Palladium-catalyzed non-directed C–H bond arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole

Abstract

International audienceWe report, herein, on palladium-catalyzed direct arylation of difluorobenzenes and dichlorobenzenes bearing benzoxazole or benzothiazole moieties, which don't act as directing groups. With moderate electron-withdrawing substituents on the aryl bromides as coupling partners, the reaction proceeds nicely using phosphine-free PdCl2 catalyst, and potassium pivalate/dimethylacetamide (PivOK/DMA) as catalytic system. The reaction was regioselective and occurred at the less hindered ortho-positions of fluorine or chlorine atom

Benzimidazole bearing Pd–PEPPSI complexes catalyzed direct C2‐arylation/heteroarylation ofN‐substituted benzimidazoles

“…using palladium catalyst. [30] In a similar vein, a test for extended arylation and regioselectivity on 1-benzyl-2-[5-bis(trifluoromethyl)phenyl]-1H-benzo[d]imidazole 8d was practiced with 4-bromoanisole but no conversion of the starting material was observed, possibly owing to the suppression of reactivity by the electronic properties of -CF 3 groups present on either side of the active -CH carbon. Instead, Pd-PEPPSI-3 catalyzed homocoupling of bromoanisole yielded 8aa (Scheme 6).…”

Palladium-Catalyzed Regioselective C–H Bond Arylations of Benzoxazoles and Benzothiazoles at the C7 Position

“…Recently, we reported the palladium-catalyzed direct arylation of benzoxazole or benzothiazole derivatives, in which such functional groups had not displayed any ortho -directing effect . In the course of our investigation on the reactivity of 2-arylbenzoxazole, we also employed 2-phenylbenzoxazole as starting material using our previous optimized reaction conditions (i.e., Pd­(OAc) 2 , 2 eq.…”

Pd-Catalyzed and Copper Assisted Regioselective Sequential C2 and C7 Arylation of Thiazolo[5,4-f]quinazolin-9(8H)-one with Aryl Halides

“…In addition, compounds 4 are especially difficult to purify owing to their low solubility. It was noted that the arylation of the 2-arylbenzothiazole moiety of compounds 2b – f that afforded an undesired product was not observed . The stepwise Pd-catalyzed C–H arylation of thiazolo­[5,4- f ]­quinazolin-9­(8 H )-one 1 with aryl bromides and iodides occurs in an efficient manner with broad tolerance to substituents on the coupling partners.…”

“…It was noted that the arylation of the 2-arylbenzothiazole moiety of compounds 2b−f that afforded an undesired product was not observed. 13 The stepwise Pd-catalyzed C−H arylation of thiazolo[5,4-f ]quinazolin-9(8H)-one 1 with aryl bromides and iodides occurs in an efficient manner with broad tolerance to substituents on the coupling partners. The challenging removal of the protecting group was investigated, but many of the standard debenzylation strategies failed.…”