Configuration Sampling With Five‐Membered AtropisomericP,N‐Ligands

Abstract

Here we report a strategy for the systematic variation of atropisomeric C 1 -symmetric P,N ligands to incrementally change the position of the groups within the chiral pocket without modifying their steric parameters. More specifically, the effects of systematic modification of the nitrogen heterocycle in atropisomeric C 1 -symmetric stack ligands have been investigated in this study. The versatility and applicability of this approach has been demonstrated in mechanistically distinct catalytic enantioselective transformations, resulting in the identification of a P,N-ligand for a highly enantioselective synthesis of organoboranes.

anti-Selective synthesis of β-boryl-α-amino acid derivatives by Cu-catalysed borylamination of α,β-unsaturated esters

“…Although the related copper-catalysed boron conjugate addition of α,β-unsaturated carbonyls was well studied, 12 the tandem α-functionalisation of the copper enolate intermediate still remains underdeveloped, except for the classical aldol-type processes. 13 …”

Tuning StackPhim Ligands: Applications in Enantioselective Borylation and Alkynylation

“…As a complement to this approach, we recently reported a 'configuration sampling' strategy demonstrating that the position of the pendant group on the five-membered heterocycle is of utmost importance in achieving high enantioselectivity in a conjugate boron addition reaction (Scheme 1b). 20 A variety of different ligand types such as bisphosphines (Josiphos, 21,22 Qui-noxP*, 23 Taniaphos), 24 NHCs, 25,26 and other planar chiral ligands 27,28 are effective here, but other P,N-ligands have been met with limited success. Our interest in this reaction is primarily to push the boundaries of the P,N-ligand class with our ligand design.…”

“…Compounds 4a-4e; General Procedure for Enantioselective -Borylation 20 Inside an argon-filled glovebox, CuCl (0.60 mg, 0.006 mmol, 5 mol%) was added to a 5-mL oven-dried round-bottom flask charged with a magnetic stir bar before the flask was sealed with a rubber septum and removed from the glovebox. Stack ligand (0.007 mmol, 5.5 mol%) and solvent (0.5 mL) were added, and the mixture was stirred for 15-20 min at rt to observe a transparent yellow solution of catalyst.…”

Selective Electroreductive Hydroboration of Olefins with B2pin2

“…In recent decades, due to the efficient functionalization capability of olefins, the hydroboration reactions represent a promising strategy to construct valuable organoboron compounds . Especially the catalytic hydroboration of alkenes using B 2 pin 2 reagent represents a high functional-group tolerance method to an expedient access of substituted alkylboron compounds. , Despite significant progress have been made in this field, hydroboration protocols of olefins still have such limitations: (a) unsatisfactory regioselectivity, (b) toxic loading of noble metals, (c) harsh reaction conditions, and (d) the use of stoichiometric amounts of reducing reagents. Therefore, the development of a green strategy for olefin hydroboration is still highly desirable.…”