Highly enantioselective and recyclable organocatalytic Michael addition of malonates to α,β-unsaturated aldehydes in aqueous media.
نویسندگان
چکیده
A new type of pyrrolidine-based organocatalyst, which was developed earlier in our lab, has been found to be very effective for the Michael addition reaction in aqueous solvents involving a wide range of α,β-unsaturated aldehydes and malonate derivatives. For the reactions studied, good to excellent yields (73%-96%) and high to excellent enantioselectivities (up to 97%) were obtained using this catalyst. In addition, the catalyst could be recycled up to four times with gradual reductions in yields and enantioselectivity observed after the second cycle.
منابع مشابه
Development of a general, enantioselective organocatalytic Mukaiyama-Michael reaction with α,β-unsaturated aldehydes.
LUMO-lowering organocatalysis has been extended to promote the conjugate addition of S-alkyl and -pyrrolyl silylketene acetals to α,β-unsaturated aldehydes, yielding both, syn and anti Mukaiyama-Michael products with high levels of enantioselectivity. This strategy allows for the generation of chemically useful 1,5-dicarbonyl systems and again highlights the utility of organocatalysis.
متن کاملA highly enantioselective, organocatalytic [3+2]-cycloannulation reaction towards the de novo-synthesis of 1-cyclopentenyl-α-keto esters.
We disclose herein a highly enantioselective de novo-synthesis of chiral 1-cyclopentenyl-α-keto esters starting from a simple bis-silyl-1,3-dienediolate and α,β-unsaturated aldehydes via a domino vinylogous Michael-intramolecular Knoevenagel-type condensation. The cyclopentenes proved to be highly versatile and were readily converted into various structural motifs.
متن کاملRole of quaternary ammonium salts as new additives in the enantioselective organocatalytic β-benzylation of enals.
We report herein the efficiency of quaternary ammonium salts as co-catalysts in organocatalytic Michael reactions involving iminium activation of α,β-unsaturated aldehydes. The enantioselective formal benzylation of these substrates has been optimized and used to rationalize the role of the ammonium salts in these processes.
متن کاملLight‐Driven Enantioselective Organocatalytic β‐Benzylation of Enals
A photochemical organocatalytic strategy for the direct enantioselective β-benzylation of α,β-unsaturated aldehydes is reported. The chemistry capitalizes upon the light-triggered enolization of 2-alkyl-benzophenones to afford hydroxy-o-quinodinomethanes. These fleeting intermediates are stereoselectively intercepted by chiral iminium ions, transiently formed upon condensation of a secondary am...
متن کاملEnantioselective γ-Alkylation of α,β-Unsaturated Malonates and Ketoesters by a Sequential Ir-Catalyzed Asymmetric Allylic Alkylation/Cope Rearrangement.
A catalytic, enantioselective γ-alkylation of α,β-unsaturated malonates and ketoesters is reported. This strategy entails a highly regio- and enantioselective iridium-catalyzed α-alkylation of an extended enolate, and a subsequent translocation of chirality to the γ-position via a Cope rearrangement.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Organic & biomolecular chemistry
دوره 10 41 شماره
صفحات -
تاریخ انتشار 2012