Synthesis of 2-(2-nitrophenyl)indoline-3-acetic acid derivatives via base-catalyzed cyclization of N-(2-nitrobenzyl)-2-aminocinnamic acid derivatives.

A protocol for the synthesis of 2-(2-nitrophenyl)indoline-3-acetic acid derivatives was developed via base-catalyzed cyclization of N-(2-nitrobenzyl)-2-aminocinnamic acid derivatives. The synthetic utility of this methodology was illustrated by the concise synthesis of dihydropaullone, a partially saturated analog of paullone. Furthermore, the indoline scaffold could be further converted to the corresponding indoles and other indole-fused heterocycles.

A cyanide-catalyzed imino-Stetter reaction enables the concise total syntheses of rucaparib.

Two routes toward the synthesis of rucaparib, an FDA-approved drug used for the treatment of ovarian and prostate cancers, have been developed from commercially available starting materials utilizing the cyanide-catalyzed imino-Stetter reaction as the key step for the construction of the indole motif bearing all the desired substituents in their correct positions. In the first-generation synthesis, meta-fluorobenzoate, the starting material currently used in the process chemistry route of rucaparib, was converted into 4,6-disubstituted 2-aminocinnamic acid derivatives (ester or amide). The cyanide-catalyzed imino-Stetter reaction of aldimines derived from the resulting 2-aminocinnamic acid derivatives and a commercially available aldehyde afforded the desired indole-3-acetic acid derivatives. The final azepinone formation completed the total synthesis of rucaparib in 27% overall yield. To resolve the issues raised in the first-generation synthesis, we further developed a second-generation synthesis of rucaparib. The Heck reaction of a commercially available ortho-iodoaniline derivative with acrylonitrile provided 4,6-disubstituted 2-aminocinnamonitrile, which was subjected to the imino-Stetter reaction with the same aldehyde to provide the desired indole-3-acetonitrile product. Subsequent construction of the azepinone scaffold completed the total synthesis of rucaparib in 59% overall yield over three separation operations. The synthetic strategy reported herein can provide a highly practical route to access rucaparib from commercially available starting materials (5.2% overall yield in the current process chemistry route vs. 59% overall yield in the second-generation synthesis).

Total Synthesis of Rucaparib.

A concise total synthesis of rucaparib, an FDA-approved drug for ovarian and prostate cancers, is reported. The Heck reaction of the commercially available aryl iodide with acrylonitrile provided the desired (E)-2-aminocinnamonitrile derivative. A subsequent imino-Stetter reaction of the aldimine derived from 2-aminocinnamonitrile and aldehyde furnished indole-3-acetonitrile bearing the desired substituents at appropriate positions. The construction of the final azepinone scaffold via reduction of the nitrile group followed by seven-membered lactamization afforded rucaparib. Notably, the synthesis of rucaparib is achieved using commercially available starting materials in only three separation operations with 54% overall yield.