Aryne Generation from <i>o</i>-Triazenylarylboronic Acids Induced by Brønsted Acid

Abstract

We report aryne generation from 2-triazenylarylboronic acids using an activator such as Brønsted acids, Lewis acids, and solid acids. With the use of ( )-Camphorsulfonic acid [( )-CSA], the aryne precursors provided cycloadducts with a range of arynophiles in high yields. Aryne generated under the acidic conditions underwent chemoselective cycloaddition with a furan in the presence of a basic arynophile, namely an amine. Hammett plot analyses revealed that an aryne generation mechanism induced by ( )-CSA is distinct from the mechanism induced by silica gel.

Functionalization of Siloxanes with Arynes Generated from <i>o</i>-Triazenylarylboronic Acids

“…o-Triazenylphenylboronic acids 1a-d were synthesized by our previously reported method. 19,21) 3-Azidopropyl-POSS 2b, 9) 3-aminopropyl-POSS 2f 29) were synthesized according to the literature procedures. See Supplementary Materials for the structures of compounds I through V.…”

“…Recently, we developed o-triazenylarylboronic acid 1 as a novel precursor of arynes [15][16][17][18][19][20][21][22] (Chart 2a). These precursors are readily available from the corresponding o-iodoanilines and are shelf-stable solids.…”

“…Despite their stability, arynes can be generated under mild conditions using silica gel as the activator, making a broad range of arynophiles applicable to reactions with o-triazenylarylboronic acid 1. A salient feature of the proposed method is its compatibility with reactions of arynophiles with silyl ether moieties, 19) which is hardly possible with conventional methods using a combination of o-trimethylsilylaryl triflates and fluoride salts. [23][24][25][26] In this context, this study reports the functionalization of POSS and related siloxanes bearing arynophilic moieties with arynes using o-triazenylarylboronic acids as precursors (Chart 2b).…”

Switchable chemoselective aryne reactions between nucleophiles and pericyclic reaction partners using either 3-methoxybenzyne or 3-silylbenzyne

“…Recently, McCormick et al developed an arynophilicity parameter to describe the relative reactivity of various arynophiles with respect to 3-chlorobenzyne 32 . Besides, there are some other competitive aryne reaction examples 33 , 34 .…”

“…Recently, McCormick et al developed an arynophilicity parameter to describe the relative reactivity of various arynophiles with respect to 3-chlorobenzyne 32 . Besides, there are some other competitive aryne reaction examples 33,34 . It has been commented by Hergenrother that "Can robust predictive models for site-and chemoselectivity of this and other (aryne) methodologies be developed?…”