Wittig olefination-Claisen rearrangement

Synthesis of trifluoromethylated compounds 152 has been achieved via ester-enolate [2,3]-Wittig and [3,3]-lreland-Claisen rearrangements. Perfluorocyclo-butane phosphonium ylides, e.g. 153, have been used as a masked fluoride anion source in their reactions with alcohols and carboxylic acids which lead to alkyl-and acyl-fluorides. Ylides 153 are also reported to cleave Si-C and Si-O bonds, cause dimerisation of fluoro-olefins, and also react with acid chlorides or other activated aromatic compounds under halogen exchange. ... 

Dimethoxy-2(lH)-quinolines (235), which are key intermediates for the synthesis of antimalarial drugs, have been prepared in poor to moderate yields by intramolecular Wittig reaction of the salts (234). A combination of Wittig olefination and Claisen rearrangement of (2-hydroxy-4-prenyloxy)phenyl carbonyl compounds (236) has been used in a one-pot synthesis of 2, 3, 3 -trimethyl-2, 3 -dihydroangelicins (237). ... 

The synthetic route to 619 is a rather lengthy 27-step sequence outlined in Scheme 87 [192]. The first key reaction is a Wittig olefination of 606 with phosphorane 620 to give 621 with > 98% Z-selectivity. Subsequent Claisen rearrangement of the free alcohol 622 provides 623 with >98% stereoselectivity. Dieckmann condensation followed by decarboxylation gives the thermodynamically more stable ran -cyclopentanone 624 trans cis ratio = 7 1). 

Reviews have appeared on the use of the Wittig reaction in industrial practice, the Claisen rearrangement, synthetic applications of the retro-Diels-Alder reaction, organo-palladium intermediates for the alkylation and arylation of olefins, the Prins reaction to give 1,3-dienes, and intramolecular [4 + 2] (Diels-Alder) and [3 + 2] cycloadditions.An interesting discussion of the regiospecificity of the Diels-Alder reaction in terms of frontier orbital overlap favours the Woodward-Katz concept. Useful alkyne and polyene coupling reactions are described in reviews on the chemistry of vitamin the synthesis of insect sex... 

Ketals are converted to allyl vinyl ethers after Wittig olefination [14]. Wittig reactions permit the incorporation of various substituents into the allyhc terminal of the ether. Enol ethers have been conveniently prepared by cleavage of acetals with various Lewis acids. Cleavage of the ketals with the Lewis acid, for example, triethylsilyl triflate, in the presence of diisopropylethylamine in refluxing 1,2-di-chloroethane afforded the enol ethers (Eq. 3.1.9). The resulting enol ethers were then heated to effect the Claisen rearrangement without isolation. 

Claisen rearrangement Pd-catalyzed hydrogenation Diels-Alder reaction Wittig olefination cross coupling reaction... 

Begue JP, Bonnet-Delpon D, Wu SW, M Bida A, Shintani T, Nakai T. Claisen rearrangement of a-(E -aIkyl)enol ethers prepared via Wittig olefination of allyl perfluorolkanoates. Tetrahedron Lett. 1994 35 2907-2910. 

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