96%89694-50-8Relevant articles and documents
Acid-promoted metal-free protodeboronation of arylboronic acids
Zhang, Guoqing,Li, Yang,Liu, Jianhui
, p. 34959 - 34962 (2017/07/25)
A facile acid-promoted protodeboronation of arylboronic acids in the absence of metal catalysts or any other additives is described. This protodeboronation is general for a range of arylboronic acids with both electron-donating and electron-withdrawing groups in good to excellent yields under air atmosphere. Density functional theory mechanistic studies showed that the protodeboronation of arylboronic acids followed an intermolecular metathesis via a four-membered ring transition state. The effect of the substituent of arylboronic acids in protodeboronation is also theoretically studied.
Solid-supported ortho-iodoarylboronic acid catalyst for direct amidation of carboxylic acids
Gernigon, Nicolas,Zheng, Hongchao,Hall, Dennis G.
, p. 4475 - 4478 (2013/07/26)
Amides are a ubiquitous class of organic compounds endowed with great utility. There is a need for simple and effective catalytic methods for their direct formation from carboxylic acids and amines as a way to avoid the use of coupling reagents. We have designed a recyclable resin-supported derivative of 5-methoxy-2-iodophenylboronic acid as a heterogeneous catalyst active in ambient conditions for promoting direct amidations of aliphatic carboxylic acids and amines. The optimal, practical procedure involves a simple double-filtration to isolate the amide product while separating the catalyst from residual molecular sieves.
Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: Catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect
Gernigon, Nicolas,Al-Zoubi, Raed M.,Hall, Dennis G.
, p. 8386 - 8400,15 (2012/12/11)
The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state.
Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: Catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect
Gernigon, Nicolas,Al-Zoubi, Raed M.,Hall, Dennis G.
, p. 8386 - 8400 (2013/01/15)
The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state.
BORONIC ACID CATALYSTS AND METHODS OF USE THEREOF FOR ACTIVATION AND TRANSFORMATION OF CARBOXYLIC ACIDS
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Page/Page column 38-39, (2012/09/10)
The present application provides methods and catalysts for activation of carboxylic acids for organic reactions. In particular, methods are disclosed for direct nucleophilic addition reactions, such as, amidation reactions with amines, cycloadditions, and conjugate additions, using boronic acid catalysts of formula I, II or III: Also included are novel boronic acid catalysts of formula IV, V and III:
Mild silver(I)-mediated regioselective iodination and bromination of arylboronic acids
Al-Zoubi, Raed M.,Hall, Dennis G.
supporting information; experimental part, p. 2480 - 2483 (2010/08/07)
A convenient and regioselective silver(I)-mediated electrophilic iodination and bromination reaction of arylboronic acids has been developed. The boronic acid does not require protection prior to the reaction, which can be performed on a multigram scale with moderate to excellent yields. A mild, simple, and effective method is disclosed to provide ortho-haloarylboronic acids that can be used as useful intermediates in selective sequential Suzuki-Miyaura cross-coupling reactions to provide ortho-triaryl derivatives in good yields.
