Chiral Phosphine-Free Pd-Mediated Asymmetric Allylation of Prochiral Enolate with a Chiral Phase-Transfer Catalyst

Abstract

[reaction: see text]. A chiral phase-transfer catalyst has been applied to the asymmetric allylation of the tert-butyl glycinate-benzophenone Schiff base with various allylic acetates for the first time to give the allylated products in good yields and with comparable to higher enantioselectivity than for asymmetric alkylation at the same temperature (91-96% ee) without any chiral ligands for coordinating to the palladium.

Influence of aromatic substituents on metal(II)salen catalysed, asymmetric synthesis of α-methyl α-amino acids

“…11 They can also be used in conjunction with achiral palladium complexes to induce the asymmetric allylation of enolates. 12 Recently, polymer supported 9,13 and oligomeric 14 versions of cinchona derived phase transfer catalysts have been developed and used for asymmetric amino acid synthesis. The catalysts have also been used under micellar conditions.…”

Catalytic Enantioselective Assembly of Homoallylic Alcohols from Dienes, Aryldiazonium Salts, and Aldehydes

“…High regio-and Z/E-selectivities were obtained for most of 4-substituted aryldiazonium salts investigated, with the exception of 4-methoxybenzenediazonium tetrafluoroborate (entries 1-4 and 6-10 versus 5). However,t he reaction conversion was considerably influenced by the electronic nature of the substituent (entries [1][2][3][4][5][6][7][8][9][10]. Forinstance,considerably lower yields were observed for the cases involving aryldiazonium salts bearing highly electron-deficient phenyl groups (entries [8][9][10].…”

“…However,t he reaction conversion was considerably influenced by the electronic nature of the substituent (entries [1][2][3][4][5][6][7][8][9][10]. Forinstance,considerably lower yields were observed for the cases involving aryldiazonium salts bearing highly electron-deficient phenyl groups (entries [8][9][10]. In addition, the substitution pattern had some impact on the selectivities,a s found in cases involving 2-, 3-and 4-acetylbenzenediazonium tetrafluoroborates (2h, 2l and 2m;entries 7, 11, and 12).…”

“…[7] Multicomponent and domino reactions are actually among the most significant strategies which turn out to be very conceptually close to ideal synthesis. [8] However,t he significance of either asymmetric multicomponent or domino processes for carbonyl allylation to access chiral homoallylic alcohols with high structural diversity has been much less recognized and hence they are highly desirable.H erein, we describe ah ighly regio-and stereoselective multicomponent carbonyl allylation reaction enabled by the combined catalysis [9] of ap alladium complex and chiral anion phase transfer, [10,11] thus allowing for ahighly efficient assembly of chiral homoallylic alcohols from easily accessible dienes,a ryldiazonium salts,a nd aldehydes (Scheme 1c).…”

Bis(allyl)di-μ-chlorodipalladium

“…129 A number of chiral ligands have been screened in the palladium-catalyzed alkylation of cyclohexenyl acetate. 134 The alkylation takes place with various allylic acetates in high enantioselectivity without any chiral ligands for coordinating to the palladium (eq 54). The use of Schiff bases derived from carboxylic and phosphonic esters has been shown to be an original route for the synthesis of the corresponding optically enriched α-amino acids as prochiral nucleophiles.…”