Pyrrolidine and Indolizidine Alkaloids from Chiral N-tert-Butanesulfinyl Imines Derived from 4-Halobutanal

An efficient stereocontrolled preparation of 2-substituted pyrrolidines and 5-substituted indolizidin-7-ones, by using chiral N-tert-butanesulfinyl imines derived from 4-halobutanal as starting materials, is detailed. Addition of Grignard reagents and a decarboxylative Mannich­ reaction with β-keto acids involving these chiral imines proceeded with high diastereoselectivity. The synthesis of the pyrrolidinic alkaloids (–)-bgugaine, (+)-villatamine B, (–)-norhygrine, trans-dendrochrysanine, and (–)-ruspolinone demonstrated the utility of this methodology.

Enantiodivergent Aldol Condensation in the Presence of Aziridine/Acid/Water Systems

A series of novel chiral imines was synthesized from corresponding aldehydes and 1-(2-aminoalkyl)aziridines with good chemical yields. Such imines were tested as catalysts in the direct asymmetric aldol reaction between aromatic aldehydes and acetone/cyclohexanone in the presence of catalytic amounts of water and an acidic additive. The corresponding aldol products were formed in excellent yields and with very high enantioselectivities (98% and 99% ee, respectively).

Electronic effects in tautomeric equilibria: the case of chiral imines from d-glucamine and 2-hydroxyacetophenones

Hammett plots show straightforward relationships for tautomeric equilibria in a new class of chiral imine–enamine structures.

Induced chirality sensing through formation and aggregation of the chiral imines double winged with pyrenes or perylenes

Aggregation-amplified circular dichroism led to efficient and convenient chirality sensing.

Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins

New pyrrolidine-based organocatalysts with a bulky substituent at C2 were synthesized from chiral imines derived from (R)-glyceraldehyde acetonide by diastereoselective allylation followed by a sequential hydrozirconation/iodination reaction. The new compounds were found to be effective organocatalysts for the Michael addition of aldehydes to nitroolefins and enantioselectivities up to 85% ee were achieved.