A convenient enantioselective synthesis of 3-asymmetrically substituted oxindoles as progesterone receptor antagonists

Enantioselective Construction of Oxindoles Bearing a Quaternary Carbon via Ni-Al Bimetal-Catalyzed Formyl C-H Alkylation

Enantioselective transition metal-catalyzed C-H alkylation emerges as one of the most atom- and step-economical routes to chiral quaternary carbons, while big challenges still remain with acyl C-H alkylations. Herein, we use a Ni-Al bimetallic catalyst to facilitate a highly regioselective and highly enantioselective C-H alkylation of formamides with alkenes, constructing various oxindoles bearing a chiral quaternary carbon in up to 94 % yield and up to 95 % ee.

Synthesis of Unsymmetrical 3,3'-Dialkyloxindole Boronic Esters from 3-Alkylidene-2-oxindoles Enabled by Copper Catalysis

We describe a 1,2-alkylboration of 3-alkylidene-2-oxindoles with a diboron reagent and alkyl bromides and iodides enabled by copper/bisphosphine catalysis. This scalable alkylboration method provides facile access to 3,3'-dialkyloxindole boronic esters featuring an all-carbon quaternary stereocenter and an increased F(sp3) fraction. In addition to good functional group tolerance and prolific utilization of drug/pesticide-derived alkyl iodides, the conversion of the C-B bond to a C-C/C-X bond offers further opportunities for structural variation of 3,3'-dialkyloxindoles.

Photoinduced Alkyl/Aryl Radical Cascade for the Synthesis of Quaternary CF3-Containing Oxindoles and Indoline Alkaloids

Metal- and additive-free, photoinduced decarboxylative radical alkylation-cyclization of CF₃-acrylamides with alkyl redox-active esters provided the corresponding quaternary CF₃-oxindole derivatives in good yields. Notably, diaryliodonium salts also efficiently participated in the arylation-cyclization of CF₃-acrylamides in environmentally benign H₂O as a solvent. The present approach has been extended for the concise synthesis of CF₃-attached indoline alkaloid analogues, i.e., CF₃-(±)-desoxyeseroline, CF₃-(±)-esermethole, and CF₃-(±) progesterone receptor antagonists. The preliminary mechanistic studies revealed that the reaction is likely to proceed through initial photoexcitation of redox-active ester/diaryliodonium salts followed by the SET process with acrylamide.

A tethering directing group strategy for ruthenium-catalyzed intramolecular alkene hydroarylation

We report a new catalyst design for N-heterocycle synthesis that utilizes an alkene-tethered amide moiety as a directing group for aromatic C-H activation. This tethering directing group strategy is demonstrated in a ruthenium-catalyzed intramolecular alkene hydroarylation with N-aryl acrylamides to form oxindole products.

The carbomethylation of arylacrylamides leading to 3-ethyl-3-substituted indolin-2-one by cascade radical addition/cyclization

An FeCl2-promoted carbomethylation of arylacrylamides by di-tert-butyl peroxide (DTBP) is achieved, leading to 3-ethyl-3-substituted indolin-2-one in high yield. The reaction tolerates a series of functional groups, such as cyano, nitro, ethyloxy carbonyl, bromo, chloro, and trifluoromethyl groups. The radical methylation and arylation of the alkenyl group are involved in this reaction.