Mizoroki−Heck Type Reaction of Organoboron Reagents with Alkenes and Alkynes. A Pd(II)-Catalyzed Pathway with Cu(OAc)₂ as an Oxidant

Abstract

[reaction: see text]. In contrast to the Pd(0)-catalyzed mechanism by Uemura, Mizoroki-Heck type reaction of boronic acids is found to proceed under a Pd(II)-mediated pathway using a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 as an oxidant. Treatment of a variety of alkenes with boronic acids, boronates, and sodium tetraphenylborate furnishes beta-arylated and alkenylated products in good to excellent yields. The reactions with norbornene, norbornadiene, and diphenylacetylene are also performed to give 1:2 or 2:1 coupling products.

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

“…[14] This chemistry has dramatically expanded the utility of organoboron compounds in synthetic and medicinal chemistry, and in the synthesis of new organic materials. In addition to many applications and new improvements in the Pd-catalyzed Suzuki coupling, [4,5,[15][16][17] several additional metal-catalyzed processes involving organoboron compounds were also developed in recent years, including: the Heck-type Pd-catalyzed cross-coupling with alkenes, [18,19] the Rhcatalyzed 1,2 addition to aldehydes or imines and 1,4 addition to unsaturated carbonyl compounds, [4,20] the Rh-catalyzed addition to alkenes or alkynes, [20] the Ni-catalyzed coupling with alkynes and imines, [21] the Cu-catalyzed cross-coupling forming C-O and C-N bonds, [22] the Pd/Cu catalyzed cross-coupling with thioesters, [23] and various metal-catalyzed methods for the C-H borylation and further transformation of aromatic compounds. [24][25][26] …”

Highly Efficient and Reusable Polyaniline‐Supported Palladium Catalysts for Open‐Air Oxidative Heck Reactions under Base‐ and Ligand‐Free Conditions

“…[1][2][3][4][5] This is mainly because of the large diversity of readily accessible arylboronic acids, their moistureand air-stability, low toxicity and easy removal of the boron-derived by-products coupled with the high chemo-and regioselectivity of the reaction. The oxidative Heck reaction was first discovered by Heck using a stoichiometric amount of palladium salts [1] and subsequently its catalytic version was developed by Uemura, [2] Mori [3] and Jung et al [4] using palladium salts in presence of a co-oxidant.…”

“…[1][2][3][4][5] This is mainly because of the large diversity of readily accessible arylboronic acids, their moistureand air-stability, low toxicity and easy removal of the boron-derived by-products coupled with the high chemo-and regioselectivity of the reaction. The oxidative Heck reaction was first discovered by Heck using a stoichiometric amount of palladium salts [1] and subsequently its catalytic version was developed by Uemura, [2] Mori [3] and Jung et al [4] using palladium salts in presence of a co-oxidant. Usually a metal salt such as CuA C H T U N G T R E N N U N G (OAc) 2 [3,4a] or molecular oxygen [4] are used as co-oxidants to reoxidize Pd(0) in the OH reactions which in turn generates a stoichiometric amount of metal waste or cause problems associated with the use of handling pure oxygen gas, reducing the utility of the procedure for large-scale applications.…”

Ligand-free Palladium-Catalyzed Mizoroki-Heck-type Reaction of Arylboronic Acids and Alkenes Using Silver Cation

“…Silver cations then oxidized the Pd (0) to Pd(II) species. 19 In addition, no Michael-type addition product was obtained in the presence of silver cations, despite the addition of the proton source reagent, such as iPrOH and water, in the reaction mixture (Table 1, entries [15][16][17]. When PPh3 was employed as a ligand in this catalytic system, it promoted the homocoupled byproduct (Table 1, entry 11).…”