Selective Iron Catalyzed Synthesis of N‐Alkylated Indolines and Indoles

Abstract

Whereas iron catalysts usually promote catalyzed C3‐alkylation of indole derivatives via a borrowing‐hydrogen methodology using alcohols as the electrophilic partners, this contribution shows how to switch the selectivity towards N‐alkylation. Thus, starting from indoline derivatives, N‐alkylation was efficiently performed using a tricarbonyl(cyclopentadienone) iron complex as the catalyst in trifluoroethanol in the presence of alcohols leading to the corresponding N‐alkylated indoline derivatives in 31–99 % yields (28 examples). The one‐pot, two‐step strategy for the selective N‐alkylation of indolines is completed by an oxidation to give the corresponding N‐alkylated indoles in 31–90 % yields (15 examples). This unprecedented oxidation methodology involves an iron salt catalyst associated with (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and a stoichiometric amount of t‐BuOOH at room temperature.

Palladium-Catalyzed Reaction of Indolines with Dihydropyrroles: Access to N-Alkylated Indoles

“…reported Ru-catalyzed N-alkylation of indoles by using alcohols via the “borrowing hydrogen” methodology . N-Alkylated indoles can also be prepared from corresponding indolines. ,, The reaction process includes N-alkylation of indolines and subsequent oxidation or H 2 release under transition metal catalysis. For example, Rueping and co-workers reported pincer-manganese-catalyzed selective synthesis of C- and N-alkylated indoles from indolines and primary alcohols through a combined acceptorless dehydrogenation and hydrogen autotransfer strategy .…”

N-Alkylation of Amines by C1–C10 Aliphatic Alcohols Using A Well-Defined Ru(II)-Catalyst. A Metal–Ligand Cooperative Approach

“…Alcohols are sustainable, environmentally benign, inexpensive, and readily obtained from lignocellulose biomass. Using alcohol as the starting precursor in chemical reactions for synthesizing different functional molecules may curtail our dependence on fossil fuel resources, reducing CO 2 emission as well. − Carbon–nitrogen bond formation reaction using alcohol is a promising and nontoxic greener approach that avoids producing stoichiometric salt waste and hazardous side products . Transition metal-catalyzed C–N cross-coupling reactions with amines and alcohols proceed via a borrowing hydrogen transfer or hydrogen autotransfer mechanism in which the alcohols transform to carbonyls upon dehydrogenation followed by reductive amination .…”

Visible light-induced cascadeN-alkylation/amidation reaction of quinazolin-4(3H)-ones and related N-heterocycles

“…However, these oxidative amidation reactions always require a two-step procedure, including the quaternarization of isoquinolines with benzyl bromide 18 and the subsequent oxidation with different catalysts and oxidants. To date, only limited examples of cascade N -alkylation/amidation of isoquinoline derivatives have been reported.…”