@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 {49015, title = {Ligand-free MnBr2-catalyzed chemo- and stereoselective hydroboration of terminal alkynes}, journal = {Chemistry-an asian jounrnal}, volume = {19}, year = {2024}, month = {MAY}, type = {Article}, abstract = {

Developing simple and benign protocols for synthesizing alkenylboronates is crucial as they are synthetically valuable compounds in various organic transformations. In this work, we report a straightforward ligand-free protocol for synthesizing alkenylboronates via atom-economical hydroboration of alkynes with HBpin catalyzed by a manganese salt. The reaction shows a high level of chemo and regioselectivity for the terminal alkynes and exclusively produces E-selective alkenylboronates. The hydroboration scope is vast, with the resilience of a range of synthetically beneficial functionalities, such as halides, ether, alkenyl, silyl and thiophenyl groups. This reaction proceeds through the involvement of a metal-hydride intermediate. The developed alkenylboronate can be smoothly converted to useful C-C, C-N and C-I bond-forming reactions.

}, keywords = {alkenylboronates, alkyne, Hydroboration, manganese, stereoselectivity}, issn = {1861-4728}, doi = {10.1002/asia.202400158}, author = {Pawar, Rameshwar B. and Karmur, Mital H. and Punji, Benudhar} } @article {49322, title = {Manganese-catalyzed chemoselective direct hydrogenation of α,β-epoxy ketones and α-ketoamides at room temperature}, journal = {Advanced Synthesis \& Catalysis}, volume = {366}, year = {2024}, month = {AUG}, pages = {3338-3345}, type = {Article}, abstract = {

Chemoselective hydrogenation of alpha,beta-epoxy ketones and alpha-ketoamides is achieved at room temperature (25 degrees C) using 2.0 bar H-2 and a pincer-ligated Mn(I) catalyst that provides synthetically valuable alpha-hydroxy epoxides and alpha-hydroxy amides. This protocol applies to a wide range of alkyl- and aryl-substituted alpha,beta-epoxy ketones, including terpenes (alpha-ionone, nootkatone, and R-carvone)- and steroids (testosterone and progesterone)-derived epoxy ketones, and tolerates H-2 sensitive functionalities, such as halides, acetyl, nitrile, nitro, epoxide, alkenyl and alkynyl groups. Additionally, alpha-ketoamides bearing reducible functional groups, including acetyl and diazo benzene, were untouched under this protocol and selectively converted to alpha-hydroxy amides. A preliminary mechanistic study highlighted the metal-ligand cooperative H-2 activation process.

}, keywords = {alpha, beta-epoxy ketones, chemoselectivity, direct hydrogenation, manganese, Metal-ligand cooperation}, issn = {1615-4150}, doi = {10.1002/adsc.202400267}, author = {Shabade, Anand B. and Singh, Rahul K. and Gonnade, Rajesh G. and Punji, Benudhar} }