturated alcohols [52]. These catalysts are used specifically for reduction of carbonyl- and carboxyl-containing compounds to alcohols. Aldehydes and ketones are reduced at 150-200° and 100-150 atm, whereas esters and acids require temperatures up to 300° and pressures up to 350 atm. Because such conditions require special equipment and because all reductions achievable with copper chromite catalysts can be accomplished by hydrides and complex hydrides the use of Adkins catalyst in the laboratory is very limited. 

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. 

Addition of organometallic compounds to unsaturated esters 5-20 Addition of tin and mercury hydrides to unsaturated ketones 5-22 Free-radical addition of carboxylic esters to olefins... 

Unsaturated Carbonyl Compounds 0-95 Vinylation of ketones or carboxylic esters... 

Heterosubstituted cyclopropanes can be synthesized from appropriate olefins and car-benes. Since cyclopropane resembles olefins in its reactivity and is thus an electron-rich car bo-cycle (p. 76ft). it forms complexes with Lewis acids, e.g. TiCL, and is thereby destabilized This effect is even more pronounced in cydopropanone ketals. If one of the alcohols forming the ketal is a silanol, the ketal is stable and distillable. The O—Si-bond is cleaved by TiCl4 and a d3-reagent is formed. This reacts with a -reagents, e.g. aldehydes or ketals. Various 4-substituted carboxylic esters are available from 1-alkoxy-l-siloxycyclopropanes in this way (E. Nakamura, 1977). If one starts with l-bromo-2-methoxycyclopropanes, the bromine can be selectively substituted by lithium. Subsequent treatment of this reagent with carbonyl compounds yields (2-methoxycyclopropyl)methanols, which can be transformed to /7,y-unsaturated aldehydes (E.J. Corey, 1975B). 

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