Cu(I)‐catalyzed asymmetric chlorination of β‐keto esters in the presence of chiral phosphine‐schiff base type ligands

Abstract

Chiral phosphine-Schiff base type ligand L8 prepared from (R)-(-)-2-(diphenylphosphino)-1,1'-binaphthyl-2'-amine was found to be a fairly effective ligand for Cu(I)-promoted enantioselective chlorination of β-keto esters to give the corresponding products in high yields and with moderate enantioselectivities.

Asymmetric Chlorination of β-Keto Esters Using Diaminomethylenemalononitrile Organocatalyst

“…Benzyl (S)-2-Chloro-1-oxo-2,3-dihydro-1H-indene-2-carboxylate (7c) 12,24) Enantiomeric excess was determined by HPLC with ChiralPak OD-H column (hexane-2-propanol=70 : 30), flow rate=0.7 mL/min; λ=254 nm; t minor =8.7 min, t major =9.7 min.…”

“…Several research groups have reported on the asymmetric chlorination of β-keto esters using metal catalysts. [6][7][8][9][10][11][12][13][14][15][16][17] Organocatalysis, meanwhile, has received considerable attention in the area of organic synthesis because, in comparison to reactions involving metal catalysts, it is an environmentally benign method. Synthetic methods for producing α-chlorinated compounds from β-keto esters using organocatalysts have also been developed.…”

“…The highly stereoselective (>80% ee) α-chlorination of simple esters of 1-oxo-2,3-dihydro-1H-indene-2-carboxylic acid, such as methyl, ethyl, and benzyl esters (6a-c), is very rare. 12,18) Among the various chlorine sources, NCS is one of the best reagents because of its simple structure and low cost. The α-chlorination of a simple cyclic β-keto ester with NCS, in the presence of an organocatalyst (ca.…”

Catalytic Strategies for the Asymmetric Construction of Cyclic Frameworks with a Halogenated Tetrasubstituted Stereocenter

“…To further expand the diversity of the chiral ligands for the asymmetric halogenation, Shi and co‐workers prepared a series of axially chiral phosphine‐Schiff base as ligands, and examined the catalytic activities. Results showed that L10‐ Cu(I) complex was the optimal catalyst for the asymmetric chlorination of β‐ keto esters, and the desired products were obtained in good yields with moderate enantioselectivities (Scheme b) …”

Catalytic Enantioselective α‐Chlorination of Carbonyl Compounds

“…As summarized in Table 1, several other Lewis acid catalysts have been presented for the enantioselective chlorination of b-keto esters. [12][13][14][15][16][17] The desired products were obtained with good-to-high enantioselectivity for cyclic substrates, but no successful example involving acyclic b-keto esters was provided in these reports. On the other hand, it has been shown that a zinc(II) complex with the DBFOX ligand efficiently catalyzes the asymmetric chlorination of both cyclic and acyclic b-keto phosphonates to give the corresponding a-chloro-b-keto phosphonates with good-tohigh enantioselectivity (Scheme 11).…”