Facile Access to Substituted 1,4‐Diaza‐2,3‐Diborinines

Abstract

Several bis(dimethylamino)‐substituted 1,4‐diaza‐2,3‐diborinines (DADBs) were synthesized with variable substituents at the backbone nitrogen atoms. By reaction with HCl or BX3 (X=Br, I), these species were successfully converted into their synthetically more useful halide congeners. The high versatility of the generated B−X bonds in further functionalization reactions at the boron centers was demonstrated by means of salt elimination (MeLi) and commutation (NMe2 DADBs) reactions, thus making the DADB system a general structural motif in diborane(4) chemistry. A total of 18 DADB derivatives were characterized in the solid state by X‐ray diffraction, revealing a strong dependence of the heterocyclic bonding parameters from the exocyclic substitution pattern at boron. According to our experiments towards the realization of a Dipp‐substituted, sterically encumbered DADB, the mechanism of DADB formation proceeds via a transient four‐membered azadiboretidine intermediate that subsequently undergoes ring expansion to afford the six‐membered DADB heterocycle.

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

“…The reaction of 292 with BH 3 SMe 2 at room temperature produces 1,2-dihydrodiborane(4) derivatives 293 [ 139 ]. By reacting with HX or commuting with BX 3 , the unreactive NMe 2 groups of 292 can be readily substituted by halides [ 140 ]. When 1,2-dihydrodiboranes(4) 294 in benzene reacts with an excess of trimethylsilyl azide, 1,2-diazidodiboranes(4) 295 are cleanly obtained.…”