Allenyl carboxylic acid

The Pd-catalyzed reaction of propargyl electrophiles with carbon monoxide is a convenient route to allenyl carboxylic acid derivatives. In 1986, Tsuji et al. reported the Pd-catalyzed decarboxylation-carbonylation of propargyl carbonates under a CO at-... 

As early as 1940, Kohler and Whitcher reported the acid-catalyzed cyclization of 1,2-allenyl carboxylic acids [76],... 

Linkers that enable the preparation of y-lactones by cleavage of hydroxy esters from insoluble supports are discussed in Section 3.5.2. Resin-bound y-lactones have been prepared by Baeyer-Villiger oxidation of cyclobutanones [39], by intramolecular addition of alkyl radicals to oximes [48], by electrophilic addition of resin-bound sele-nenyl cyanide or bromide to 3,y-unsaturated acids (Figure 9.2 [100]), and by palladium-mediated coupling of resin-bound aryl iodides with allenyl carboxylic acids (Entry 10, Table 5.7 [101]). 

Marshall et al. very successfully applied this principle to the synthesis of natural products and extended it to allenyl carboxylic acids like 16 [16], which can lead to lactones like 17 (Scheme 6). 

Alkynylepoxides [123,142,143 Eq. (68) 142] and alkynyl propiolactones [Eq. (69) 144] afforded allenyl-alcohols or allenyl-carboxylic acids. Diastereoselective ring opening of alkynylepoxides has been studied [143,145]. The use of optically active propargyl substrates enables the synthesis of optically active allenes [Eq. (70) 146] [10,140,145-147]. A subtle change of the reaction medium may drastically change the degree of chirality transfer, which has been systematically examined [145]. 

A special type of Heck coupling was demonstrated vstith 1,2-allenyl carboxylic acids, which led to butenolides. Ma et al. [146] demonstrated a dramatic dependence of the reaction on the base and solvent used. In acetonitrile, intramolecular addition of the carboxylic acid to the adjacent allenic group proceeded without a subsequent Heck reaction. In toluene as solvent, especially in the presence of Bu4NBr, the desired butenohde was obtained. 

Toste has demonstrated the hydroalkoxycarbonylation of P-allenyl carboxylic acid derivatives catalyzed by a mixture of a chiral, enantiomerically pure bis(gold) complex and a chiral, enantiomerically enriched silver phosphonate salt [107]. As an example, treatment of 6-methyl-4,5-heptadienoic acid with a catalytic mixture of [(S)-binapj (AuC1)2 and Ag-(J )-67 formed the yluctone 83 in 88% yield with 82% ee (Eq. (12.43)) [107]. 

Several trivial but highly useful reactions are known to convert one acceptor-substituted allene into another. For example, the transformation of allenic carboxylic acids is possible both via the corresponding 2,3-allenoyl chlorides or directly to 2,3-allen-amides [182,185], Allenylimines were prepared by condensation of allenyl aldehydes with primary amines [199]. However, the analogous reaction of allenyl ketones fails because in this case the nucleophilic addition to the central carbon atom of the allenic unit predominates (cf. Section 7.3.1). Allenyl sulfoxides can be oxidized by m-CPBA to give nearly quantitatively the corresponding allenyl sulfones [200]. The reaction of the ketone 144 with bromine yields first a 2 1 mixture of the addition product 145 and the allene 146, respectively (Scheme 7.24). By use of triethylamine, the unitary product 146 is obtained [59]. The allenylphosphane oxides and allene-... 

Introduction 877 Alcohols as Nucleophiles 881 Allenyl Ketones 889 Allenic Carboxylic Acids 895... 

As indicated in Section ni.B, deprotonation of a carbamate affords a dipole-stabilized a-amino-organolithium that can be transmetalated with copper salts to form cuprates, thereby expanding the versatility of the organolithium. Suitable electrophiles include enones, alkenyl, alkynyl, allenyl and dienyl carboxylic acid derivatives, nitriles and sulfoxides. Dieter and coworkers have shown that the same process can be accomplished via transmetalation of a stannane (Scheme 36). The procedure is particularly... 

Enzymes such as pig liver esterase have been successfully applied in enantioselective hydrolysis of allenyl esters on a scale of 2 mmoles131. This provides the enantiomerically enriched allene-carboxylic acid as well as the ester of opposite configuration, by what is in fact a catalytic kinetic resolution (6-90% oy). Conversely, partial enantioselective esterification of /1-hydroxy-allenes (3-72% oy) employing lipases has been reported132,133. 

Other Studies. - The P NMR chemical shifts of alcohols, carboxylic acids and phenols phosphitylated with 2-chloro-4,4,5,5-tetramethyl-dioxaphospholane have been correlated with substituent effects of phenols. P NMR spectroscopy has also been used to study activation pathways of aryl H-phosphonate ester condensation reactions, the conversion of allenyl and divinyl phosphines to 1- and 2-phosphadienes, the reaction of tetraphosphorus decasulfide with dialkyl disulfides, the reaction of phosphine with cyclic olefins, the chemical shift tensors of powder samples of phosphole derivatives, the reactions of alcohols and mercaptans with tetraphosphorus trichalcogen diiodides, the structure of aminomethanebisphosphonic acids, and reactions of 00-di-(2-ethylhexyl)dithiophosphoric acids. ... 

Carboxylation. Under phase-transfer conditions, propargyl and allenyl halides in the presence of CO and Ni(CN)2 are converted into allenic acids. Further reaction gives rise to 2-alkylidenesuccinic acids. 

Species (30) derived from RCHO and CH2=C(Li)SEt are isomerized by acid to a-thiolated ketones.Oxidation to sulphoxide and elimination gives the unsaturated ketone. Allenyl analogues of the above reagent add to epoxides to give products which can undergo further useful synthetic modification. The Shapiro method for the generation of vinyl-lithiums from sulphonyl hydrazones has been applied to a new one-pot synthesis of a-methylene-y-lactones involving elimination and carboxylation of the trianionic intermediate (31). ... 

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