124215-50-5Relevant articles and documents
The influence of boryl substituents on the formation and reactivity of adjacent and vicinal free radical centers
Walton, John C.,McCarroll, Andrew J.,Chen, Qiao,Carboni, Bertrand,Nziengui, Roger
, p. 5455 - 5463 (2000)
Radicals containing α-boronate substituents were generated by bromine abstraction from 1-bromo-alkyldioxaborolanes (boronic esters), by addition to vinyl boronate, and by hydrogen abstraction from alkyldioxaborolanes and observed by EPR spectroscopy. Unsymmetrically substituted α-boronate radicals displayed selective line broadening in their low-temperature spectra from which barriers to internal rotation about ?CH2-B(OR′)OR bonds were found to be 3 ± 1 kcal mol-1. Use of an empirical relationship between barrier height and bond dissociation energy led to BDE[(RO)2BCH2-H] = 98.6 kcal mol-1. Rate constants for hydrogen abstraction from 2,4,4,5,5-pentamethyl-1,3,2-dioxaborolane by tert-butoxyl radicals were determined from competitive EPR and product studies and found to be relatively small, comparable to those of unactivated methyl groups. Hydrogen abstraction from bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-methane was found to be extremely difficult. The structures and energetics of α-boronate radicals were computed by DFT methods (B3LYP/6-31G*). This predicted reductions in the rotation barriers of X2B-CH2? radicals for increasing alkoxy substitution at B (X = Me or MeO) and corresponding increases in the X2BCH2-H bond dissociation energies. The B3LYP-computed BDE[(MeO)2BCH2-H] was in excellent agreement with the analogous value derived from the experimental rotation barrier. Radicals containing β-boronate substituents were generated from the corresponding 2-bromoalkylboronic esters and characterized by EPR spectroscopy. At higher temperatures the main product from trialkyltin and triethylsilyl radical promoted reactions of 2-(2-bromohexyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was 1-hexene. This was best accounted for by a mechanism involving initial SH2 attack on the borolane and subsequent bromine atom elimination from the displaced 2-bromohexyl radical.
Iridium-catalyzed hydroboration of alkenes with pinacolborane
Yamamoto, Yasunori,Fujikawa, Rhyou,Umemoto, Tomokazu,Miyaura, Norio
, p. 10695 - 10700 (2004)
Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]2 gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]2 resulted in the best yields for vinylarenes such as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes. Graphical Abstract.
Decarboxylative Borylation of mCPBA-Activated Aliphatic Acids
Wei, Dian,Liu, Tu-Ming,Zhou, Bo,Han, Bing
supporting information, p. 234 - 238 (2020/01/02)
A decarboxylative borylation of aliphatic acids for the synthesis of a variety of alkylboronates has been developed by mixing m-chloroperoxybenzoic acid (mCPBA)-activated fatty acids with bis(catecholato)diboron in N,N-dimethylformamide (DMF) at room temperature. A radical chain process is involved in the reaction which initiates from the B-B bond homolysis followed by the radical transfer from the boron atom to the carbon atom with subsequent decarboxylation and borylation.
Silver-Catalyzed anti-Markovnikov Hydroboration of C-C Multiple Bonds
Wang, Yan,Guan, Rui,Sivaguru, Paramasivam,Cong, Xuefeng,Bi, Xihe
supporting information, p. 4035 - 4038 (2019/06/14)
A simple silver salt (AgOAc)-catalyzed anti-Markovnikov-selective hydroboration of alkenes, 1,3-dienes, and alkynes with pinacolborane (HBpin) has been described. This strategy provides an efficient and practical method to access various alkyl-, allyl-, a
