C-C单键的选择性硼氢化在化学工业中提出了基本挑战。以前,仅使用贵金属Ir和Rh的催化系统,与N-和P-配体结合,可以做到这一点,确保键裂解和选择性。与此形成鲜明对比的是,我们发现了一种用于C-C单键硼氢化的前所未有的通用无过渡金属系统。该方法不含过渡金属和配体,并且在化学和区域选择性方面超越了过渡金属系统,基材多功能性,或收益率。此外,我们的系统容忍各种官能团,如Ar-X(X=卤化物),杂环,酮,酯类,酰胺,硝基,腈,和C=C双键,它们通常在过渡金属的存在下容易发生硼氢化。因此,具有不同结构和功能的不同范围的γ-硼酸化胺已经容易地获得。实验机理研究,密度泛函理论(DFT),和内在键轨道(IBO)计算揭示了氢硼烷促进的C-C键裂解和氢化物转移反应途径。酰胺的羰基抑制游离N-H和氢硼烷之间的脱氢。酰胺的氮上的孤对电子促进环丙烷中C-C键的裂解。
Selective
hydroboration of C-C single bonds presents a fundamental challenge in the chemical industry. Previously, only catalytic systems utilizing precious metals Ir and Rh, in conjunction with N- and P- ligands, could achieve this, ensuring bond cleavage and selectivity. In sharp contrast, we discovered an unprecedented and general transition-metal-free system for the
hydroboration of C-C single bonds. This methodology is transition-metal and ligand-free and surpasses the transition-metal systems regarding chemo- and regioselectivities, substrate versatility, or yields. In addition, our system tolerates various functional groups such as Ar-X (X = halides), heterocyclic rings, ketones, esters, amides, nitro, nitriles, and C=C double bonds, which are typically susceptible to
hydroboration in the presence of transition metals. As a result, a diverse range of γ-boronated amines with varied structures and functions has been readily obtained. Experimental mechanistic studies, density functional theory (DFT), and intrinsic bond orbital (IBO) calculations unveiled a hydroborane-promoted C-C bond cleavage and hydride-shift reaction pathway. The carbonyl group of the amide suppresses dehydrogenation between the free N-H and hydroborane. The lone pair on the nitrogen of the amide facilitates the cleavage of C-C bonds in cyclopropanes.