Reaction Of Boronic Acids Research Articles

Unprecedented palladium-catalyzed cross-coupling reaction of alpha-bromo sulfoxides with boronic acids.

[reaction: see text] A new Suzuki-type palladium-catalyzed reaction of boronic acids with alpha-bromo sulfoxides has been developed using a protocol similar to the well-documented reaction of boronic acids with aryl halides. Both cross-coupling and homocoupling processes were observed. The best yields in cross-coupling products were obtained when the presence of oxygen was carefully excluded using degassed solvents. The oxidative addition palladium complex intermediate could be isolated and characterized by X-ray single-crystal diffraction.

A Mild, Nonbasic Synthesis of Thioethers. The Copper‐Catalyzed Coupling of Boronic Acids with N‐Thio(alkyl, aryl, heteroaryl)imides.

[reaction: see text] A new synthesis of thioethers is described. The reaction of boronic acids with aryl, heteroaryl, and alkyl N-thioimides in the presence of catalytic quantities of a Cu(I) carboxylate affords good to excellent yields of thioethers. This reaction takes place in the absence of a base under mild conditions (THF, 45-50 degrees C, 2.5-12 h) and represents an interesting complement to known methods for thioether synthesis.

A Convenient Method for Preparing Aromatic Ketones from Acyl Chlorides and Arylboronic Acids via Suzuki—Miyaura Type Coupling Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Kinetic study of the complex formation of boric and boronic acids with mono- and diprotonated ligands

The complex formation reactions of boric and boronic acids (RB(OH) 2: R=OH, n-Bu, Ph, and m-NO 2Ph) with 4-isopropyltropolone (Hipt) and chromotropic acid (H 2cht 2−) have been studied kinetically at various pH. The reactions of H 2ipt + with boronic acids were faster than those of Hipt by a factor of 1.5–11, and fully deprotonated ipt − also reacted with m-NO 2PhB(OH) 2, but slower than Hipt. The tetrahedral m-NO 2PhB(OH) 3 − ion did not react with Hipt. Reaction routes for the complexation of boric acid with chromotropic acid could not be specified because of the unexpected problem of proton ambiguity. Mechanism for the reactions of boronic acids with bidentate ligands was discussed in terms of rate determining chelate ring closure. It was concluded that at least one proton is necessary for the OH − in the tetrahedral intermediates to be eliminated smoothly as water, and a doubly hydrogen-bonded intermediate was proposed for the reactions with diprotic ligands.

A convenient method for preparing aromatic ketones from acyl chlorides and arylboronic acids via Suzuki–Miyaura type coupling reaction

Aromatic ketones are synthesized efficiently via palladium-catalyzed cross-coupling reaction of boronic acids with acyl chlorides in the presence of K 3PO 4 hydrate in toluene. This allows the use of aliphatic acyl chlorides as the starting material. Hydrated water plays a significant role as an H 2O source to activate the catalytic system.

A mild, nonbasic synthesis of thioethers. The copper-catalyzed coupling of boronic acids with N-thio(alkyl, aryl, heteroaryl)imides.

[reaction: see text] A new synthesis of thioethers is described. The reaction of boronic acids with aryl, heteroaryl, and alkyl N-thioimides in the presence of catalytic quantities of a Cu(I) carboxylate affords good to excellent yields of thioethers. This reaction takes place in the absence of a base under mild conditions (THF, 45-50 degrees C, 2.5-12 h) and represents an interesting complement to known methods for thioether synthesis.

Pinacolyl boronic esters as components in the Petasis reaction

The multicomponent reaction of boronic esters with imine or iminium species (generated in situ by reaction of amines with glyoxylic acid) has received little attention in the literature despite the current interest in the corresponding reactions of boronic acids (Petasis reaction). Moreover, the use of boronic esters in this reaction is particularly attractive since chiral esters could act as auxiliaries in a novel enantioselective process. We set out to establish whether boronic esters were general substrates in the Petasis reaction. Pinacolyl boronic esters were selected for study as a model substrate for more complex homochiral boronic esters because of their ease of synthesis and chemical stability. We found that pinacolyl boronic esters do not react with imines derived from primary amines and glyoxylic acid under standard conditions. By contrast, imines derived from secondary amines and glyoxylic acid react readily with vinylboronic esters but less readily with heteroaryl- or arylboronic esters.

Rhodium-catalysed addition of arylboronic acids to oxabenzonorbornadienes.

The facile addition reaction of boronic acids to oxabenzonorbornadienes was achieved using a catalytic amount of a rhodium(I) complex having P(OEt)3 ligands, affording cis-2-aryl-1,2-dihydro-1-naphthol stereoselectively, and in good yield without concomitant deboronation of the boronic acid.

Universal solid-phase approach for the immobilization, derivatization, and resin-to-resin transfer reactions of boronic acids.

