Synthesis in the Key of Catellani: Norbornene-Mediated ortho C–H Functionalization

Palladium-Catalyzed Regioselective 2-Carbethoxyethylation of 1H– Indoles By C-H Activation: One-Step Synthesis of Ethyl 2-(1H-Indol-2-Yl) Acetates

“…The Catellani reaction, a palladium-catalyzed norbornenemediated cascade reaction, has been modified to achieve the direct functionalization of indoles [53][54][55]. Recently, Bressy et al reported an intramolecular direct arylation of indoles based on modified Catellani conditions [56].…”

Bibliographical Background: The Ortho Effect in The Catellani Reaction

“…In 1985, she published the synthesis of dihydrophenanthrene 1 by coupling of two molecules of bromobenzene and one of norbornene, through the proposed formation of palladacycle 2 ( Fig. 7.1) [4].Since then, numerous applications of palladium/norbornene-mediated domino processes have been reported, allowing the synthesis of various polycyclic frameworks and the construction of up to three carbon-carbon bonds in a single reaction [5][6][7]. The catalytic cycle of the Catellani reaction, involving multiple oxidation state of palladium (0, II and potentially IV), will be presented first.…”

Palladium-Catalyzed Double C–H Functionalization of Arenes at the Positions <i>ortho</i> and <i>meta</i> to Their Directing Group: Concise Synthesis of Benzocyclobutenes

“…The reaction of the ortho-deuterated substrate 1e-d 3 38) under the optimized conditions gave a KIE value 1.4, which was estimated from a ratio of the products (a). In contrast, the meta-deuterated substrate 1e-d 6 showed a KIE value of 2.3 (b). These results indicated that the cleavage of the C-H bond at the meta position required a larger activation energy rather than that of the ortho position.…”

“…Two major routes have been developed for the multiple functionalization of arenes in this way, including (i) the reaction of benzyne intermediates [1][2][3][4] and (ii) the norbornenemediated ortho C-H functionalization of arenes. [5][6][7] Benzyne is a highly reactive species because of its strained structure, making it a useful intermediate for the transformation of aromatic rings through cycloaddition and multicomponent reactions. [1][2][3][4] Regarding the ortho C-H functionalization of arenes, various norbornene-mediated strategies have been developed for the ipso and ortho functionalization of aryl halides using palladium catalysts, including those reported by Catellani et al, 8,9) Lautens and colleagues, [10][11][12] Malacria and colleagues, 13) Dong Z. and Dong G., 14) Liang and colleagues, 15) Ritter and colleagues 16) and Zhou and colleagues.…”