Gold-Catalyzed Proto- and Deuterodeboronation

Abstract

A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.

Rapid Iododeboronation with and without Gold Catalysis: Application to Radiolabelling of Arenes

“…It is worth noting that the reaction is not sensitive to air or moisture, and thus, it is a very practical, as well as fast, procedure. In fact, wet solvent enhanced the yields for the gold‐catalysed reaction (see the Supporting Information) …”

“…In fact, wet solvente nhanced the yields for the gold-catalysed reaction (see the Supporting Information). [13] Next, the substrate scope of the gold-catalysed and uncatalysed reactions were investigated under these optimised conditions (Table 3). Both the catalysed and uncatalysed reactions were run concurrently for all substrates to ascertain whether gold catalysis offered anya dvantage over the uncatalysed reaction or vice versa.…”

“…Our interest in this area arose from our previous work on gold catalysis; in particular, the mild gold‐catalysed proto‐ and deuterodeboronations and cross‐couplings (Scheme A (a) and (b), respectively) . We hypothesised that the organogold intermediate I should react with NIS to rapidly form iodoarenes 3 .…”

“…Our interest in this area arose from our previousw ork on gold catalysis; [11] in particular, the mild gold-catalysed [12] protoand deuterodeboronations [13] and cross-couplings (Scheme 1A(a) and (b), respectively). [14] We hypothesisedt hat the organogold intermediate I [15] should reactw ith NIS to rapidly form iodoarenes 3.T herefore,o ur aims were to 1) compare the gold-catalysed andu ncatalysed reactions to ascertain whether gold catalysis can be used to overcome some of the substrate scopel imitations of the uncatalysed reaction, 2) develop a much faster iodination protocol, both catalysed and uncatalysed,3 )utilise environmentally friendly solvents to significantly improvet he practicality of the reaction( the original reaction times were 1.5-25 hi na cetonitrile), [6] and 4) to apply the methodology to radioiododeboronations.…”

Auto‐Tandem Catalysis: PdII‐Catalysed Dehydrogenation/Oxidative Heck Reaction of Cyclopentane‐1,3‐diones

“…Under strictly anhydrous conditions, it was thought that the aryl pinacol boronic esters 9 struggle to transmetallate in the absence of base, thereby resulting in low yields of 2 aa and 2 ac . This prompted us to attempt the reaction under “wet conditions”: non‐anhydrous solvents and non‐dried glassware, in the hope that residual water in the solvent will be sufficient to help promote transmetallation., Pleasingly, these “wet” conditions resulted in significant improvement in yields: from 45 to 77 % in the case of 3 aa and 35 to 68 % in the case of 2 ac (Table ). These non‐anhydrous conditions were thus applied to the subsequent substrate scope studies (Tables and ).…”