We describe a general approach for the synthesis of allylated and benzylated pyrazoles. An electron-withdrawing substituent, such as nitro, chloro, and ester groups, at C4 renders the Lewis basic nitrogen atom to be less basic and the C-H bond more acidic than the ones of the parent ring, enabling Pd-catalyzed C-H allylation and benzylation reactions of pyrazoles. The new method expanding the scope of the C-H functionalization of pyrazoles beyond arylation reactions provides a rapid access to complex pyrazole compounds.

As trategy in whichc omplementary species are paired for the preparation of a-heteroaryl esters and amides from heteroarenes was developed. Readily available a-haloacetates and a-acetamides providedt he requisitea cetate and acetamide groups via three distinctive reactive species, namely nucleophilic carbanions, alkylpalladium complexes, and photoredox-generated electrophilic radicals. Based on their electronic properties, these intermediates were matched with variousf ive-membered heteroarenes, such as pyrazoles, imidazoles, thiophenes,f urans, pyrroles, and indoles. These flexible protocols offer easy access to a-heteroaryl acetic acid derivatives and expand the scope of heteroarenes that can be utilized forC ÀHa lkylation.

A palladium-catalyzed C-H arylation reaction of nitroimidazoles and nitropyrazoles was developed using aryl bromides as arene donors. The electron-withdrawing effect of the nitro group allows for direct C-H arylation reactions of the nitro diazoles with high regioselectivity under mild conditions. The new C-H arylation approach is thus complementary to nucleophilic substitution reactions, enabling the preparation of complex nitroazole compounds.

Catalytic C-H Allylation and Benzylation of Pyrazoles. -A new strategy for the preparation of C5-allyl and benzyl pyrazoles is developed. In the present allylation and benzylation reactions, an overalkylation and alkene isomerization of the products are suppressed. The reactions can be carried out under practical laboratory conditions without operational difficulties involving the handling of air-and moisture-sensitive reagents and special equipment to procure cryogenic conditions. The new method can also be applied to nitroimidazoles (IX). -(BAE, S.; JANG, H.-L.; JUNG, H.; JOO*, J. M.; J. Org. Chem. 80 (2015) 1, 690-697, http://dx.

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