Poly‐Boron, ‐Silicon, and ‐Gallium Lewis Acids by Hydrometallation of 1,5‐ and 1,8‐Dialkynylanthracenes

Abstract

1,5‐Dialkynylanthracenes and 1,8‐dialkynylanthracenes have been functionalised by a series of hydrometallation reactions, namely, hydrosilylation, hydroboration and hydrogallation. Nine anthracene‐based Lewis acidic compounds with a semiflexible organic framework bearing SiCl3, SiCl2Me, SiClMe2, B(C6F5)2 and GaCl2 substituents were obtained. In all cases, the substrate could be functionalised twice, and bidentate Lewis acids were obtained. By using Piers' borane [HB(C6F5)2], a fourfold‐substituted anthracene species functionalised with four extremely electronegatively substituted boron atoms could be generated in quantitative yield. All of the poly‐Lewis acids were characterised by multinuclear NMR spectroscopy and, in part, by mass spectrometry and X‐ray diffraction experiments.

Geminal bis-borane formation by borane Lewis acid induced cyclopropyl rearrangement and its frustrated Lewis pair reaction with carbon dioxide

“…Although such geminal bis-boranes are principally readily available from terminal alkynes by sequential hydroboration reactions with two molar equivalents of HB(C 6 F 5 ) 2 , as it has been shown by Piers et al , 1,2 surprisingly little is known about this CO 2 -trapping reaction. Stephan et al had used Siebert's unsaturated geminal BCl 2 compound 1 (ref.…”

Tridentate Lewis Acids: Boron‐, Silicon‐ and Gallium‐Functionalised Tris(dimethylsilyl)methanes

“…The effect of increasing the substitution of the terminal silicon atoms by chlorine atoms is also observable for 13-15 (Table 3). [a] n = 1 (13), n = 2 (14), n = 3 (15).…”

“…Examples of our ongoing research include other semiflexible 1,5-and 1,8-diethynylanthracene scaffolds functionalised by hydrometallation. [14] During these studies the formation of host-guest complexes between the bidentate Lewis acid 1,8-bis[(diethylgallanyl)ethynyl]anthracene and pyridine or pyrimidine was investigated under dynamic conditions in solution by afforded flexible poly-Lewis acids equipped with B(C 6 F 5 ) 2 , SiCl 3 , SiMeCl 2 and SiMe 2 Cl substituents. The reaction of these siliconcontaining tridentate Lewis acids with SbF 3 led to fluorinesubstituted poly-Lewis acids of the type Me 3 SiC-[Si(Me) 2 CH 2 CH 2 SiMe 3-n F n ] 3 (n = 1-3).…”

“…[21] In addition to cyclic poly-Lewis acids, Uhl and co-workers have achieved outstanding progress in constructing multi-dentate Lewis acids through the hydrometallation of unsaturated substrates with dialkylgallium [22][23][24] and dialkylaluminium hydrides. [22,23,25] Further poly-Lewis acids based on chlorogallane groups [14] have been synthesised in reactions between dichlorogallane, (HGaCl 2 ) 2 , and unsaturated scaffolds. [26] Herein we report new trisilylmethane-based flexible scaffolds, their synthesis and efficient preparative functionalisation to afford a series of boron, gallium and electronegatively substituted silicon-containing tridentate Lewis acids.…”

Bidentate Lewis Acids Derived from o‐Diethynylbenzene with Group 13 and 14 Functions

“…[18] Recently, we reported the synthesis of a series of directed, bidentate and semiflexible Lewis acids based on an alkynyl‐substituted anthracene backbone in which the Lewis acid functions are introduced by means of hydrosilylation and hydroboration. [19] …”