L-Proline catalysed Michael additions of different methylene active compounds to α-enones in ionic liquid

Abstract

L-Proline catalysed Michael addition of different active methylene compounds to α-enones in [bmim]PF 6 was studied. Only 5 mol% of L-proline was necessary to achieve good yields of the products, but practically no stereoselectivity was observed. Reactions went smoothly with methyl vinyl ketone, benzylideneacetone as well as chalcone. Only medium yields of the product were isolated at additions to cyclohex-2-ene-1-one.

Synthesis and evaluation of guanidinyl pyrrolidines as bifunctional catalysts for enantioselective conjugate additions to cyclic enones

“…Although reasonable yields were obtained with catalysts 1 and 3 the enantiomeric excess was negligible (0-12%, Table 1, entries 1-6). In contrast, catalyst 2 provided (S)-4a with higher enantioselectivity 1, entries [12][13][14]. Also, with 2 as the catalyst, dibenzyl malonate provided higher enantioselectivity compared to its dimethyl 5b (4b, 59% ee) and diethyl 5b (4c, 52% ee) congeners whereas di-t-butyl malonate failed to react.…”

“…1. The conjugate addition of other carbon and heteroatom nucleophiles such as dibenzoylmethane, 13 malononitrile, 14 and naphthalene-2-thiol 15 was also effectively catalyzed with amino guanidine 2 to provide the conjugate addition products 6-8 respectively (Fig. 2).…”

“…IR spectra were recorded on a Bruker TENSOR 27 spectrometer. 1 H NMR and 13 C NMR spectra were recorded on a Bruker AVANCE-500 instrument. Coupling constants (J) are given in Hz.…”

Metal-Free Construction of Fused Pyrimidines via Consecutive C–C and C–N Bond Formation in Water

“…4 l -Proline possesses acidic (−COOH) and basic (−NH) moieties and catalyzed chemical transformations similar to enzymatic catalysis. 5 l -Proline has effectively catalyzed various organic transformations, 6,7 direct catalytic asymmetric aldol, 8 Mannish, 9 Michael, 10 Diels–Alder, 11 α-amination reaction, 12 Knoevenagel-type condensation, 13 Biginelli reaction, 14 and asymmetric Hantzsch reaction. 15…”

A Three-Component Synthesis of N-Substituted Quinoline- 3-Carbonitrile Derivatives Catalysed by L-Proline

“…9 Recently, many small organic molecules, for instance cinchona alkaloids and l-proline and its derivatives have been used in various organic reactions to give excellent yields. Amongst these enamine-based direct catalytic asymmetric aldol, 10,11 Mannich, 12,13 Michael, 14,15 Diels-Alder, 16,17 a-amination reactions, and Knoevenagel type reactions 16,17,18 using l-proline as catalyst have been reported. More recently, l-proline and its derivatives have been used in multi-component unsymmetric Biginelli 19,20 and Hantzsch reactions.…”