Copper‐Catalyzed Oxyboration of Unactivated Alkenes

Abstract

The first regiodivergent oxyboration of unactivated terminal alkenes is reported, using copper alkoxide as a catalyst, bis(pinacolato)diboron [(Bpin)2 ] as a boron source, and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as an oxygen source. The reaction is compatible with various functional groups. Two regioisomers are selectively produced by selecting the appropriate ligands on copper. The products may be used as a linchpin precursor for various other functionalizations, and net processes such as carbooxygenation, aminooxygenation, and dioxygenation of alkenes can be achieved after C-B bond transformations. Mechanistic studies indicate that the reaction involves the following steps: 1) Transmetalation between CuOtBu and (Bpin)2 to generate a borylcopper species; 2) regiodivergent borylcupration of alkenes; 3) oxidation of the thus-generated C-Cu bond to give an alkyl radical; 4) trapping of the resulting alkyl radical by TEMPO.

Copper-boryl mediated organic synthesis

“…41 A number of other examples of copper-boryl-mediated heteroboration exist, for example stannylboration and oxyboration (Scheme 21). [103][104][105][106] 3. 10,12 and Hosomi 11 were the first to develop protocols for the borylation of a,b-unsaturated ketones and demonstrate complete regioselectivity for the b-borylation.…”

Directed C–H Alkenylation of Aryl Imines with Alkenyl Phosphates Promoted by a Cobalt–N‐Heterocyclic Carbene Catalyst

“…As a part of our exploration of cobalt‐catalyzed arene C–H functionalization with versatile imine directing groups,,, we have developed an ortho C–H alkenylation reaction of aryl imines with alkenyl phosphates, which is described herein (Scheme c). The key to the success of this reaction was an NHC ligand Cy IEt, which evolved through elaboration of the nitrogen substituents and backbone of the NHC. The present Co–NHC system was applicable to a variety of aryl imines and alkenyl phosphates, and proved to be complementary to Ackermann's alkenylation system.…”

Palladium/Copper‐catalyzed Oxidation of Aliphatic Terminal Alkenes to Aldehydes Assisted by p‐Benzoquinone

“…Unless otherwise indicated, all reactions were performed under an oxygen atmosphere (1 atm). PdCl 2 (MeCN) 2 , [20] 5-hexenyl benzyl ether, [21] 5-hexenoic acid benzyl ester, [22] and 5chloro-1-pentene [23] were prepared as described in the literature. t-BuOH was purchased from Nacalai tesque Co. Ltd. and was purified by distillation using CaH 2 .…”