Consecutive reduction, radical-cyclization, and oxidative-dehydrogenation reaction of ortho-substituted diboryl compounds

Abstract

An elegant synthetic route to a ladder-type di-borate compound 2a was reported based on the reduction, radical-cyclization, and oxidative-dehydrogenation reaction of 1. The existence of the biradical intermediate [1˙˙]2- was supported by both EPR measurements and DFT calculations.

Aryl Insertion vs Aryl–Aryl Coupling in C,C-Chelated Organoborates: The “Missing Link” of Tetraarylborate Photochemistry

“…There exist few examples of tetracoordinate 9-borafluorene anions in the literature, with each requiring elaborate synthetic strategies . We developed a new two-step protocol starting from 2,2′-dilithiobiphenyl (for Li­[1 H ] – Li­[3 H ] ) or its 4,4′- tert -butyl-substituted derivative (for Li­[1 t Bu ] – Li­[3 t Bu ] ) and the appropriate borane, followed by cation exchange with KO t Bu.…”

“…The crystal structures of Li­[1 H ] , Li­[1 t Bu ] , Li­[2 H ] , and Li­[3 t Bu ] were determined by single-crystal X-ray diffraction (see SI). The B–C bond lengths in Li­[1 H ] , Li­[1 t Bu ] , Li­[2 H ] , and Li­[3 t Bu ] (1.628(8)–1.678(4) Å) are comparable to those of other C,C-chelate 5 H -dibenzo­[ b , d ]­borol-5-ides as well as the neutral B,N-analogues. ,, …”

Molecular Quantum Dot Cellular Automata Based on Diboryl Monoradical Anions

“…The diradical dianion of a diboryl compound 1-Mes (2,2″-bis(dimesitylboranyl)-1,1′:4′,1″-terphenyl) was recently observed by electron paramagnetic resonance (EPR) measurements. 40 On the basis of this kind of π-conjugated spacer-linked diboryl structure, herein we proposed a new MQCA candidate system (diboryl monoradical anions) in which the charge was mainly localized on one boron atom and can be switched upon an electrostatic stimulus. We focus on the theoretical exploration of the eligibility of such kind of diboryl monoradical anions (e.g., 1-Mes •− ) as MQCA candidates.…”

“…COMPUTATIONAL DETAILS All geometry optimizations and single-point energy calculations were carried out at the (U)CAM-B3LYP/6-31G(d) level of theory, which has been proven to be robust in describing the electronic structures of diboryl compounds. 40 Vibrational frequency calculations were carried out to confirm that all optimized geometries correspond to energy minima. The energy of the lowest unoccupied molecular orbital (LUMO) for 1 was evaluated at the B3LYP/6-311+G(d,p) level, which proves to perform well in predicting the half-wave reduction potential for arylborane compounds in experimental cyclic voltammogram measurements.…”

Persistent P-Stabilized Boryl Radicals with Bulky Substituents at Boron

“…We are not aware of any related radical dimerization involving an m-terphenyl moiety, but the formation of [2b] 2 is somewhat reminiscent of the radical coupling/cyclization observed upon crystallization of the persistent diboryl biradical dianion E (Scheme 4). 14 The latter process induces dearomatization of the central ring of the p-terphenyl spacer and results in a ladder-type diborate derivative.…”