C−H Activation and Palladium Migration within Biaryls under Heck Reaction Conditions

Abstract

[reaction: see text] Biaryl bromides such as 1 (R=NO(2), H, OMe) undergo the Heck reaction to give both the expected products 3 ("retention") as well as "crossover" products 4 derived from a migration of Pd and net transfer of reactivity from one aryl ring to the other. Under the conditions used, crossover is increasingly favored when electron-deficient arenes are involved. Crossover products derived from transfer onto the pyridine ring have also been observed.

Catalytic C–C coupling through C–H arylation of arenes or heteroarenes

“…According to Gallagher [132] and Larock [133] Pd migrates along arene or heteroarene nuclei and the corresponding complexes react with ethyl acrylate to give the respective isomers. Recently the isomeric Pd intermediates have been trapped by Suzuki cross-coupling using arylboronic acids (Scheme 44) [134].…”

Palladium-Catalyzed Intra- and Intermolecular C–H Arylation Using Mesylates: Synthetic Scope and Mechanistic Studies

“…As such, we explored the arylation of the amine substrate 27 - OMs bearing two electronically differentiated aryl rings that could undergo C–H functionalization. 19 As illustrated in Scheme 5, the reaction of 27 - OMs proceeded to afford a mixture of carbazoles 27a and 27b in a 3.9:1 ratio. The modest selectivity for the arylation of the electron-rich aryl rings is similar to that observed with Pd-catalyzed arylation using aryl halides 11a and tosylates 9 involving a CMD electrophilic palladation step.…”

Novel Aryne Chemistry in Organic Synthesis

“…25 Mukonine has been synthesized by several different methods. 3,26 By employing our procedure, mukonine can be obtained in a 76%…”

“…The optimal reaction conditions thus far developed employ 0.25 mmol of aniline, 1.1 equiv of silylaryl triflate 1a and 2.0 equiv of CsF in MeCN at room temperature for 10 h. Diphenylamine was obtained in a 92% yield (Scheme 1) ( We next studied the scope of this methodology by allowing a wide variety of aromatic amines to react with the silylaryl triflates 1a, 1b, and 1c. 26 The results are summarized in Table 1. Aniline itself and aniline with electron-donating and -withdrawing groups (Table 1, entries 1 and 3-8), such as nitro, cyano, ester, ketone, amide and methoxy groups, all react well with silylaryl triflate 1a and CsF to afford excellent yields of the desired phenyl-substituted products.…”