Mandelamide−Zinc-Catalyzed Enantioselective Alkyne Addition to Heteroaromatic Aldehydes

Bimetallic zinc complex – active species in coupling of terminal alkynes with aldehydes via nucleophilic addition/Oppenauer oxidation

A mechanistic study on the zinc-promoted coupling between aldehydes and terminal alkynes was demonstrated. A bimetallic zinc complex was determined to be the active species.

Zinc-mediated addition of diethyl bromomalonate to alkynes for the cascade reaction towards polysubstituted pyranones and tetracarbonyl derivatives

The zinc-mediated regioselective addition reactions of diethyl bromomalonate and aromatic and aliphatic alkynes were investigated for the synthesis of vinyl malonates. When the vinyl organo-zinc intermediates were reacted with acid chlorides 2H-pyran-2-ones were obtained while the application of oxalyl chloride and an amine led to tetracarbonyl derivatives in a one-pot multi-step reaction sequence.

Enantioselective synthesis of α-oxy amides via Umpolung amide synthesis

α-Oxy amides are prepared through enantioselective synthesis using a sequence beginning with a Henry addition of bromonitromethane to aldehydes and finishing with Umpolung Amide Synthesis (UmAS). Key to high enantioselection is the finding that ortho-iodo benzoic acid salts of the chiral copper(II) bis(oxazoline) catalyst deliver both diastereomers of the Henry adduct with high enantiomeric excess, homochiral at the oxygen-bearing carbon. Overall, this approach to α-oxy amides provides an innovative complement to alternatives that focus almost entirely on the enantioselective synthesis of α-oxy carboxylic acids.

Dimethylzinc-Mediated, Enantioselective Synthesis of Propargylic Amines

A one-pot, enantioselective synthesis of N-aryl propargylic amines, using alkynylation reagents obtained from dimethylzinc and terminal acetylenes in combination with various aldehydes and o-methoxyaniline as starting materials, has been developed. Enantiopure beta-amino alcohols derived from norephedrine were used as non-covalent chiral auxiliaries, both in stoichiometric or substoichiometric amount. After optimization, propargylic amines were obtained in good to high yields (up to 93%) and with moderate to high enantiomeric excesses (up to 97% ee). The possibility to recover the chiral auxiliary after the reaction was demonstrated.

Asymmetric addition of 1-ethynylcyclohexene to both aromatic and heteroaromatic ketones catalyzed by a chiral Schiff base-zinc complex

The evaluation of a chiral Schiff base ligand in the zinc-catalyzed asymmetric addition of 1-ethynylcyclohexene to both aromatic and heteroaromatic ketones is reported (with up to 83% enantioselectivity and up to 88% isolated yield).