Transitions: The title reaction has been developed for the synthesis of a variety of tert-butyl benzoates by employing 1,10-phenanthroline as an additive. Various functional groups were tolerated and heteroaryl iodides were also suitable substrates. Preliminary mechanism studies were conducted and indicate the participation of radical intermediates.

Two at once: Xanthones with different functional groups were obtained with CO (balloon) in the presence of a simple catalytic system that consists of Pd(OAc)2, K2S2O8, and trifluoroacetic acid (see scheme). Preliminary mechanism studies reveal that the second CH functionalization might be the rate‐determining step.

Transition-metal-catalyzed carbonylation involving CO gas is a very important and fundamental chemical transformation, which not only extends the carbon chain length, but also introduces a synthetically versatile carbonyl group. Since the pioneering work of Heck and co-workers, [1,2] transition-metalcatalyzed alkoxycarbonylation of organic halides with CO to afford esters has shown synthetic potential, and been applied in some chemical syntheses during the past several decades (Scheme 1). [3][4][5][6][7] Besides, transition metals, especially palladium-and manganese-catalyzed radical alkoxycarbonylation of alkyl iodides under photoirradiation conditions have also been developed to be an efficient approach towards the synthesis of carboxylic acid esters. [8][9][10][11][12][13] However, there are still some challenges such as the turnover numbers and turnover frequencies, which hinder its wide industrial application. Generally, low-valent-metal catalysts such as palladium(0) are required to activate the CÀX bond, whereas the strong binding ability of CO towards low-valent metals deactivate the catalyst, which present a challenge in this transformation. Therefore, discovering a practical alternative to transitionmetal-catalyzed carbonylation and opening a new avenue for the carbonylation by utilizing CO gas is highly desirable.Transition-metal-free processes have recently attracted more and more attention from the synthetic community, and we thought that it might serve as an alternative route to addressing the above-mentioned challenge (Scheme 1). The key challenge of this idea is to determine how to activate CÀX without the help of transition-metal catalysts. Radical activation could be an option. Recently, transition-metal-free coupling reactions of aryl halides with arenes and alkenes have been developed, and the combination of MOtBu and bidentate nitrogen ligands was employed to initiate the aryl radical by single-electron transfer (SET). [14][15][16][17][18][19][20][21][22] Obviously, if aryl radicals were formed, the insertion of CO would produce the acyl radical and further generate a carboxylic derivative. Although known since the 1950s, [23] the potential of radical carbonylation in chemical synthesis has not received a great deal of attention, and in fact, only a few nice results have been reported to date. These results usually involve a xenon photolytic system or AIBN/tin hydride mediated radicalchain reaction employing alkyl iodides as substrates. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. Herein, we disclose a protocol for accessing tert-butyl benzoates through the transition-metal-free alkoxycarbonylation of aryl halides.Our experiment was initiated by treating 4-iodotoluene (1 a) with KOtBu in the presence of a high pressure CO (Table 1). By optimizing various reaction parameters, the best results were obtained with the combination of 40 mol % 1,10

Zwei auf einmal: Xanthone mit verschiedenen funktionellen Gruppen wurden mit CO (Ballon) in Gegenwart eines einfachen Katalysatorsystems bestehend aus Pd(OAc)2, K2S2O8 und Trifluoressigsäure erhalten (siehe Schema). Erste mechanistische Studien legen nahe, dass die zweite C‐H‐Funktionalisierung geschwindigkeitsbestimmend ist.

Palladium-Catalyzed Oxidative Double C-H Functionalization/Carbonylation for the Synthesis of Xanthones. -Xanthones with different functional groups (III) are obtained by reaction of diarylethers (I) with carbon monoxide in the presence of a simple catalytic system consisting of Pd(OAc)2, K2S2O8, and trifluoroacetic acid. The method is applicable to symmetrical as well as unsymmetrical diaryl ethers. -(ZHANG, H.; SHI, R.; GAN, P.; LIU, C.; DING, A.; WANG, Q.; LEI*, A.; Angew. Chem., Int. Ed. 51 (2012) 21, 5204-5207, http://dx.