Visible-Light-Driven Decarboxylative Borylation: Rapid Access to α- and ß-Amino-boronamides.

In this study, we described a two-step process involving an efficient visible-light-induced decarboxylative borylation of α- and ß-amino redox-active esters with bis(catecholato)diboron, followed by transamination with 1,8-diaminonapthalene (DANH2). A series of boronamides were obtained in moderate to excellent yields in this one-pot procedure. The photochemical process proved to be very efficient even when conducted under flow conditions with shorter reaction durations and scalable synthesis of DAN boronates.

Synthesis of Enantioenriched ß-Hydroxy-γ-Acetal Enamides by Rhodium-Catalyzed Asymmetric Transfer Hydrogenation.

The asymmetric reduction of ß-keto-γ-acetal enamides has been investigated. A wide range of enantioenriched ß-hydroxy-γ-acetal enamides were obtained through asymmetric transfer hydrogenation catalyzed by a tethered Rh(III)-DPEN complex with yields up to quantitative and enantioselectivities up to 99%. The reaction proved to be highly chemoselective toward the reduction of the carbonyl group over the C═C bond.

Synthesis of Highly Substituted Azepanones from 2 H-Azirines by a Stepwise Annulation/Ring-Opening Sequence.

Bicyclic aziridines possessing a 1-azabicyclo[4.1.0]heptan-2-one core were prepared from 2 H-azirines by a stepwise annulation sequence involving a diastereoselective allylindanation, an N-acylation, and a ring-closing metathesis to construct the six-membered ring. After hydrogenation or functionalization of the olefin, regioselective ring opening of the resulting azabicyclic compounds with carboxylic acids (or sulfur nucleophiles) afforded highly substituted azepanones possessing an ester moiety or a trifluoromethyl group and a tetrasubstituted carbon at the α and ß positions of the nitrogen atom, respectively.

Enantioselective Synthesis of α-Acetal-ß'-Amino Ketone Derivatives by Rhodium-Catalyzed Asymmetric Hydrogenation.

A range of ß-keto-γ-acetal enamides has been synthesized and transformed into the corresponding enantioenriched α-acetal-ß'-amino ketones with enantioinductions of up to 99% by using rhodium/QuinoxP*-catalyzed enantioselective hydrogenation under mild conditions. This method also proved to be highly chemoselective toward the reduction of the C-C double bond.

Asymmetric Transfer Hydrogenation of (Hetero)arylketones with Tethered Rh(III)-N-(p-Tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine Complexes: Scope and Limitations.

A series of new tethered Rh(III)/Cp* complexes containing the N-(p-tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine ligand have been prepared, characterized, and evaluated in the asymmetric transfer hydrogenation (ATH) of a wide range of (hetero)aryl ketones. The reaction was performed under mild conditions with the formic acid/triethylamine (5:2) system as the hydrogen source and provided enantiomerically enriched alcohols with good yields and high to excellent enantioselectivities. Although the nature of the substituents on the phenyl tethering ring did not alter the stereochemical outcome of the reaction, complexes bearing electron-donating groups exhibited a higher catalytic activity than those having electron-withdrawing groups. A scale-up of the ATH of 4-chromanone to the gram scale quantitatively delivered the reduced product with excellent enantioselectivity, demonstrating the potential usefulness of these new complexes.

Mild nonepimerizing N-alkylation of amines by alcohols without transition metals.

A one-pot two-step sequence involving an oxidation/imine-iminium formation/reduction allowed the N-alkylation of amines by alcohols without any epimerization when optically active alcohols and amines are involved in the process.