1,2-Dialkynyldiboranes(4): B–B versus CC bond reactivity

Abstract

The reactivity of three 1,2-dialkynyl-1,2-diaminodiborane(4) derivatives, B2(NMe2)2(C≡CR)2 (R = H, Me, SiMe3), towards small molecules known to react with both B–B and C≡C bonds was studied. With arylazides nitrene insertion...

Reactions of main group compounds with azides forming organic nitrogen-containing species

“…In 2022, the Braunschweig group described the reactions of 1,2-dialkynyl-1,2-diaminodiborane with azides. 48 The reactions of B14 with various azides afforded the nitrogen insertion product B14-P in 69–89% yield (Scheme 15). The cycloaddition of alkyne moieties with azides did not occur even in the presence of a Cu( i ) catalyst.…”

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

“…of aryl azides, PhN 3 or MesN 3 , resulted in the insertion of “aryl nitrene” into the B−B bond to give diborylamine 2 Ph or 2 Mes as colorless crystals in good yield (Scheme 2). A similar “nitrene”‐insertion into the B−B bond of 1,2‐dialkynyl‐1,2‐diamino‐diborane(4) has been recently reported to form A [9] . It should be emphasized that the reaction of 1 with an excess amount of aryl azides did not alter the major product.…”

“…A similar "nitrene"-insertion into the BÀ B bond of 1,2-dialkynyl-1,2-diamino-diborane(4) has been recently reported to form A. [9] It should be emphasized that the reaction of 1 with an excess amount of aryl azides did not alter the major product. Considering both PhN 3 and MesN 3 afforded similar yields of products, the selectivity toward 2 R would be controlled by an electronic effect of the aryl group, rather than steric effect.…”

“…The B−N bond lengths [Figure 1, 2 Ph : 1.434(3), 1.467(3) Å; Figure S34, 2 Mes : 1.462(2), 1.453(2) Å] [10] in the crystal were in a similar range to those of A (av. 1.46 Å) [9] . The 1 H NMR spectra of 2 Ph and 2 Mes exhibit a single broadened signal of the methyl group in the o ‐tolyl groups, indicating the equal contribution of two resonance structures of B − =N + −B and B−N + =B − with slow B−N bond rotation in the NMR time scale.…”

“…1.46 Å). [9] The 1 H NMR spectra of 2 Ph and 2 Mes exhibit a single broadened signal of the methyl group in the o-tolyl groups, indicating the equal contribution of two resonance structures of B À =N + À B and BÀ N + =B À with slow BÀ N bond rotation in the NMR time scale.…”