Iridium‐Catalyzed Asymmetric Hydrogenation of 2,3‐Diarylallyl Amines with a Threonine‐Derived P‐Stereogenic Ligand for the Synthesis of Tetrahydroquinolines and Tetrahydroisoquinolines

Chiral compounds containing nitrogen heteroatoms are fundamental substances for the chemical, pharmaceutical and agrochemical industries. However, the preparation of some of these interesting scaffolds is still underdeveloped. Herein we present the synthesis of a family of P‐stereogenic phosphinooxazoline iridium catalysts from L‐threonine methyl ester and their use in the asymmetric hydrogenation of N‐Boc‐2,3‐diarylallyl amines, achieving very high enantioselectivity. Furthermore, the synthetic utility of the 2,3‐diarylpropyl amines obtained is demonstrated by their transformation to 3‐aryl‐tetrahydroquinolines and 4‐benzyl‐tetrahydroisoquinolines, which have not yet been obtained in an enantioselective manner by direct reduction of the corresponding aromatic heterocycles. This strategy allows the preparation of these types of alkaloids with the highest enantioselectivity reported up to date.

Regio- and Stereoselective 1,2-Carboboration of Ynamides with Aryldichloroboranes

Catalyst‐free 1,2‐carboboration of ynamides is presented. Readily available aryldichloroboranes react with alkyl‐ or aryl‐substituted ynamides in high yields with complete regio‐ and stereoselectivity to valuable β‐boryl‐β‐alkyl/aryl α‐aryl substituted enamides which belong to the class of trisubstituted alkenylboronates. The 1,2‐carboboration reaction is experimentally easy to conduct, shows high functional group tolerance and broad substrate scope. Gram‐scale reactions and diverse synthetic transformations convincingly demonstrate the synthetic potential of this method. The reaction can also be used to access 1‐boraphenalenes, a class of boron‐doped polycyclic aromatic hydrocarbons.

C-Boron Enolates Enable Palladium Catalyzed Carboboration of Internal 1,3-Enynes

A new family of carbon-bound boron enolates, generated by a kinetically controlled halogen exchange between chlorocatecholborane and silylketene acetals, is described. These C-boron enolates are demonstrated to activate 1,3-enyne substrates in the presence of a Pd⁰ /Senphos ligand complex, resulting in the first examples of a carboboration reaction of an alkyne with enolate-equivalent nucleophiles. Highly substituted dienyl boron building blocks are produced in excellent site-, regio-, and diastereoselectivity by the described catalytic cis-carboboration reaction.

Brønsted Acid Enabled Nickel-Catalyzed Hydroalkenylation of Aldehydes with Styrene and its Derivatives

A Brønsted acid enabled nickel-catalyzed hydroalkenylation of aldehydes and styrene derivatives has been developed. The Brønsted acid acts as a proton shuttle to transfer a proton from the alkene to the aldehyde, thereby leading to an economical and byproduct-free coupling. A series of synthetically useful allylic alcohols were obtained through one-step reactions from readily available styrene derivatives and aliphatic aldehydes in up to 88 % yield and with high linear selectivity.