@article {46818, title = {MnBr2-catalyzed direct and site-selective alkylation of indoles and benzo[h]quinoline}, journal = {Organic Letters}, volume = {22}, year = {2020}, month = {JUN}, pages = {4643-4647}, type = {Article}, abstract = {

Manganese-catalyzed regioselective C-H alkylation of indoles and benzo[h]quinoline with a variety of unactivated alkyl iodides is reported. Unlike other Mn-catalyzed C-H functionalization, this protocol does not require a Grignard reagent base and employs a simple and inexpensive MnBr2 as a catalyst. This method tolerates diverse functionalities, including fluoro, chloro, bromo, iodo, alkenyl, alkynyl, pyrrolyl, and carbazolyl groups. The alkylation proceeds through a single-electron transfer pathway comprising reversible C-H manganesation and involving an alkyl radical intermediate.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.0c01398}, author = {Jagtap, Rahul A. and Verma, Suryadev K. and Punji, Benudhar} } @article {47999, title = {Manganese-catalyzed C(sp(2))-H alkylation of indolines and arenes with unactivated alkyl bromides}, journal = {Chemistry-an Asian Journal}, volume = {17}, year = {2022}, month = {MAY}, pages = {e202200103}, type = {Article}, abstract = {

Selective C(sp(2))-H bond alkylation of indoline, carbazole and (2-pyridinyl)arenes with unactivated alkyl bromides is achieved using MnBr2 catalyst in the absence of an external ligand. The alkylation uses a simple LiHMDS base and avoids the necessity of Grignard reagent, unlike other Mn-catalyzed C-H functionalization. This reaction proceeded either through a five- or a less-favored six-membered metallacycle, and tolerated diverse functionalities, including alkenyl, alkynyl, silyl, aryl ether, pyrrolyl, indolyl, carbazolyl and alkyl bearing fatty alcohol and polycyclic-steroid moieties. Alkylation follows a single electron transfer (SET) pathway involving 1e oxidative addition of alkyl bromide and a rate-limiting C-H metalation.

}, keywords = {Alkylation, C-H activation, indoline, ligand-free, manganese}, issn = {1861-4728}, doi = {10.1002/asia.202200103}, author = {Verma, Suryadev K. and Punji, Benudhar} } @article {49032, title = {Copper-catalyzed regioselective C-H alkylation of phenol derivatives with unactivated alkyl chlorides: manifesting a Cu(I)/Cu(III) pathway}, journal = {Journal of Catalysis }, volume = {430}, year = {2024}, month = {FEB}, type = {Article}, abstract = {

The use of unactivated alkyl chlorides in regioselective C -H alkylation is a highly challenging process with diverse applications of alkylation strategy in drug discovery and agrochemistry. In this work, we report an efficient and cost-effective copper -catalyzed protocol for the coupling of unactivated alkyl chlorides with the C -H bond of phenol derivatives via 2-pyridinyl chelation assistance. The reaction shows a high level of regioselectivity, leading to an exclusive ortho alkylation and providing a broad scope with the endurance of numerous functionalities such as silyl, ether, thioether, pyrrolyl, indolyl, carbazolyl groups, including alkyl bearing fatty alcohol, nonylphenol, and vitamin E. Detailed mechanistic investigations suggest that the alkylation occurs through a two -electron oxidative addition of alkyl chloride to an active Cu(I) species. Deuterium labeling and kinetics experiments indicate a facile and reversible C -H bond activation process. Overall, the alkylation follows a Cu(I)/Cu(III) pathway involving chelation-assisted smooth C -H metalation and rate -limiting C-Cl oxidative addition of alkyl chloride.

}, issn = {0021-9517}, doi = {10.1016/j.jcat.2024.115351}, author = {Verma, Suryadev K. and Punji, Benudhar} }