Palladium‐Catalyzed Cascade Deboronation/Regioselective B−P Coupling of closo‐Carboranes

Abstract

A cascade deboronation/regioselective BÀ P coupling of closocarboranes is disclosed using a combination of palladium catalysts and nitrogen or phosphine-containing directing groups. Unsymmetric C-substituted closo-carboranes, including C-monosubstituted and unsymmetric 1,2-disubstituted closocarboranes, are tolerated. Select closo-carboranes bearing other directing groups, such as benzoxazole, and diphenylphosphine, are compatible substrates for this reaction. Phosphine and arsenic can be utilized as effective coupling partners. Furthermore, a catalytic amount of palladium salt mediates the regioselective BÀ H activation process. Readily available closocarboranes as the starting materials for direct one-pot synthesis of functionalized nido-carboranes and the in-situ formation of nido-carborane intermediates without purification are important features in terms of practical applications.

Pd-Catalyzed Selective B(6)–H Phosphorization of nido-Carboranes via Cascade Deboronation/B–H Activation from closo-Carboranes

“…31 P NMR (162 MHz, CDCl 3 ): δ 5.88 (q, J = 161.1 Hz). The data are consistent with the reported one …”

“…Thus far, only one precedent starting from closo -carboranes has been reported. More recently, our group has disclosed the directed deboronation/B(11)–H phosphorization of nido -carboranes using C-substituted o -carborane substrates (Scheme d) . However, these methods mentioned above are strongly limited to exo -cage B­(9,10,11)–H bonds on the open C 2 B 3 pentagonal plane of nido -carboranes, which is capped by an extra bridging hydrogen atom (B–H–B).…”

Recent Progress in B—H Bond Functionalization of nido-Carboranes

“…作者对目标化合物的光学性质 进行探究, 结果表明该化合物能够增强固态发光效率, 为硼基光功能分子设计提供了新策略(Scheme 22). 2022 年, 陆居有课题组 [34] 报道了一种配位导向的 巢式-碳硼烷 B(…”

Activation of Alkynes by a Redox-Active Carboranyl Diphosphine and Formation of Boron-Containing Phosphacycles

“…In contrast, the carborane B–H bonds are rather strong, with a bond dissociation energy estimated at 118 kcal/mol (comparable to aromatic C–H bonds). The chemistry of these boron vertices shares similarities with arene chemistry, and the functionalization usually proceeds through electrophilic substitution promoted by Lewis acids or by oxidative addition to electron-rich late transition metal centers. , Recently, the development of new transition metal-catalyzed coupling methods has significantly expanded the library of B-substituted carboranyl derivatives. − In addition to closo -{C 2 B 10 } cages, there has been a significant progress in the selective B-H bond functionalization for nido -{C 2 B 9 } clusters. , …”