Catalytic Boracarboxylation of Alkynes with Diborane and Carbon Dioxide by an N-Heterocyclic Carbene Copper Catalyst

Abstract

By the use of an N-heterocyclic carbene copper(I) complex as a catalyst, the boracarboxylation of various alkynes (e.g., diaryl alkynes, aryl/alkyl alkynes, and phenylacetylene) with a diborane compound and carbon dioxide has been achieved for the first time, affording the α,β-unsaturated β-boralactone derivatives regio- and stereoselectively via a borylcupration/carboxylation cascade. Some important reaction intermediates were isolated and structurally characterized to clarify the reaction mechanism.

Transition Metal-catalyzed Fixation of Carbon Dioxide <i>via</i> Carbon–carbon Bond Formation

“…Previously, boracarboxylation of alkynes was achieved using Cu catalysts and bis(pinacolato)diboron as the boron source 62) . We reported the first catalytic silacarboxylation of internal alkynes employing CO2 and silylborane in the presence of a Cu catalyst (Scheme 20) 63) .…”

Using sustainable metals to carry out “green” transformations: Fe- and Cu-catalyzed CO2 monetization

“…Very recently, the unprecedented silacarboxylation of internal alkynes with CO 2 and silylboranes, catalyzed by various phosphine-and NHC-substituted copper complexes was investigated by Tsuji and co-workers [57]. A series of copper complexes formed in situ from CuCl and phosphine ligands ( In another report, Hou and co-workers [59] Cyclic carbonates are another family of useful heterocyclic compounds that can be obtained through copper-catalyzed CO 2 monetization transformations [25,67]. In 1961, Dimroth, Pasedach, and Schneider performed the cyclization reaction between tertiary acetylenic alcohols and carbon dioxide under pressure to form the corresponding substituted cyclic carbonates (Scheme 23) [68][69].…”

Catalytic conversion of carbon dioxide to carboxylic acid derivatives

“…A boracarboxylation protocol of various alkynes with a diborane reagent has been achieved for the fi rst time by using an (IMes)CuCl complex as the catalyst, aff ording α,β -unsaturated-β -boralactone derivatives. 61 Th e reaction proceeds via a borylcupration-carboxylation Hydrocarboxylation is another effi cient method to obtain linear acrylic acid from alkynes, and the copper-fl uoride-bearing N-heterocyclic carbene ligand is found to suffi ciently catalyze such transformation in the presence of a hydrosilane as reducing reagent. 59 Internal alkynes could be transformed in high regioselectivities to give cis -acrylate product under mild reaction conditions without rigorous evacuation of air and moisture as illustrated in Scheme 10 .…”