Heck reaction with arylboronic acids

Odell L.R., Lindh J., Gustafsson T., Larhed M. Continuous flow palladium(II)-catalyzed oxidative Heck reactions with arylboronic acids. Eur. J. Org. Chem. 2010 (12) 2270-2274. 

Alkenyl, Alkynyl, Aryl and Heteroaryl Acids. Treatment of readily accessible (E)- and (Z)-alkyl and aryl substituted vinyl boronates (196) with triethyl phosphite in the presence of lead diacetate results in their stereospecific transformation into (E)- and (Z)-vinylphosphonates (197) (Scheme 53). ° Palladium acetate catalysed Mizoroki-Heck reaction of arylboronic acids (198) with diethyl vinylphosphonates (199) is an effective synthetic approach to... 

Halopyridines or pyridinyl triflates take part in palladium-catalysed reactions -Heck, carbonylation, and coupling reactions, for example with alkynes, or in Suzuki reactions with arylboronic acids,and cyclopropylboronic acids. 

Reddy and collaborators reported a new one-pot, three-component procedure toward the synthesis of novel 4-phenyl-2-[3-(alkynyl/alkenyl/aryl) phenyl] pyrimidine libraries starting with the Michael addition of enaminone 64 with 3-bromobenzimidamide hydrochloride (65) (Scheme 28) (13S75). This was followed by a cyclization, an isomerization, a dehydration, and a subsequent Sonogashira reaction with terminal alkynes or a Suzuki reaction with arylboronic acids or a Heck coupling reaction with alkenes. 

The same authors also used ESI-MS/MS to study an air-promoted oxidative Heck reaction between arylboronic acids and enamides as electron-rich olefins (Scheme 7.13) [29]. In addition to the conventional Mizoroki-Heck reaction of unsaturated compounds with organic halides or triflates as electrophiles, the use of nucleophilic organometallic reagents, such as organoboron compounds, has... 

Oxidative Heck arylation of enamides with arylboronic acids, using oxygen gas as a reoxidant for Pd(0) and 2,9-dimethyl-1,10-phenanthroline as a chelating regiocontrolling ligand, yielded a (= internally) arylated reaction product as the major compound with a very good a//3 selectivity [92]. Microwave irradiation with prepressurized sealed vials proved useful in reducing the reaction time (Scheme 82). 

Figure 26 Plausible Mizoroki-Heck type reaction pathway with arylboronic acid.

Palladacycles prepared by the addition of furancarbothioamide to a methanol solution of Li2PdCl4 at room temperature are soluble in hexane, chloroform, and moderately soluble in polar solvents DMF and DMSO [187]. These palladacycles are thermally stable, not sensitive to air or moisture, and can be applied effectively in the Heck reaction of aryl halides with terminal olefins and in the Suzuki reaction of aryl halides with arylboronic acids. These reactions were performed under aerobic conditions, leading to turnover numbers... 

Palladium-catalyzed reactions such as Suzuki, Heck, Trost-Tsuji and Stille have been modified in the presence of KF/A1203 without solvent under microwave irradiation conditions by Villemin et al. [10], These reactions rapidly afforded the product in moderate to excellent yields. For instance, a reaction of iodobenzene with arylboronic acids was completed in 2-15 min. Recently, improved methods under microwave irradiation have been reported [11-16] (Scheme 5.5). 

Zou, G., Wang, Z., Zhu, J. and Tang, J. (2003) Rhodium-catalyzed Heck-type reaction of arylboronic acids with a,/3-unsaturated esters tuning /3-hydrogen elimination versus hydrolysis of alkylrhodium species. Chem. Commun., 2438-9. 

A palladium(II)-catalysed Heck-Mizoroki/Suzuki-Miyaura domino reaction of arylboronic acids with vinyl ethers (34), catalysed by (CF3C02)2Pd and using p-benzoquinone (p-BQ) as reoxidant, has been developed. The key importance of the... 

The study started by selecting an oxidative Heck coupling between arylboronic acid Sc, enamide 36a, and 2,9-dimethyl-l,10-phenanthroline (38) as the ligand. The aliquots were taken from the reaction mixture after 3 h at room temperature and diluted with acetonitrile in a 1 10 ratio before being injected into the mass spectrometer. Table 7.8, showing the detected organopalladium intermediates found in this study, supports the typically catalytic cycle of an oxidative Heck reaction. Entry 1 shows all the intermediates observed during the whole process. 

The oxidative Heck-Mizoroki reaction has also been adapted to flow-chemistry systems. Lahred and coworkers have used this procedure to couple -butyl acrylate and -butyl vinyl ether with arylboronic acids using Pd(OAc)2 with />-benzoquinone as the oxidant [88]. The yields were generally good (56-85%). 

With a,p-unsaturated esters, a similar rhodium-catalyzed Heck-type reaction of arylboronic acids was reported by Zou et al. [33]. t-Butyl acrylate (46a) reacted with phenylboronic acid (2m) in the presence of the RhCl3(H20)3, which is a rhodium precursor of choice, and PPh3 in a 3 1 toluene-water mixture at 100 °C for 20 h to give a 83% yield of trons-cinnamate (47am) (Scheme 4.19). The reaction of methyl acrylate... 

Arylboronic acids engage in Heck reactions with vinyl sulfones and phosphonates to give the corresponding fi-arylated a,/3-unsaturated sulfones and phosphonates, respectively (eq... 

Because many 4-benzylpiperidines are physiologically and pharmacologically active, an efficient route to these compounds was developed <03TL8249>. Cyclization of imines containing an allylsilane with aldehydes in a one-pot reaction resulted in 4-methylenepiperidines in good yields. Heck-type arylation of arylboronic acids with 4-methylenepiperidines afforded the styryl derivatives, which gave the desired piperidines on reduction. 

Aryl diazonium salts can be used coupled with alkenes in a Heck-Uke reaction (12-15)7 Other reactive aryl species also couple with aryldiazonium salts in the presence of a palladium catalyst7 A Suzuki type coupling (13-9) has also been reported using arylboronic acids, aryldiazonium salts and a palladium catalyst/ ... 

Alkylation. Acetals of enals serve as alkylating agents for t-butyl (3-keto esters using a Pd complex of BINAP. With a cationic Pd complex of (R)-BINAP intramolecular addition of arylboronic acid moiety to a sidechain ketone leads to chiral, tertiary henzylic alcohols. Heck reaction. Cyclization with desymmetrization is shown to proceed in excellent yields and ee by the formation of tetralin derivatives. ... 

Closely related to Heck coupling, the Suzuki cross-coupling reaction (the coupling reaction of a halogenoarene with an arylboronic acid or ester) [218] has also been successfully performed in ionic liquids. Welton et al. used Pd(PPh3)4 as catalyst in [BMIM][BF4] to convert bromo- and iodoarenes vnth phenylboronic acid... 

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