Alkenoic acids, synthesis

Coutrot, P., Snoussi, M., and Savignac, P., An improvement in the Wittig-Homer synthesis of 2-alkenoic acids. Synthesis, 133, 1978. 

Epoxidative lactonization.1 This reaction can be used for a diastereoselective synthesis of 5-hydroxyalkylbutanolides (3) from (E)- and (Z)-4-alkenoic acids (1). Thus epoxidation of (E)-l results in an epoxide (2) that in the presence of acid is converted into erythro-i. In contrast, (Z)-l is converted into threo-3. Yields are essentially quantitative. 

The authors gratefully acknowledge the financial support for this research by the Natural Sciences and Engineering Research Council of Canada. Tony Liu and Chris Maxwell thank the Student Work Experience Program at Queen s University for financial support during the summer of 2005. We acknowledge Farhad Nowrouzi for synthesis of a precursor to 4-chlorophenyl -4-pentenoic acid and for preliminary measurements of the e.e. for the reaction of 14- Br+ with some l,co-alkenols and alkenoic acids. 

Strategies centered on reductive introduction of the fluoroolefin via a geminal difluoro allylic array have been reviewed [66]. In an introductory example to this synthetic approach, Okada et al. [67] developed a completely stereoselective synthesis of Z)-2,5-syn 2-alkyl-4-fluoro-5-hydroxy-3-alkenoic acids through the Cu(l)-mediated allylic substitution reaction of trialkylaluminum with the (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative (61) (Scheme 21). Reaction... 

Synthesis oe Heterocyclic Compounds. In some cases, dehydroamino acids obtained from unsaturated 5(477)-oxazolones have been used as intermediates to prepare other heterocyclic compounds. For example, reaction of 2-benzoylamino-3-substituted-2-alkenoic acids 485 with alkyl or arylisothiocyanates affords 4-aryl-methylene-l,2-disubstituted-5-oxo-4,5-dihydroimidazoles 486 (Scheme 7.155). ... 

PIDA-mediated fragmentation reaction of tertiary cyclopropanols (117) afforded the corresponding alkenoic acids (118) in high yields [84]. This reaction was utilized for asymmetric total synthesis of a piperidine alkaloid, (-)-pinidine (119) [Eq. (28)]. 

Formation of a highly electrophilic iodonium species, transiently formed by treatment of an alkene with iodine, followed by intramolecular quenching with a nucleophile leads to iodocyclization. The use of iodine to form lactones has been elegantly developed. Bartlett and co-workers216 reported on what they described as thermodynamic versus kinetic control in the formation of lactones. Treatment of the alkenoic acid 158 (Scheme 46) with iodine in the presence of base afforded a preponderance of the kinetic product 159, whereas the same reaction in the absence of base afforded the thermodynamic product 160. This approach was used in the synthesis of serricorin. The idea of kinetic versus thermodynamic control of the reaction was first discussed in a paper by Bartlett and Myerson217 from 1978. It was reasoned that in the absence of base, thermodynamic control could be achieved in that a proton was available to allow equilibration to the most stable ester. In the absence of such a proton, for example by addition of base, this equilibration is not possible, and the kinetic product is favored. 

By this method (Z)-monounsaturated fatty acids and esters could be obtained with an ( )-isomer content of less than 10% this stereoselectivity being however inferior to that of the commonly used acetylenic approach 55,56). However, the salt-free techniques used today in Wittig reactions allow (Z)-alkenoic acids to be synthesized with less than 2% of the ( )-isomers. Thus, Bestmann et al. prepared methyl and ethyl esters of (Z)-4,5,6,7,8,9,ll- and 13-alkenoic acids of different chain lengths 35,57 62), which served as intermediates in the synthesis of insect pheromones, both by reaction of co-alkoxycarbonyl-substituted alkyl-triphenyl-phosphonium salts with simple alkanals and of co-formylalkanoic esters with alkylidenephosphoranes. As the starting material for the synthesis of -substituted alkyl-phosphonium salts co-chloro- and -bromocarboxylic esters were used. The corresponding -substituted aldehydes can usually be obtained by ozone cleavage of suitable olefin derivatives or by oxidation of alkohols 57,58). 

