Copper‐Catalyzed Borylative Cross‐Coupling of Allenes and Imines: Selective Three‐Component Assembly of Branched Homoallyl Amines

Abstract

A copper‐catalyzed three‐component coupling of allenes, bis(pinacolato)diboron, and imines allows regio‐, chemo‐, and diastereoselective assembly of branched α,β‐substituted‐γ‐boryl homoallylic amines, that is, products bearing versatile amino, alkenyl, and borane functionality. Alternatively, convenient oxidative workup allows access to α‐substituted‐β‐amino ketones. A computational study has been used to probe the stereochemical course of the cross‐coupling.

Asymmetric Synthesis of Secondary and Tertiary Boronic Esters

“…[158] Tortosa has also used this reactivity platform for the aminoboration of cyclopropenes. [59] Borylated alkyl-copper species have also been trapped with aldehydes and ketones, [159] imines, [160][161][162] Michael acceptors, [163] and allylic electrophiles, [164] although both the nature of the substrate p-system (allenes and terminal dienes as opposed to internal or activated alkenes) and the regioselectivity of the initial insertion means that secondary alkyl boronic esters are not accessed.…”

Asymmetrische Synthese sekundärer und tertiärer Boronsäureester

“…Tortosa nutzte diese Reaktivitätsplattform außerdem fürd ie Aminoborierung von Cyclopropenen. [59] Borylierte Kupferalkylspezies wurden auch mit Aldehyden und Ketonen, [159] Iminen, [160][161][162] Michael-Akzeptoren [163] und Allylelektrophilen [164] abgefangen, allerdings resultiert aus der Art des p-Systems des Substrats (Allene und terminale Diene im Gegensatz zu internen oder aktivierten Alkenen) sowie auch aus der Regioselektivitätd er anfänglichen Insertion, dass keine sekundären Alkylboronsäureester zugänglich sind.…”

Enantio‐ and Diastereoselective Synthesis of Homopropargyl Amines by Copper‐Catalyzed Coupling of Imines, 1,3‐Enynes, and Diborons

“…We and others have described efficient routes to amines through the multicomponent coupling of imines with hydrocarbon pro-nucleophiles and boron reagents. [8][9][10] Krische pioneered the use of enynes as hydrocarbon pro-nucleophiles in transition metal-catalyzed transformations, [11][12][13] however, in both reductive and borylative coupling, the asymmetric union of imines and enynes remains an unmet challenge. [14] We envisaged a new approach to homopropargyl amines involving the copper-catalyzed enantio-and diastereoselective multicomponent coupling of imines, enynes, and diboron reagents (Scheme 1 C).…”