Cu-Catalyzed Asymmetric Hydroboration of Naphthylallylic Compounds for Enantioselective Synthesis of Chiral Boronates

Abstract

A Cu-catalyzed regio- and enantioselective hydroboration of various naphthylallylic compounds affording chiral boronates with high yields and excellent enantioselectivities (up to 96% ee) was presented. The utility of the boronated products is further illustrated by other stereospecific C–B bond transformations to produce amino alcohols and other useful compounds.

Simplified Synthesis of Air-stable Copper-complexed Josiphos Ligand via Ugi’s Amine: Complete Preparation and Analysis from Ferrocene

“…3 The resulting acetate was then subjected to a substitution reaction with dimethylamine in methanol. Trace amounts of Ugi's amine (1) were isolated; however, the major product formed was 1-ferrocenyl ethyl methyl ether (5). In attempt to avoid the formation of the unwanted ether, an alternate acetylation/amination step was performed in a one-pot fashion (Table 1).…”

“…2 Josiphos-type ligands are widely used across different reaction types, including asymmetric allylation, 3 hydrosilylation, 4 and hydroboration(Scheme 1a). 5 The chiral building block that is used as starting material for Josiphos-type ligands is [1-(dimethylamino)ethyl]ferrocene ((R)-1), also known as Ugi's amine. Starting from enantiopure Ugi's amine, a wide range of ligands can be achieved in two steps, through directed lithiation of the cyclopentadienide ring and a substitution of the amine group that proceeds via an SN1-type mechanism (Scheme 1b).…”

Simplified Synthesis of an Air-Stable Copper-Complexed Josiphos Ligand via Ugi’s Amine: Complete Preparation and Analysis from Ferrocene

“…2 Josiphos-type ligands are widely used across different reaction types, including asymmetric allylation, 3 hydrosilylation, 4 and hydroboration (Scheme 1a ). 5…”

“…3 The resulting acetate was then subjected to a substitution reaction with dimethylamine in methanol. Trace amounts of Ugi's amine (1) were isolated; however, the major product formed was 1-ferrocenyl ethyl methyl ether (5).…”

Highly diastereo- and enantioselective copper-catalyzed methylboration of 1,2-dihydroquinolines and 2H-chromenes

“…Ito and co-workers reported the asymmetric dearomative methylboration of indole with good diastereoselectivity catalysed by the copper complex of chiral carbene, but only 22% ee was obtained. 17 Based on prior efforts and the significance of heterocyclic compounds in pharmaceuticals, 18 we attempt to develop a highly diastereo- and enantioselective Cu-catalyzed methylboration of diverse heterocyclic compounds including 1,2-dihydroquinolines, 2 H -chromenes and 2 H -thiochromenes for the synthesis of multichiral boryl heterocyclic compounds and their derivatives. Herein, we wish to report the first copper-catalyzed methylboration of 1,2-dihydroquinolines and 2 H -chromenes to realize the construction of two adjacent chiral centers, providing the corresponding multichiral boryl heterocyclic compounds and their derivatives bearing two adjacent chiral centers with excellent diastereo- and enantioselectivities (dr >99 : 1 and ee up to 99.9%) (Scheme 1).…”