Synthesis, Structure, and Reactivity of Acid‐Free Neutral Oxoborane

Abstract

An efficient synthesis of an acid‐free neutral oxoborane of the type carboranyl‐B(carbene)=O has been developed via a serendipitous discovery from the reaction of 1,2‐[BBr(carbene)]‐o‐carborane with AgOTf. This represents a new type of oxoborane. The stabilization of this oxoborane may be attributed to 1) kinetic stabilization provided by a bulky 3D carboranyl ligand and 2) thermodynamic stabilization offered by a carbene ligand. Crystallographic analyses support the presence of the shortest terminal B=O double bond ever reported thus far. Its reactivity has also been examined.

Ring-opening and ring-expansion reactions of carborane-fused borirane

“…The B(13)–O(1) distance of 1.429(3) Å falls in the range of the reported B–O single bond distances (1.35–1.52 Å). 34–36 It was noted that only one diastereomer of 8 was obtained as confirmed by the NMR data. This can be ascribed to steric reasons since the NHC and Ph groups are in the trans positions in the structure with respect to the C(1)C(2)C(38)O(1)B(13) five-membered ring.…”

“…Following our previous procedures, 34 reaction of 1-Li- o -carborane with BBr 3 in the presence of 1,3-bis-(2,6-diisopropylphenyl)imidazole-2-ylidene (Idipp) afforded a carbene-coordinated carboranyl dibromoborane ( 1 ) in 54% isolated yield. Treatment of 1 with 1 equiv.…”

Ir-Catalyzed Regioselective Dihydroboration of Thioalkynes toward Gem-Diboryl Thioethers

“…Without modification, the dihydroboration protocol could also be applied in a 2-mmol scale reaction of 1a without erosion in reaction efficiency and selectivity (Scheme ). The α-sulfenyl gem -diboryl products represent a type of rarely known structure featuring a tetra-substituted carbon center bearing two boryl groups and one sulfenyl group . To demonstrate their reactivity and utility, we carried out a transformation to selectively convert one of the two boronate units with an alkyl bromide by cross-coupling (Scheme ).…”

Functionalization of o-carboranes via carboryne intermediates

“…Similar to benzyne, 31 o-carboryne can be trapped by transition metals to form a series of metal-carboryne species, 30,[32][33][34][35] or by boron to generate carborane-fused boriranes. [36][37][38][39] It is noted that another type of metal-carboryne complex in which a transition metal is s-bonded to two cage B atoms of m-carborane has also been known. [40][41][42] The structures of the aforementioned metal complexes resemble that of metalbenzyne complexes.…”