@article {46415, title = {C-H functionalization of indoles by 3d transition-metal catalysis}, journal = {Asian Journal of Organic Chemistry}, year = {2019}, month = {DEC}, type = {Review; Early Access}, abstract = {

Over the past decade, the use of 3d transition metal for the regioselective C-H bond functionalization of indoles has significantly increased. Particularly, advances in manganese, iron, cobalt, nickel and copper catalysis have demonstrated the selective C(2)-H and C(3)-H arylation, alkenylation, alkynylation and alkylation to a greater extent. Similarly, the C-O and C-N bond-forming reactions are manifested via direct C-H bond activation by these earth-abundant metals. The emergence of 3d metals in selective functionalization of the biologically relevant indoles and related heteroarenes would make this protocol more attractive for practical applications. Herein, we provide a brief overview of 3d transition metal-catalyzed (mostly Mn, Fe, Co, Ni and Cu) C-H functionalization of indoles and related heteroarenes.

}, keywords = {3d transition metal, C-H functionalization, Indole, indoline}, issn = {2193-5807}, doi = {10.1002/ajoc.201900554}, author = {Jagtap, Rahul A. and Punji, Benudhar} } @article {46936, title = {Palladium-catalyzed oxidative annulation of pyrrolylalkyl-1H-azoles: towards the synthesis of polyheterocyclic arenes}, journal = {Synthesis-Stuttgart}, volume = {52}, year = {2020}, month = {MAR }, pages = {719-726}, type = {Article}, abstract = {

A highly efficient and regioselective palladium-catalyzed annulation protocol for a series of linear and terminally substituted 1,2- and 1,3-di(heteroaryl)alkanes to the corresponding polyheterocyclic arenes is reported. Herein, intramolecular oxidative coupling involving double C(sp(2))-H bond functionalization provides a feasible access to biheteroaryl systems annulated to a six-membered ring. The methodology is not restricted to six-membered annulations and was extended to the synthesis of compounds with a seven-membered ring and biheteroaryl core.

}, keywords = {C-H functionalization, imidazoles, oxidative coupling, Palladium, pyrroles}, issn = {0039-7881}, doi = {10.1055/s-0039-1691492}, author = {Tripathi, Krishna N. and Bansode, Avinash H. and Singh, Ravi P.} } @article {47412, title = {Nickel-catalyzed C-H bond functionalization of azoles and indoles}, journal = {Chemical Record}, volume = {21}, year = {2021}, month = {DEC}, pages = {3573-3588}, type = {Article}, abstract = {

Direct C-H functionalization of privileged and biologically relevant azoles and indoles represents an important chemical transformation in molecular science. Despite significant progress in the palladium-catalyzed regioselective C-H functionalization of azoles and indoles, the use of abundant and less expensive nickel catalyst is underdeveloped. In the recent past, the nickel-catalyzed regioselective C-H alkylation, arylation, alkenylation and alkynylation of azoles and indoles have been substantially explored, which can be applied to the complex organic molecule synthesis. In this Account, we summarize the developments in nickel-catalyzed regioselective functionalization of azoles and indoles with a considerable focus on the reaction mechanism.

}, keywords = {azoles, C-C Bond formation, C-H functionalization, indoles, Nickel}, issn = {1527-8999}, doi = {10.1002/tcr.202100113, Early Access Date = JUN 2021}, author = {Jagtap, Rahul A. and Punji, Benudhar} } @article {48729, title = {Enantioselective intramolecular decarboxylative C-H bond func-tionalization of quinazolinones with amino acids by visible light photoredox catalysis}, journal = {Chemistry-An Asian Journal}, volume = {18}, year = {2023}, month = {JUL}, type = {Article}, abstract = {

The direct visible light-mediated intramolecular decarboxylative C-H functionalization of Csp(2)-H bond adjacent to the nitrogen of a heteroarene has been achieved by iridium-catalyzed photodecarboxylative radical cyclization. This method offers rapid entry to the synthesis of quinazolinone scaffolds from easily accessible starting materials. The newly developed protocol is mild, operationally simple, oxidant free and general. The utility of this unique Csp(3)-Csp(2) bond forming reaction has been demonstrated in the syntheses of Circumdatin, Sclerotigenine and Benzomalvin A class of quinazolinone natural products and their congeners. The present work represents an interesting example of use of memory of chirality in decarboxylative C-C bond forming enantioselective photoredox reaction.

}, keywords = {C-H functionalization, memory of chirality, Minisci reaction, photodecarboxylative cyclization, photoredox catalysis, quinazolinone alkaloid, Radical}, issn = {1861-4728}, doi = {10.1002/asia.202300235}, author = {Sonavane, Sameer R. and Mhaske, Santosh B.} } @article {48285, title = {Late-stage C(sp(2))-H arylation of artemisinic acid and arteannuin B: effect of olefin migration towards synthesis of C-13 arylated artemisinin derivatives}, journal = {Chemistry-An Asian Journal}, volume = {18}, year = {2023}, month = {APR }, type = {Article}, abstract = {

In recent years, C-H bond functionalization has emerged as a pivotal tool for late-stage functionalization of complex natural products for the synthesis of potent biologically active derivatives. Artemisinin and its C-12 functionalized semi-synthetic derivatives are well-known clinically used anti-malarial drugs due to the presence of the essential 1,2,4-trioxane pharmacophore. However, in the wake of parasite developing resistance against artemisinin-based drugs, we conceptualized the synthesis of C-13 functionalized artemisinin derivatives as new antimalarials. In this regard, we envisaged that artemisinic acid could be a suitable precursor for the synthesis of C-13 functionalized artemisinin derivatives. Herein, we report C-13 arylation of artemisinic acid, a sesquiterpene acid and our attempts towards synthesis of C-13 arylated artemisinin derivatives. However, all our efforts resulted in the formation of a novel ring-contracted rearranged product. Additionally, we have extended our developed protocol for C-13 arylation of arteannuin B, a sesquiterpene lactone epoxide considered to be the biogenetic precursor of artemisinic acid. Indeed, the synthesis of C-13 arylated arteannuin B renders our developed protocol to be effective in sesquiterpene lactone as well.

}, keywords = {Arteannuin B, Artemisinic acid, artemisinin, C-H functionalization, Pd-catalysis}, issn = {1861-4728}, doi = {10.1002/asia.202300162}, author = {Paul, Sayantan and Ghodake, Balaji M. M. and Bhattacharya, Asish K. K.} }