Pd/PC‐Phos‐Catalyzed Enantioselective Intermolecular Denitrogenative Cyclization of Benzotriazoles with Allenes and N‐Allenamides

Reported herein is an asymmetric Pd/PC‐Phos‐catalyzed denitrogenative cyclization of benzotriazoles with allenes and N‐allenamides, representing the first example of enantioselective denitrogenative cyclizations of benzotriazoles. A series of optically active 3‐methyleneindolines were obtained in good yields with high ee values. The use of inexpensive and readily available starting materials, high regio‐ and enantioselectivity, a broad substrate scope, mild reaction conditions, no need for base, as well as versatile functionalization of the 3‐methyleneindolines make this approach attractive.     

One‐Pot N‐Deprotection and Catalytic Intramolecular Asymmetric Reductive Amination for the Synthesis of Tetrahydroisoquinolines

A one‐pot N‐Boc deprotection and catalytic intramolecular reductive amination protocol for the preparation of enantiomerically pure tetrahydroisoquinoline alkaloids is described. The iodine‐bridged dimeric iridium complexes displayed superb stereoselectivity to give tetrahydroisoquinolines, including several key pharmaceutical drug intermediates, in excellent yields under mild reaction conditions. Three additives played important roles in this reaction: Titanium(IV) isopropoxide and molecular iodine accelerated the transformation of the intermediate imine to the tetrahydroisoquinoline product; p ‐toluenesulfonic acid contributed to the stereocontrol.     

Rhodium(I)‐Catalyzed Enantioselective Cyclization of Enynes by Intramolecular Cleavage of the Rh−C Bond by a Tethered Hydroxy Group

Rhodium(I)‐catalyzed enantioselective intramolecular cyclization of enynes having a hydroxy group in the tether was investigated, and various cyclic compounds possessing a chiral quaternary carbon center were obtained in high yields with high ees. In this cyclization, a Rh?C(sp²) bond in the rhodacyclopentene intermediate, which was formed by enantioselective oxidative cycloaddition of enynes to a chiral rhodium(I) complex, was intramolecularly cleaved by σ‐bond metathesis of a tethered O?H bond in the substrate. Furthermore, it was found that the cyclic compounds were obtained with high ees even when the starting materials having a racemic secondary alcohol moiety were used in this reaction.     

Enantioselective Rhodium‐Catalyzed Addition of Arylboroxines to N‐Unprotected Ketimines: Efficient Synthesis of Cipargamin

Highly enantioselective rhodium‐catalyzed addition of arylboroxines to N‐unprotected ketimines is realized for the first time by employing chiral BIBOP‐type ligands with a Rh loading as low as 1 mol %. A range of chiral α‐trifluoromethyl‐α,α‐diaryl α‐tertiary amines or 3‐amino‐3‐aryloxindoles were formed with excellent ee values and yields by employing either WingPhos or PFBO‐BIBOP as the ligand. The method has enabled an efficient enantioselective synthesis of cipargamin.     

Asymmetric Synthesis of α,α‐Disubstituted Allylic Amines through Palladium‐Catalyzed Allylic Substitution

The first asymmetric synthesis of important α,α‐disubstituted N‐alkyl allyl amine scaffolds through allylic substitution is reported. This approach is based on palladium catalysis and features ample scope with respect to both the allylic precursor and amine reagent, and high asymmetric induction with enantiomeric ratios (e.r.) up to 98.5:1.5. The use of less‐reactive anilines is also feasible, providing enantioenriched α,α‐disubstituted N‐aryl allylic amines.