The Preparation and Stabilization of Acetylenic Boranes^1a

Synthesis, Structures, and Donor−Acceptor Adducts of Tris(3,3-dimethyl-1-butynyl)borane

“…Another approach was described by Ashby et al [2] who treated sodium acetylide or sodium organylacetylides with boron trifluorideϪamine to yield the corresponding amineϪB-(CϵCH 3 ) 3 adducts [amine ϭ C 5 H 5 N, (CH 3 ) 3 N, (CH 3 ) 2 NH], and H 5 C 5 NϪB(CϵCC 6 H 5 ) 3 . Köster et al [3] prepared tris(alkynyl)boraneϪtrimethylamine adducts by oxidizing alkynylborane adducts of trimethylamine with trimethylamine oxide, the resulting alkynylbis(alkoxy)boranes rearrange to form tris(alkynyl)boraneϪtrimethylamine and tris(alkoxy)borane.…”

“…Attempts to synthesize donor-free tris(alkynyl)boranes led to polymeric products. [2] We report here on the synthesis of tris(3,3-dimethyl-1-butynyl)borane (1), the first donor-free tris(alkynyl)borane. Furthermore, the NMR spectroscopic and structural data [a] of 1 and of its pyridine, triphenylphosphane, and tetrahydrofuran adducts 2aϪc are described.…”

A Mild Benzannulation through Directed Cycloaddition Reactions

“…However, exposing a pure sample of 3 a to in situ generated alkynyldifluoroborane resulted in less than 5 % conversion (as judged by 400 MHz 1 H NMR spectroscopy), thus suggesting that 3 b , c do not originate from the aryl difluoroborane 3 a itself (Scheme ). Alternatively, disproportionation of alkynyldifluoroboranes to trialkynylboranes may be promoted by pyridine 12. 13 We therefore postulate that alkynylated products 3 b , c are formed from cycloaddition of intermediates such as A .…”

Carbo-mers: from skeleton to function

“…While the preparation of sodium tetraalkynylborate 107 and ammonium tetraalkynylborate 108 were already known, the first synthesis of trialkynylboranes was described in 1964. 109 All attempts to prepare triethynylborane either from BF 3 , BCl 3 or B(OMe) 3 and sodium acetylide resulted in the formation of polymeric compounds. Amine complexes were however successfully obtained by reaction of sodium acetylide with the corresponding amine-boron halide adducts (Scheme 24).…”