Among the fragrance and aroma substances a great variety of mono- and polyole-finic aliphatic alcohols, aldehydes, ketones, carboxylic acids, and their esters, as well as lactones are found 158). Of these aroma substances, (J5)-2-alkenals, ( )-2-alkenoic acids, ( )-2-alkenoic esters as well as (JS)-2-alken-l-ols are predestinated for the synthesis via the Wittig reaction because of the ( )-stereoselectivity of the olefination using resonance-stabilized ylides. 

Grison, Ph. C. C. and Sauvetre, R. (1987) 2-Diethoxyphosphoryl alkanoic acid dianions IV. A direct route to 2-fluoro-2-alkenoic acids by the Horner synthesis. Application in the field of pyrethroids. J. Organomet. Chem., 332, 1-8. 

Bernasconi, S. Comini, A. Corbella, A. Gariboldi, M. S., Activation of 2-Alkenoic Acids as Mixed Anhydrides with Diphenylphosphinic Acid for the Formation of Carboxamides. Synthesis 1980, 385. 

An example of the formation of an ester of an -4,5-alkenoic acid 164 comes in a synthesis of chrysanthemic acid by Ficini and her group.31 Reduction gives the allylic alcohol 163 and [3,3] Claisen rearrangement with triethyl ortho-acetate gives the product 164 in one step. 

Haloalkenes, CH2=CH-(CH2)nX (n = 3-7 X = Cl, Br), are interesting synthons for use in the preparation of long chain alkenols and alkenoic acids 2 in cyclization reactions,3 9 as intermediates in the synthesis of pheromones 10 11 in the preparation of silica gel having a functional surface 12 and for the synthesis of oo-iodochloroalkanes,13 and organogermanium dendrimers.14 They are usually prepared from the corresponding alkenols. 

Shortly thereafter, Ghosh and Liu" reported a convergent and enantioselective synthesis of 1183. In their strategy, macrolactonization of 1259 is the key step for assembling the core structure. Further disconnection of 1259 then revealed the oxazole dienylamine 1203 (R = CH3), D-alanine, and the 5-hydroxy-2-alkenoic acid 1228 as intermediate synthetic targets (Scheme 1.322). 

Rao, B.V.S.K., R Vijayalakshmi, and R. Subbarao, Synthesis of Long Chain (E)-3-Alkenoic Acids by the Knoevenagel Condensation of Aliphatic Aldehydes with Malonic Acid, J. Am. Oil Chem. Soc. 70 297-299 (1993). 

Analog of HTIB. Various derivatives of HTIB with substituents in the iodoarene nucleus, ArI(OH)OTs, and three arenesnlfonyloxy analogs have been reported. [Hydroxy (mesyloxy)Iodo] benzene, PhI(0H)03SMe, and [hydroxy((+)-10-camphorsulfonyloxy)iodo]benzene are also known. [Hydroxy ((bis (pheny loxy) phosphoryl) oxy) iodobenzene], PhI(0H)0P(0)(0Ph)2, shows considerable potential for phosphate ester synthesis. Thus far, the a-oxyphosphorylation of ketones and -dicarbonyl compounds, the oxyphosphoryllac-tonization of alkenoic acids, and the conversion of terminal alkynes to monoketol phosphates with HPIB have been reported. 

Kamekawa H, Senboku H, Tokuda M (1997) Facile synthesis of aiyl-substituted 2-alkenoic acids by electroreductive carboxylation of vinylic bromides using a magnesium anode. Electrochim Acta 42 2117-2123... 

Electrolysis of carboxylates in the presence of olefins may afford the radical addition products [5]. Intramolecular radical addition may furnish a simple and straightforward access to cyclic compounds. Mixed decarboxylative coupling of 6-alkenoic acids and various carboxylic acids giving cyclic compounds is utilized for synthesis of useful chemicals. For instance, a stereoselective synthesis of prostaglandin precursors is achieved successfully by mixed Kolbe-type decarboxylation [b](Fig.2). 

Metal-catalysed ring-opening reactions of lactones can be useful in synthesis. For example, a one-pot procedure for the formation of (Z)-4-alkenoic acids, the esters of which are components of various perfumes and flavours, relies on the cis nature of addition of dialkylcuprates to acetylenes to afford (Z)-alkenyl-cuprates. These cuprates induce ring opening of -propiolactone in a regioselec-tive manner by alkyl oxygen fission to give the desired compounds in excellent yield. ... 

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