An Aryl to Imidoyl Palladium Migration Process Involving Intramolecular C−H Activation

Abstract

Biologically interesting fluoren-9-one and xanthen-9-one derivatives have been prepared by a novel aryl to imidoyl palladium migration, followed by intramolecular arylation. The fluoren-9-one synthesis appears to involve both a palladium migration mechanism and a C-H activation process proceeding through an unprecedented organopalladium(IV) hydride intermediate. The results from deuterium labeling experiments are consistent with the proposed dual mechanism.

Scandium triflate-catalyzed one-pot domino approach towards general and efficient syntheses of unsymmetrical 9-substituted xanthene derivatives

“…While investigating the mechanism for the above one-pot strategy, we came across Li et al's report 17 in which they mention that a 9-arylxanthene derivative could be formed through an intermediate triarylmethane (TRAM) derivative. 11 We also isolated one of the intermediates (14c), which, on treatment with 5 mol% of Sc(OTf) 3 in dry DCM at rt under normal atmospheric conditions, was converted to 12c (Scheme 3), confirming the hypothesis that C-C bond cleavage might be taking place first, followed by the intramolecular Friedel-Crafts reaction, to provide the desired cyclized product 12c. It was assumed that Sc(OTf) 3 , as an electrophile, associates at the 3-position of the indole (15c), and the required push from the oxygen of OAr 1 leads to cleavage of the strong C-C bond, resulting in a stabilized carboxonium ion intermediate (16c).…”

Renaissance of Organic Synthesis Using Isocyanides

“…The feasibility of the hypothesis was supported, in part, by Larock's report that imidoyl palladium that is generated from iodide J by unique aryl-to-imidoyl palladium migration can undergo similar cyclization to afford imine I (Scheme 7c). 35 To our delight, the desired cyclocoupling of 2-halobiphenyl and isocyanide proceeded under conditions almost identical to those of Larock's cyclocarbonylation (eq 10). 36 A minor difference from Larock's conditions was the effect of the ligand: PPh 3 , in place of bulky electron-rich PCy 3 , promoted the reaction effectively.…”

Synthesis of 4H‐indeno[1,2‐b]thiophenes, 8H‐indeno[2,1‐b]‐thiophenes and 8H‐indeno[2,1‐b]furans having acrylic acid unit

“…The known 2-(thiophen-2-yl)benzaldehyde (1a) [17], 2-(thiophen-3-yl)benzaldehyde (1b) [18], 2-(furan-3-yl)benz-aldehyde (1c) [19] and 2-(pyridin-4-yl)benzaldehyde (1d) [20] were prepared from commercially available 2-formylphenyl-boronic acid with 2-bromo-, 3-bromothiophene, 3-bromofuran and 4-bromopyridine by Suzuki reaction according to the literature procedure.…”