Simple Ionic Liquid Supported C₂‐Symmetric Bisprolinamides as Recoverable Organocatalysts for the Asymmetric Aldol Reaction in the Presence of Water

Abstract

C2‐Symmetric (S)‐prolinamides modified with ionic groups and bearing achiral diamine units were synthesized. Their potency as reusable organocatalysts for asymmetric aldol reactions of cycloalkanones or methyl ketones with aromatic (heteroaromatic) aldehydes in the presence of water was demonstrated. The 1,4‐diaminobenzene‐derived catalyst exhibited good catalytic performance and excellent recoverability over at least 15 reaction–regeneration cycles under the studied conditions.

Ionic Liquid Immobilized Organocatalysts for Asymmetric Reactions in Aqueous Media

“…Later, the same research group designed and synthesized a series of ionic liquid immobilized C 2 -symmetric amides of (S)-proline bearing achiral diamine units 16 ( Figure 3) to carry out asymmetric aldol reactions in water [58]. High enantioselectivities and yields were observed for a large variety of cyclic and acyclic ketones as donors and aromatic (heteroaromatic) aldehydes as acceptors.…”

Greener synthetic approach for the preparation of substituted flexible dimeric pyridinium salts and its importance

“…Simple ionic liquid supported C 2‐symmetric bisprolinamides are used as recoverable organo catalysts for the asymmetric aldol reaction [7]. Imidazopyridine derivatives are important kind of N ‐heterocycles and exhibit diverse biological, pharmaceutical, anticancer, antiviral, antiparasitic, anti‐HIV properties, and catalytic responses [8,9].…”

A Snapshot of Ionic-Liquid-Tagged Proline-Based Organocatalysts

“…Since that initial work, there have been several reports of this class of catalyst, although major contributions to this field have emerged primarily from the groups of Zlotin, [15,[18][19][20][21][22] Lombardo, [23,24] and Liebscher. [14,25,26] Organocatalyst 3 ( Fig.…”

“…[29][30][31][32][33] In that study, a 10 mol-% catalyst loading in the presence of water (100 equivalents with respect to the aldehyde) furnished aldol products in excellent enantioselectivity and very high yield (96 % ee, 95 : 5 anti : syn, 99 % yield). [21] The proposed role of water in the emulsion was to reinforce important hydrophobic effects which enhance stereoselectivity within the transition state, although removal of water from the reaction mixture had a minor influence on the diastereomeric ratio (dr) (89 : 11 anti : syn) only. Despite this inconsistency, under the optimal conditions 8 was a suitable catalyst for cyclic ketones paired with activated aldehydes although it did not perform well when employing electron rich aldehydes as the electrophile, or when any aldehyde was employed as the nucleophile.…”

“…2) is the most structurally complex IL-tagged catalyst to date [21] and draws on recent catalyst design strategies to develop scaffolds which bear more than one 'catalytic unit'. [29][30][31][32][33] In that study, a 10 mol-% catalyst loading in the presence of water (100 equivalents with respect to the aldehyde) furnished aldol products in excellent enantioselectivity and very high yield (96 % ee, 95 : 5 anti : syn, 99 % yield).…”