Diastereoselective Iridium-Catalyzed Amination of Biosourced Isohexides Through Borrowing Hydrogen Methodology

Ir-Catalyzed Synthesis of Functionalized Pyrrolidines and Piperidines Using the Borrowing Hydrogen Methodology

The Ir(III)-catalyzed synthesis of 3-pyrrolidinols and 4-piperidinols combining 1,2,4-butanetriol or 1,3,5-pentanetriol with primary amines was carried out. This borrowing hydrogen methodology was further extended to the sequential diamination of triols leading to amino-pyrrolidines and amino-piperidines.

1,4-d-Sorbitan: A Promising Biobased-Platform for the Synthesis of Chiral Amines

The regio- and diastereoselective synthesis of chiral amines derived from 1,4-d-sorbitan has been developed via the borrowing hydrogen reaction using a cooperative catalysis between an achiral iridium catalyst and diphenylphosphoric acid. The different reactivities of the four hydroxyl groups on the 1,4-d-sorbitan scaffold have also been highlighted.

Synthesis of Chiral Amines via Asymmetric Hydrogen Borrowing

Chiral amines have been widely used in pharmaceutical, agrochemical and fine-chemical industries. With water as the only byproduct and requiring no extra reducing reagent, the reaction of alcohols with amines via a ‘hydrogen borrowing’ pathway is a green route to prepare chiral amines. This paper gives a brief summary of progress on asymmetric amination of alcohols to produce chiral amines via the ‘hydrogen borrowing’ strategy.

Control of Absolute Stereochemistry in Transition-Metal-Catalysed Hydrogen-Borrowing Reactions

Hydrogen-borrowing catalysis represents a powerful method for the alkylation of amine or enolate nucleophiles with non-activated alcohols. This approach relies upon a catalyst that can mediate a strategic series of redox events, enabling the formation of C-C and C-N bonds and producing water as the sole by-product. In the majority of cases these reactions have been employed to target achiral or racemic products. In contrast, the focus of this Minireview is upon hydrogen-borrowing-catalysed reactions in which the absolute stereochemical outcome of the process can be controlled. Asymmetric hydrogen-borrowing catalysis is rapidly emerging as a powerful approach for the synthesis of enantioenriched amine and carbonyl containing products and examples involving both C-N and C-C bond formation are presented. A variety of different approaches are discussed including use of chiral auxiliaries, asymmetric catalysis and enantiospecific processes.

Transition-Metal-Free Hydrogen Autotransfer: Diastereoselective N-Alkylation of Amines with Racemic Alcohols

A practical method for the synthesis of α-chiral amines by alkylation of amines with alcohols in the absence of any transition-metal catalysts has been developed. Under the co-catalysis of a ketone and NaOH, racemic secondary alcohols reacted with Ellman's chiral tert-butanesulfinamide by a hydrogen autotransfer process to afford chiral amines with high diastereoselectivities (up to >99:1). Broad substrate scope and up to a 10 gram scale production of chiral amines were demonstrated. The method was applied to the synthesis of chiral deuterium-labelled amines with high deuterium incorporation and optical purity, including examples of chiral deuterated drugs. The configuration of amine products is found to be determined solely by the configuration of the chiral tert-butanesulfinamide regardless of that of alcohols, and this is corroborated by DFT calculations. Further mechanistic studies showed that the reaction is initiated by the ketone catalyst and involves a transition state similar to that proposed for the Meerwein-Ponndorf-Verley (MPV) reduction, and importantly, it is the interaction of the sodium cation of the base with both the nitrogen and oxygen atoms of the sulfinamide moiety that makes feasible, and determines the diastereoselectivity of, the reaction.