Catalytic Diastereo- and Enantioconvergent Synthesis of Vicinal Diamines from Diols through Borrowing Hydrogen.

We present herein an unprecedented diastereoconvergent synthesis of vicinal diamines from diols through an economical, redox-neutral process. Under cooperative ruthenium and Lewis acid catalysis, readily available anilines and 1,2-diols (as a mixture of diastereomers) couple to forge two C-N bonds in an efficient and diastereoselective fashion. By identifying an effective chiral iridium/phosphoric acid co-catalyzed procedure, the first enantioconvergent double amination of racemic 1,2-diols has also been achieved, resulting in a practical access to highly valuable enantioenriched vicinal diamines.

Desymmetrization of 1,3-Diones by Catalytic Enantioselective Condensation with Hydrazine.

We present herein an unprecedented desymmetrization of meso 1,3-diones by enantioselective intermolecular condensation. Under the catalysis by a chiral phosphoric acid, a range of readily available 1,3-diones undergo reaction with hydrazines to produce cyclic and acyclic keto-hydrazones bearing an all-carbon quaternary center in high efficiency and enantioselectivity. These compounds are also highly versatile for the preparation of multifunctional building blocks and heterocycles in excellent stereoselectivity.

Room-Temperature Guerbet Reaction with Unprecedented Catalytic Efficiency and Enantioselectivity.

We report herein an unprecedented highly efficient Guerbet-type reaction at room temperature (catalytic TON up to >6000). This ß-alkylation of secondary methyl carbinols with primary alcohols has significant advantage of delivering higher-order secondary alcohols in an economical, redox-neutral fashion. In addition, the first enantioselective Guerbet reaction has also been achieved using a commercially available chiral ruthenium complex to deliver secondary alcohols with moderate yield and up to 92 % ee. In both reactions, the use of a traceless ketone promoter proved to be beneficial for the catalytic efficiency.

Rhodium-Catalyzed Enantioconvergent Isomerization of Homoallylic and Bishomoallylic Secondary Alcohols.

We present herein an unprecedented enantioselective isomerization of homoallylic and bishomoallylic secondary alcohols, catalyzed by a commercially available rhodium-complex and a base. This catalytic redox-neutral process provides an effective access to chiral ketones in high efficiency and enantioselectivity, without the use of any stoichiometric reagent or generation of any waste. For the reaction of homoallylic alcohols, this system achieved not only a stereoconvergent access to chiral ketones bearing a ß-stereocenter (up to 95%, 86% ee) but also a concomitant oxidative kinetic resolution of the alcohol substrates (S > 20). In the case of bishomoallylic alcohols, an intriguing ligand-induced divergent reactivity was observed. A terminal-to-internal alkene isomerization promoted by Rh/L7 followed by redox isomerization using Rh/BINAP system produced chiral ketones bearing a γ-stereocenter with high yield and enantioselectivity. Mechanistic studies provided strong support for the redox-isomerization pathway with chain walking of the key alkyl-Rh intermediate.