Unsaturated carboxylic esters reaction

The prototype of a Knoevenagel reaction shown in the scheme above is the condensation of an aldehyde or ketone 1 with a malonic ester 2, to yield an a ,/3-unsaturated carboxylic ester 4. 

Preparation of l-ethoxy-2-phenyl-4,5-dimethoxycarbonyl-A2- 5-phospholene 1-oxide — Reaction of a vinylicphos-phonite diester with an unsaturated carboxylate ester... 

The reaction between a phenol and an unsaturated carboxylic ester has been widely used for the synthesis of chromone-2-carboxylic acids (00JCS1119,1179). There is little restriction on the substituents which may be present in the phenol and the necessary basic conditions have been achieved in various ways. 

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. 

Tetrahydro-7H-oxazolo[3,2-a]pyrimidin-7-ones (275) can be prepared from 2-amino-2-oxazolines and a,/8-unsaturated carboxylic esters. The orientation of the substituents in the reaction product corresponds to Michael addition of the oxazoline nitrogen as the first step (74LA593). 

The stereocontrol during asymmetric dihydroxylation reactions of /3,7-unsaturated carboxylic esters with trisub-stituted double bonds for the syntheses of 7-butyrolactones has been investigated in detail by Kapferer and Bruckner (Equation 87) <2006EJ02119>. 

The ate-complexes (34) also react with benzylic halides aroyl chlorides allyl halides and proj r l halides to afford the (x>rr ponding products, respectively (Eq. 75). (E)-a,P-Unsaturated carboxylic esters can also be obtains by the reaction of such borate complexes with ethyl propiolate The same type of reaction between copper(I) methyltrialkylborates and l-(l-pyrrolidinyl)-6-chloro--1-cyclohexene gives the corresponding alkylation products which are readily hydrolyzed to 2-alkylcyclohexanone... 

MO calculations have been carried out on the isomerization of cyclopropane to propene, and the MNDO method has been used to study the reaction pathway and to optimize the structure of reactant, transition structure, and product of the ring opening reaction of bicyclo[1.1.0]butane. Various methods have been employed to estimate the rate constants for ring opening of the 2-cyclopropyl-2-propyl radical. 1-Acceptor-1-sulfenyl-substituted 2-vinylcyclopropanes of the type (430) have been found to afford 6-sulfenyl-a,jS y, -unsaturated carboxylic esters and nitriles (431) upon treatment with acid, by a process which involves C(l)—C(2) bond fission and a novel 1,5-sulfenyl rearrangement (see Scheme 110). It has been shown that the benzophenone-sensitized photolysis of vinyl norcaradiene derivatives, such as 5-(2-methylprop-l-enyl)-3-oxatricyclo[4.4.0.0 ]deca-7,9-dien-4-ones (432), results in the regioselective cleavage of only one of the cyclopropyl c-bonds to afford isochroman-3-one derivatives (433). It has been reported that the major product obtained from the reaction of structurally diverse a-diazo ketones with an electron-rich alkene in the... 

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... 

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]. 

Reactions between diethyl hydrogenphosphonate and ArX (X = I or Br) to give diethyl arylphosphonates have been carried out in the presence of a phase transfer catalyst. Bis(trimethylsilyl) phenylphosphonite reacts with alkyl halides to give [(ar)alkylphenyl]phosphinic derivatives, and it also adds to a,P-unsaturated carboxylic esters (as well as to nitriles and amides) to give (2-functionalized-l-alkyl)phosphinic derivatives. ... 

Pyridopyrimidines of the [2,3-d], [3,4-d] and [4.,3-d] types may be prepared by reactions involving the cross-coupling of halogenopyrimidines with alkenes and alkynes. For example, 4,-amino-5-iodopyrimidines (298) with S-unsaturated carboxylic esters followed by ring-closure give the pyrido[2,3-d]pyrimidines (299)... 

Excellent stereoselectivities were observed in reactions of chiral 2-allylidene-l,3-dioxolanes derived from C-2-symmetric dioles with electron-deficient alkenes, such as a,P-unsaturated carboxylic esters or 7V-methyhnaleimide, in dichloromethane at room temperature. 

Finally, a different type of coupling reaction is achieved by molybdenum 0x0 complexes as catalysts. Aldehydes react with diazoacetate in the presence of PPhs to give a,jS-unsaturated carboxylic esters and Ph3P=0. Molybdenum carbene intermediates have been suggested (Scheme... 

The reaction was successfully applied to both electron-rich and electron-poor 4-nitrophenyl carboxylates among them, the conversion of the electron-deficient esters was found to be faster and more efficient. Many functional groups are tolerated on both the side of the carboxylic ester (halo, keto, formyl, ester, cyano, nitro and protected amino groups, heterocyclic and a,-unsaturated carboxylic esters) and of the alkene (electron-rich alkyl-substituted alkenes, electron-poor acrylate derivatives, trimethylvinylsilane as an ethylene surrogate). The cinnamate derivatives could become particularly useful substrates, since the availability of the synthetically equivalent vinyl halides is rather limited. In analogy to conventional Mizoroki-Heck chemistry, linear (Zi)-substituted alkenes are predominantly but not exclusively obtained. Selected examples are shown in Table 4.1. 

Preparation of y-Unsaturated Carboi lic Esters. Brown and Salunkhereported an analogous reaction involving ( )- or [Z)-1-aUcenyldichloroboranes and ethyl diazoacetate for the synthesis of, y-unsaturated carboxylic esters (eq 15). ... 

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