Catalytic System for the Heck Reaction of Fluorinated Haloaryls

Abstract

A catalytic system for the Heck reaction of fluorinated haloaryls, which involves the first catalytic insertion into a metal−perfluoroaryl bond, has been developed. Pentafluorophenyl complexes of palladium which lack ligands other than halides are used as catalysts. The absence of other ligands besides solvent, halides, and substrates is required for an efficient functionalization. Pentafluoro- and tetrafluoro-substituted haloaryls can be efficiently reacted with terminal and disubstituted olefins, such as styrene, α-methylstyrene, and acrylate esters, but nonactivated alkenes give only moderate yields. Coordination−insertion is rate determining for pentafluoroaryl and tetrafluoroaryl bromides, which can be switched to oxidative addition if a large excess of olefin is used. Thus, the best reaction conditions can be reached by adjusting the actual ratio of haloaryl to olefin for each combination of substrates.

Pd-Catalyzed Mizoroki-Heck Reactions Using Fluorine-Containing Agents as the Cross-Coupling Partners

“…Electron-deficient olefins bearing ester, amide, phosphonate, or ketone groups worked well to give moderate to excellent yields and high stereoselectivities. Notably, nonactivated aliphatic olefins and electron-rich alkenes underwent smooth reactions in good yields, which were in sharp contrast to previous results [86,87]. In the case of polyfluoroarenes (157), the reactions using PivOH (1.2 equiv) instead of DMSO (5%) afforded alkenylated products (159) in moderate yields with moderate to good regioselectivities.…”

“…The Mizoroki-Heck couplings of bromide 83 with 1H,1H,2H-perfluoroalkenes (84) employed a palladacycle catalyst which proved to be a better catalyst than Pd(OAc) 2 . Hydrogenation of the coupled alkenes (85) followed by removal of the Boc groups gave secondary amines as fluorous tags for diazonium-substituted aryl iodides (87). The final stage of OPV tetramer growth was a Heck-type reaction with an end-capping styrene derivative (89).…”

“…Addition of NBu 4 Br to the latter reaction mixture could reactivate the process. It seemed that displacement of bromides on Pd(0) by alkene at high concentration severely slowed the oxidative addition, which became rate-determining instead of the coordination-insertion step [86,87]. Thus, the success of this catalysis required a compromise between the optimal conditions for the oxidative addition and the coordination-insertion.…”

Preparation of donor–acceptor substituted fluorostilbenes and crystal chemistry of fluorinated (E)-4-(4-halogeno-styryl)-benzonitriles

“…In contrast, the series X-C 6 H 4 -CH CH-C 6 F 4 -CN (22)(23)(24) showed a bathochromic shift (red shift) compared to the Hhomologues (16)(17)(18). This is due to the inversion of the charge distribution, which has been described in our previous work on the subject, calculated for the bromo derivatives [3].…”

“…Albeniz et al [22] observed that the reaction increases with higher concentration of styrene, favouring the oxidative addition process. However, a large excess can stop the reaction.…”