19813-76-4Relevant articles and documents
Cobalt-catalyzed C(sp2)?CN bond activation: Cross-electrophile coupling for biaryl formation and mechanistic insight
Dorval, Céline,Tricoire, Maxime,Begouin, Jeanne-Marie,Gandon, Vincent,Gosmini, Corinne
, p. 12819 - 12827 (2020/11/18)
Herein, we report a cross-electrophile coupling of benzonitrile derivatives and aryl halides with a simple cobalt-based catalytic system under mild conditions to form biaryl compounds. Even though the cobalt catalyst is able to activate the C(sp2)?CN bond alone, the use of the AlMe3 Lewis acid enhances the reactivity of benzonitriles and improves the cross-selectivity with barely any influence on the functional group compatibility. X-ray structure determination of an original low-valent cobalt species combined with catalytic and stoichiometric reactions reveals a catalytically active cobalt(I) species toward the aryl halide partner. On the other hand, experimental insights, including cyclic voltammetry experiments, suggest the involvement of a cobalt complex of a lower oxidation state to activate the benzonitrile derivative. Finally, density functional theory calculations support the proposed mechanistic cycle involving two low-valent cobalt species of different oxidation states to perform the reaction.
Photochemical arylation reactions by 4-chlorothioanisole
Lazzaroni, Simone,Dondi, Daniele,Fagnoni, Maurizio,Albini, Angelo
, p. 4360 - 4365 (2008/04/13)
The photochemistry of 4-chlorothioanisole (1) was investigated in various solvents, and it was found to involve the reduction to thioanisole as the main process. This occurs by heterolytic fragmentation of the triplet state of 1 and formation of the triplet 4-thiomethoxyphenylium ion, as supported by DFT calculations. The cation is trapped by alkenes and, less efficiently, by benzene, resulting in new examples of the recently emerging arylation reactions by SN1 substitution of phenyl halides. The products from alkenes involve the phenonium ion as a further intermediate. The product distribution differs from the analogous reactions via 4-methoxyphenylium for including a larger proportion of 4-(β-substituted alkyl)- rather than 4-allylthioanisoles derivatives in alcohols, for the lower fraction of rearranged α-substituted 4-alkyl-thioanisoles and for the formation of some 4-cyclopropylthioanisole with allyltrimethylsilane. The difference is accounted for by the more developed dipolar character of the C-C cyclopropane bonds in the intermediate phenonium, as indicated by DFT calculations. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Selective metal-halogen exchange of 4,4′-dibromobiphenyl mediated by lithium tributylmagnesiate
Dolman, Sarah J.,Gosselin, Francis,O'Shea, Paul D.,Davies, Ian W.
, p. 5092 - 5098 (2007/10/03)
A selective metal-halogen exchange/electrophilic quench protocol on 4,4′-dibromobiphenyl 4 that proceeds under non-cryogenic conditions is reported. This method provides an economic alternative to traditional transition-metal catalyzed cross-coupling chemistry to prepare various biaryls 7a-g. This novel route to functionalized biaryls was used as the basis for the kg-scale preparation of a biphenyl ketone 1, a key intermediate in the synthesis of a potent cathepsin K inhibitor.