Boronic acid-containing molecules are employed in a broad range of biological, medicinal, and synthetic applications. These compounds, however, tend to be difficult to handle by solution-phase methods. Herein, this problem is addressed with the development of the first general solid-phase approach for the derivatization of functionalized boronic acids. This approach is based on the use of a diethanolamine resin anchor that facilitates boronic acid immobilization by avoiding the need for exhaustive removal of water in the esterification process. The immobilization of a wide variety of boronic acids onto N,N-diethanolaminomethyl polystyrene (DEAM-PS, 1) can be performed within minutes by simple stirring in anhydrous solvents at room temperature. Evidence for the formation of a bicyclic diethanolamine boronate with putative N-B coordination was shown by (1)H NMR analysis of DEAM-PS-supported p-tolylboronic acid. The hydrolytic cleavage of the same model boronic acid from the DEAM-PS resin was studied by UV spectroscopy. Hydrolysis and attachment were shown to occur under a rapidly attained equilibrium, and a large excess of water (>32 equiv) is required to effect a practically quantitative release of boronic acids from DEAM-PS. Despite their relative sensitivity to water and alcohols, DEAM-PS-bound arylboronic acids functionalized with a formyl, a bromomethyl, a carboxyl, or an amino group can be transformed in good to excellent yields into a wide variety of amines, amides, anilides, and ureas, respectively. Ugi multicomponent reactions on DEAM-PS-supported aminobenzeneboronic acids, derivatization of multifunctional arylboronic acids, and sequential reactions can also be carried out efficiently. These new DEAM-PS-supported arylboronic acids can be employed directly into resin-to-resin transfer reactions (RRTR). This type of multiresin process helps eliminate time-consuming cleavage and transfer operations, thereby considerably simplifying the outlook of combinatorial library synthesis by manual or automated means. This concept was illustrated by a set of optimized procedures for the Suzuki cross-coupling and the borono-Mannich reactions.

Mizoroki-Heck type reaction of organoboron reagents with alkenes and alkynes. A Pd(II)-catalyzed pathway with Cu(OAc)2 as an oxidant.

[reaction: see text]. In contrast to the Pd(0)-catalyzed mechanism by Uemura, Mizoroki-Heck type reaction of boronic acids is found to proceed under a Pd(II)-mediated pathway using a catalytic amount of Pd(OAc)2 in the presence of Cu(OAc)2 as an oxidant. Treatment of a variety of alkenes with boronic acids, boronates, and sodium tetraphenylborate furnishes beta-arylated and alkenylated products in good to excellent yields. The reactions with norbornene, norbornadiene, and diphenylacetylene are also performed to give 1:2 or 2:1 coupling products.

Mechanistic study on the reaction of boronic acids with H-resorcinol

Kinetics for the reaction of m-nitrophenyl- ( m-NO 2Ph-), phenyl- (Ph-), methyl(Me-), and n-butyl- (n-Bu-) boronic acids with H-resorcinol has been studied at various temperatures and pressures. The pseudo first-order rate constant ( k obs) exhibited saturation in the plot of k obs against the total boronic acid concentration ( C B) for the reactions of m-NO 2PhB(OH) 2 and PhB(OH) 2, while the plot was linear for the reactions of MeB(OH) 2 and n-BuB(OH) 2, which leads to the following equations, respectively: k obs= k* KC B/(1+ KC B) and k obs= k* KC B= k f C B. It was experimentally shown that the reaction of boronic acids with H-resorcinol proceeds with rate determining second chelate-ring closure.

Synthesis of polybenzyls by Suzuki Pd-catalyzed crosscoupling of boronic acids and benzyl bromides: Model reactions and polyreactions

The palladium-catalyzed crosscoupling reaction of boronic acids and benzyl bromides can be used successfully for the preparation of benzyls in high yield. This C-C coupling reaction was optimized for the synthesis of polybenzyls by model reactions. Different reaction channels were observed here with meta- and para-bis(bromomethyl)benzenes. The main product with 1,3-bis(chloromethyl)benzene was the corresponding 1,3-dibenzylbenzene, but the main product with 1,4-bis(chloromethyl)benzene was the corresponding biaryl resulting from homocoupling of aromatic boronic acid. 1.3-Linked polybenzyls were synthesized based on the results of the model reactions. M̄n's of 2 380 corresponding to a DP of 26 were found based on GPC. No structural defects were detected within the limits of detection.

Synthesis of polybenzyls by Suzuki Pd-catalyzed crosscoupling of boronic acids and benzyl bromides: Model reactions and polyreactions

The palladium-catalyzed crosscoupling reaction of boronic acids and benzyl bromides can be used successfully for the preparation of benzyls in high yield. This C-C coupling reaction was optimized for the synthesis of polybenzyls by model reactions. Different reaction channels were observed here with meta- and para-bis(bromomethyl)benzenes. The main product with 1,3-bis(chloromethyl)benzene was the corresponding 1,3-dibenzylbenzene, but the main product with 1,4-bis(chloromethyl)benzene was the corresponding biaryl resulting from homocoupling of aromatic boronic acid. 1.3-Linked polybenzyls were synthesized based on the results of the model reactions. M̄n's of 2 380 corresponding to a DP of 26 were found based on GPC. No structural defects were detected within the limits of detection.