Transition-Metal-Free Borylation of Aryltriazene Mediated by BF₃·OEt₂

Abstract

A practical and simple method for deaminoborylation of aryltriazene with bis(pinacolato)diboron has been developed that is mediated by BF(3)·OEt(2). Various arylboronic esters are prepared in moderate to good yields with this facile transition-metal-free procedure.

On the mechanism of photocatalytic reactions with eosin Y

“…When we performed the borylation reaction according to the literature report [21] but without the addition of the photocatalyst eosin Y, 54% yield of the borylation product were obtained by direct photolysis (Scheme 4). These observations are in full accord with a report of direct reaction of thermally generated aryl cations (from arenediazonium salts) with bispinacolato diboron to give the corresponding arylborinic esters [31]. It is thus very likely that direct light-triggered heterolysis of the starting material accounts for substantial amounts of product formation under conditions which were believed to proceed through photocatalytic SET.…”

Synthesis, Structure, and Reactivity of Anionic sp2–sp3 Diboron Compounds: Readily Accessible Boryl Nucleophiles

“…Yamane and Zhu’s study of the transition‐metal‐free borylation of aryl triazenes showed that an aryl diazonium salt could be borylated by 1 at room temperature in methanol 39. We verified Yamane and Zhu’s yield of about 40 % for the reaction of [4‐MeO‐C 6 H 4 N 2 ][BF 4 ] and 1 in MeOH.…”

“…When a drop of methanol was introduced to the system, the respective product was observed to form more rapidly, albeit still at a reduced rate relative to the reaction in pure methanol 26. 39 Thus, it is possible that [B 2 pin 2 F] − is formed from 1 and BF 4 − in MeOH, as suggested by Yamane and Zhu. Reaction of 8 with [4‐MeO‐C 6 H 4 N 2 ][BPh 4 ] in [D 3 ]MeCN was also examined, and a similar product ratio was obtained to that found when the diazonium salt with a [BF 4 ] − cation was used.…”

“…This slight improvement in reactivity and the results from many reported transition‐metal‐free borylation reactions indicate that methanol is required to facilitate the formation of organoboronate esters and further research is ongoing into the dependence of transition‐metal‐free borylation systems on methanol 23. 37, 39…”

Synthesis of Aryl Trimethylstannanes from Aryl Amines: A Sandmeyer‐Type Stannylation Reaction

“…[4] A different strategy is the nucleophilic substitution between aryl halides or aryl ammonium salts and trialkyl stannyl anion (Scheme 1 b). [8][9][10] We have recently reported a new approach towards aryl boronic pinacol esters with aromatic amines as starting materials. [6] The Sandmeyer-type transformation is a classical and valuable approach in which the amino group can be converted into various functional groups, such as halogen, cyano, hydroxy, and sulfonate groups.…”