@article {46798, title = {Iron-catalyzed C(sp(2))-H alkylation of indolines and benzo[h]quinoline with unactivated alkyl chlorides through chelation assistance}, journal = {ACS Catalysis}, volume = {10}, year = {2020}, month = {JUL }, pages = {7312-7321}, type = {Article}, abstract = {

Regioselective C-H bond alkylation of indolines and benzo[h]quinoline with a wide range of unactivated and highly demanded primary and secondary alkyl chlorides is accomplished using a low-cost iron catalyst. This reaction tolerates diverse functionalities, such as C(sp(2))-Cl, fluoro, alkenyl, silyl, ether, thioether, pyrrolyl, and carbazolyl groups including cyclic and acyclic alkyls as well as alkyl-bearing fatty-alcohol and polycyclic-steroid moieties. The demonstrated iron-catalyzed protocol proceeded via either a five-membered or a six-membered metallacycle. Intriguingly, the C-7-alkylated indolines can be readily functionalized into free-NH indolines/indoles and tryptamine derivatives. A detailed mechanistic investigation highlights the participation of an active Fe(I) catalyst and the involvement of a halogen-atom transfer process via a single-electron-based mechanism. Deuterium labeling and kinetics analysis indicate that the C-H metalation of indoline is the probable turnover-limiting step. Overall, the experimental and theoretical studies supported an Fe(I)/Fe(III) pathway for the alkylation reaction comprising the two-step, one-electron oxidative addition of alkyl chloride.

}, keywords = {alkyl chlorides, Alkylation, C-H activation, chelation assistance, indolines, iron}, issn = {2155-5435}, doi = {10.1021/acscatal.0c02030}, author = {Jagtap, Rahul A. and Samal, Pragnya Paramita and Vinod, C. P. and Krishnamurty, Sailaja and Punji, Benudhar} } @article {47036, title = {Unactivated alkyl halides in transition-metal-catalyzed C-H bond alkylation}, journal = {ACS Catalysis}, volume = {11}, year = {2021}, month = {MAR }, pages = {3268-3292}, type = {Review}, abstract = {

Alkylation represents an important organic transformation in molecular science to develop privileged alkylated arenes and heteroarenes. Especially, the direct C-H bond alkylation using unactivated alkyl halides is a straightforward and attractive approach from both the step-economy and chemoselectivity perspectives. Substantial progress has been made in the direct alkylation using primary, secondary, and tertiary alkyl halides along with the methylation and fluoroalkylation. This Review broadly summarizes the transition-metal-catalyzed alkylations of C-H bonds on various arenes and heteroarenes with unactivated alkyl halides until October 2020. On the basis of the substrates utilized for alkylation, the Review is divided into two major sections: alkylation of arenes and alkylation of heteroarenes.

}, keywords = {(hetero)arenes, Alkylation, C-H activation, transition metals, unactivated alkyl halides}, issn = {2155-5435}, doi = {10.1021/acscatal.0c05580}, author = {Ankade, Shidheshwar B. and Shabade, Anand B. and Soni, Vineeta 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} }