Reactions of Tetra(o‐tolyl)diborane(4) with Organic Azides: Formation of Fluorescent Boron‐Fused Hexazenes

Abstract

The reaction of tetra(o‐tolyl)diborane(4) with organic azides afforded three different compounds, diborylamines, diboryltriazenes, and B2‐hexazenes having a bicyclic B2N6 ring system. The reaction with aryl azides gave diborylamines, while the reaction with 1 equiv. of alkyl azides furnished diboryltriazenes. In the case of the reaction with an excess amount of primary alkyl azide, a new heterocyclic B2‐hexazenes were obtained. The formation of the B2N6 structure could be explained by one general reaction mechanism via the diboryltriazene intermediate according to the control experiments and DFT calculations. The B2‐hexazenes exhibited a strong fluorescence with a remarkably high fluorescent quantum yield of up to 96 %.

Boryls, their compounds and reactivity: a structure and bonding perspective

“…5,52,53 Over the years (2014–2023), by collaborating with the research teams of Yamashita and Braunschweig, we have investigated the mechanism of reactions of various diboranes(4) with a range of unsaturated organic and inorganic molecules, including carbon monoxide, alkynes, nitriles, and azides. 54–60 Through our DFT studies, we have elucidated the dual reactivity of diboranes(4), i.e. , exhibiting both electrophilic and nucleophilic properties, and how this unique characteristic enables various transformations upon reacting with these molecules.…”

“…Recently, reactions of tetra( o -tolyl)diborane(4) with organic azides were reported. 59 The reaction of tetra( o -tolyl)diborane(4) with 1 equiv. of aryl azides (PhN 3 or MesN 3 ) was found to result in an insertion of “aryl nitrene” into the B–B bond to give a diborylamine product ( eqn (10) ).…”

Avenue to novel o-carboranyl boron compounds – reactivity study of o-carborane-fused aminoborirane towards organic azides

“…Organic azides, since the rst report in 1864, 37 have attracted wide attention due to their energy-rich and variable reactivities. 38,39 The nitrogen-rich N 3 group exhibits diverse reactivity with electron-decient boron compounds, including forming Lewis acid-base adducts, 40 1,3-dipolar cycloadditions with B] B/N bond, [41][42][43][44][45] nitrene insertion into the B-B/C bond with concomitant loss of N 2 , 42,[46][47][48][49][50][51][52][53][54][55][56] and terminal nitrogen insertion into B-B/C bonds. [55][56][57][58] Thus, organic azides are promising candidates for the construction of BN-containing compounds through their reactions with electron-decient boron compounds.…”