Palladium-Catalyzed Decarboxylative γ-Olefination of 2,5-Cyclohexadiene-1-carboxylic Acid Derivatives with Vinyl Halides

Recent advances in synthesis of stilbene derivatives via cross-coupling reaction

The stilbenes are undoubtedly some of the most significant moieties in various bioactive natural and synthetic structures, and they are considered privileged structures. In recent years, the preparation of these structures via cross-coupling reactions has attracted much attention. In the current review, we present a summary of the recent developments in the construction of stilbene and stilbene derivatives by carbon-carbon coupling reactions of organic compounds in the presence of transition metal catalysts or under metal-free conditions. In this context, we outline the features of the important reactions, some product yields, and challenging reaction mechanisms.

Catalytic Enantioselective Birch-Heck Sequence for the Synthesis of Phenanthridinone Derivatives with an All-Carbon Quaternary Stereocenter

Novel phenanthridinone analogues with an all-carbon quaternary stereocenter have been enantioselectively synthesized using the Birch-Heck sequence. Flat phenanthridinone structures have extensive bioactivity but consequently also suffer from poor therapeutic selectivity. The addition of a quaternary center to the phenanthridinone skeleton has the potential to generate more complex analogues with improved selectivity. Unfortunately, no general synthetic pathway to such derivatives exists. Herein we report a four-step process that transforms inexpensive benzoic acid into 22 different quaternary carbon-containing phenanthridinone analogues with a variety of substituents on all three rings: alkyl groups at the quaternary center; methyl, methoxymethyl, or para-methoxybenzyl on the amide nitrogen; and halogen and methyl substituents on the aryl ring. Good to very good enantioselectivity was demonstrated in the key intramolecular desymmetrizing Mizoroki-Heck reaction. Transformations of the Heck reaction products into molecules with potentially greater therapeutic relevance were also accomplished.

Visible-Light-Driven, Palladium-Catalyzed Heck Reaction of Internal Vinyl Bromides with Styrenes

Functionalized 1,3-dienes were efficiently accessed from visible-light-driven, palladium-catalyzed Heck reaction of S,S-functionalized internal vinyl bromides with styrenes under mild conditions. This Heck reaction showcased tolerance of a wide array of functional groups, afforded the target products in moderate to excellent yields through a radical reaction pathway. The resultant diene products could be further transformed to highly functionalized trisubstituted furan derivatives.

Functionalized Allyl Aryl Ether Synthesis from Benzoic Acids Using a Dearomatization and Decarboxylative Allylation Approach

A strategy toward the preparation of substituted allyl aryl ethers from benzoic acids via a dearomatization and decarboxylative allylation (DcA) reaction is presented. The benzoic acids undergo a dearomatization to give alkylated 2,5-cyclohexadienyl ketoesters which are subjected to a palladium-catalyzed DcA reaction, providing a variety of functionalized allyl aryl ethers. In addition, the combination of a resonance stabilized DcA reaction with a Claisen rearrangement for the synthesis of multisubstituted phenols and applying to dihydroplicatin B derivative synthesis is also presented.