Chiral allenoates

Zhang et al. developed the enantioselective chiral phosphine-catalyzed addition of 2,3-allenoates with carbon-centered nucleophiles and electron-deficient olefins leading to efficient enantioselective C-C bond formation [248, 249]. 

Michael-aldol reaction as an alternative to the Morita-Baylis-Hillman reaction 14 recent results in conjugate addition of nitroalkanes to electron-poor alkenes 15 asymmetric cyclopropanation of chiral (l-phosphoryl)vinyl sulfoxides 16 synthetic methodology using tertiary phosphines as nucleophilic catalysts in combination with allenoates or 2-alkynoates 17 recent advances in the transition metal-catalysed asymmetric hydrosilylation of ketones, imines, and electrophilic C=C bonds 18 Michael additions catalysed by transition metals and lanthanide species 19 recent progress in asymmetric organocatalysis, including the aldol reaction, Mannich reaction, Michael addition, cycloadditions, allylation, epoxidation, and phase-transfer catalysis 20 and nucleophilic phosphine organocatalysis.21... 

Allenyl ketones can also be cross-coupled with allenoic acids to give 2,4-disubstituted furans <2002AGE1775> or with allenamides to yield 4-(3 -furanyl)-2(5//)-furanimines <2005JOC6291>. With chiral allenoic acid derivatives, 4-(3 -furanybbutenolides can be synthesized stereoselectively with complete chirality transfer (Equation 47) <2004CEJ2078>. 

Functionalized 2-hydroxy-3-allenoates can be converted into 2,5-dihydrofurans by using 5-10 mol% of gold(lll) chloride as catalyst. This mild and efficient cyclization method can be applied to alkyl- and alkenyl-substituted allenes at room temperature, furnishing tri- and tetrasubstituted dihydrofurans in good to excellent yields and with complete axis-to-center chirality transfer (Equation 50) <20010L2537>. 

The tertiary phosphine catalyzed [3+2] cycloadditions of allenoates 98 and electron-deficient olefins 99 was first discovered by Zhang and Lu [61] in 1995. Only two years later, the first enantioselective organocatalytic version of this reaction was reported by Chen and co-workers [62]. They showed that chiral phosphabicyclo[2.2.1]heptanes 100 catalyzes this reaction to give synthetically interesting optically active cyclopaitene derivatives 102 (Scheme 6.23). The mechanism for this reaction was later investigated... 

A review of formal aza-Diels-Alder reactions of imines with e-rich dienes and enones, in the presence of Lewis acids/Brpnsted acids/organocatalysts, has been presented. Bifunctional A-acyl aminophosphine catalysts (75) are effective asymmetric organocatalysts in the hetero-4- -2-cycloaddition of a-substituted allenoates with tosylaldimines to produce optically active tetrahydropyridines. The Brpnsted acid-catalysed aza-Diels-Alder reactions of cyclopentadiene with iminoacetates possessing two chiral auxiliaries yielded 2-azabicyclo[2.2.1]hept-5-ene cycloadducts with high exo-selectivities. ... 

Chen, D., Guo, L., Kotti, S. R. S. S., Li, G. (2005). The first asymmetric catalytic halo aldol reaction of (3-iodo allenoates with aldehydes by using chiral salen catalyst. Tetrahedron Asymmetry, 16, 1757-1762. 

Besides chiral amines, also phosphines, sulfides, A(-heterocyclic carbenes (NHCs), phosphoramides, and form-amides have been impressively utilized as chiral Lewis base catalysts in numerous case studies [14, 88]. Chiral phosphines have been mainly used for BayUs-Hillman-type reactions and allenoate activations in this context [88, 94]. 

Scheme 10.45 Enantioselective isomerization of 3-alkynoates to chiral allenoates.

In 2009, Tan and coworkers reported that the chiral bicyclic guanidine (S,S)-20 was able to catalyze the enantioselective isomerization of 3-alkynoates to chiral allenoates in what (formally) constitutes a 1,3-hydrogen sigmatropic rearrangement (Scheme 40.29) [33). The reaction took place in hexane at low temperature with high enantioselectivities, but conversions were not complete. 

Ao, Y.-R, Wang, D.-X., Zhao, L., and Wang, M.-X. (2014). Biotransformations of racemic 2,3-allenenitriles in biphasic systems Synthesis and transformations of enantioenriched axially chiral 2,3-allenoic acids and their derivatives. Journal of Organic Chemistry, 79, 3103-3110. 

A subsequent study by Jprgensen et al. also demonstrated the enantioselective a-sulfenylation of (S-dicarbonyl compounds 420 using l-alkylsulfanyl[l,2,4]triazole derivatives 419 in the presence of a catalytic amount of cinchona alkaloid derivative 421. The use of cyclic (S-dicarbonyl compounds ensured the introduction of a quaternary sulfur center however, the observed enantioselectivity was modest in 51-89%. In 2009, Zhu and co-workers reported that a chiral a,a-diaryl prolinol 424 efficiently catalyzed the enantioselective sulfenylation of (S-ketoesters 420 using N-(phenylthio)phthalimide 423 as a sulfur electrophile. The absence of racemizable C—H bonds led to the optically enriched a-sulfenylated products 425 in excellent enantio-selectivities. In 2010, Fu developed a method for catalytic asymmetric 7-sulfenylation of carbonyl compounds using 2,3-allenoates 426 in the presence of a chiral bisphos-phine, TangPhos 427, and a bulky carboxylic acid 428. ... 

Dinitrogen-fused heterocycles have been formed in high yield by thermal 3-1-2-cycloadditions of two types of azomethine imines with allenoates. Rhodium-catalysed formal 3 -l- 2-cycloadditions of racemic butadiene monoxide with imines in the presence of a chiral sulfur-alkene hybrid ligand have furnished spirooxindole oxazolidines and 1,3-oxazolidines stereoselectively. ° Formation of 1,2-disubstimted benzimidazoles on reaction of o-phenylenediamine with aldehydes is promoted by fluorous alcohols that enable initial bisimine formation through electrophilic activation of the aldehyde. 

A highly enantioselective [3 -f 2] cyclisation between diphenylphos-phinoyl imines (516) and allenoate (517) by employing the chiral phosphine (518) as catalyst has been developed by Lu and co-workers (Scheme 172). ... 

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