THE ASYMMETRIC ALKYLATIONS OF CHIRAL TRANSITION METAL COMPLEXES OF(+)—CAMPHOR IMINE

The asymmetric alkylations of chiral transition metal complexes derived from (+)-camphor and 2-aminomethyl-6-methylpyridine were examined under mild conditions.The formation of the complexes 2 is conductive to the enhancement of di- astereoselectivity in the alkylations at room temperature.

Synthesis of chiral spirocyclo-quaternary ammonium salts from L-proline and their application as phase-transfer catalysts in asymmetric alkylation

A new series of chiral phase-transfer catalysts 7a-7h were designed and synthesized from L-proline with moderate to good yields.＇The catalytic activity of 7a-Th for the asymmetric alkylation of glycine Schiff bases was evaluated, and some interesting relationships between structure and catalytic activity were revealed.

Regioselective and asymmetric allylic alkylation of vinyl epoxides for the construction of allylic alcohols via synergistic catalysis

A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N'-dioxide/Ni~Ⅱ complex and an achiral Pd~0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enantioselectivity under mild conditions.Further transformations of the product demonstrate the potential utility of this protocol in the synthesis of allyl alcohol derivatives and natural product analogues.Experimental studies revealed that the N,N′-dioxide/metal complexes play an important role in controlling the Z/E-and enantioselectivity.The density functional theory(DFT) calculations further demonstrated that multiple C–H···π interactions between the aromatic rings of the two substrates and the amide moiety in the ligand stabilized the dominant transition state.

Asymmetric α-Alkylation of β-Ketocarbonyls via Direct Phenacyl Bromide Photolysis by Chiral Primary Amine

Enantioselective α-photoalkylation of β-ketocarbonyls without any external photosensitizer was described in this work. The photoalkylation reactions, enabled solely by a chiral primary amine catalyst, provided convenient constructions of all-carbon quaternary stereocenters with good activity and high enantioselectivity. Mechanism studies revealed α direct photolytic radical chain process under visible light irradiation.

Organocatalytic asymmetric allylic alkylation of sulfonylimidates with Morita-Baylis-Hillman carbonates

The asymmetric allylic alkylation reaction of sulfonylimidates with various Morita-Baylis-Hillman (MBH) carbonates was accomplished by the catalysis of commercially available cinchona alkaloids catalyst (DHQD)2AQN.The corresponding allylic alkylation products were obtained in good yields with high stereoselectivities (up to 99% ee,89:11 dr).

New Chiral N,S-Ligands with Thiophenyl at Benzylic Position. Palladium(II)-catalyzed Enantioselective Allylic Alkylation

bState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China cShanghai Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China New chiral N,S ligands with oxazoline and thiophenyl substituents at benzene ring and benzylic position have been prepared and applied in palladium catalyzed asymmetric allylic alkylation reaction to provide the product with high yield and entantioselectivity ( 82%-93% ee ).

Diastereoselective alkylation reactions employing a new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary

A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give a-alkylated carboxylic acids in good yield and in almost enatiomerically pure form.

A Formal Synthesis of (+)-Cassiol Exploiting Meyers' Bicyclic Lactam Methodology

A formal synthesis of (+)-cassiol using (1S,2S)-2-amino-1-(4-nitrophenyl)-1,3-propanediol as chiral auxiliary is reported. The quaternary chiral center in the molecule was constructed by sequential alkylation of a bicyclic lactam (prepared from the aforementioned auxiliary and 5-oxo-heptanoic acid) with methyl iodide and benzyloxymethyl chloride.