Base-Mediated Cyclopentannulation of Ynones with Amino Crotonates for Regio- and Stereoselective Synthesis of Pentafulvenes and Cyclopenta[c]quinolines

Formation of cyclopenta[c]quinolines through visible-light-induced photoredox cascade bis-annulations of 1,7-enynes with sulfoxonium ylides

A novel visible-light-driven photoredox-catalyzed cascade bicyclization of 1,7-enynes with aqueous sulfoxonium ylides is reported. The reaction is highly chemoselective with three new C-C bonds, two new rings, and an all-carbon quaternary stereocenter constructed in a one-pot fashion. This mild protocol features a remarkably broad substrate scope with good functional group tolerance, providing a general and practical approach to access various cyclopenta[c]quinolines.

An Approach to Functionally Embellished o-Alkynylbenzoates or Furan-3(2H)-ones from Diynones and DMAD: Controlled Divergence and Product Selectivity

The discovery of reaction regime controlled product diversification in a one-pot reaction between diynones and dimethyl-1,3-acetonedicarboxylate (DMAD) to selectively furnish either functionally unique pentasubstituted o-alkynylbenzoates or fully substituted furan-3(2H)-ones is delineated. The potential of these two versatile platforms to enter new utilitarian chemical space has also been explored.

Palladium-catalyzed cyclizative cross coupling of ynone oximes with 2-haloaryl N-acrylamides for isoxazolyl indoline bis-heterocycles

Metal-catalyzed cyclizative cross-coupling reactions have attracted enormous attention due to their unique cascade nature. We demonstrated, herein, a dual-cyclizative coupling of ynone oxime ethers with acrylamides for the synthesis of methylene-linked isoxazolyl 2-oxindoles. The cascade was triggered by a palladium(II)-catalyzed ynone oxime ether cyclization, which underwent a Heck-type coupling intercepted by an aryl iodide insertion. Control experiments were carried out to understand the mechanism.

Rhodium-Catalyzed Regioselective Double Annulation of Enaminones with Propargyl Alcohols: Rapid Access to Arylnapthalene Lignan Derivatives

We present here a rhodium-catalyzed oxidative three-point double annulation of enaminones with propargylic alcohols via a C-H and a C-N bond activation to access arylnaphthalene-based lignan derivatives. The key step in the reaction is the regioselective insertion of propargylic alcohol into the rhoda-cycle, a result of hydroxyl rhodium coordination. Necessary control experiments and KIE studies were conducted to determine the mechanism.

Diastereoselective [2+2+1] Hydrative Annulation of Phenol-Linked 1,6-Enynes with Acetylenes Through Rhodium Catalysis: A Rapid Access to Cyclopenta[b]benzofuranols

An unprecedented [2+2+1] hydrative annulation of 1,6-enynes with terminal alkynes is achieved using catalytic cationic Rh(I). Thus, a modular assembly of cyclopenta[b]benzofuranols with two consecutive quarternary stereocenters is achieved from readily available alkynes. The reaction is proposed to go through a sequence of 5-membered rhoda-cycle formation, regioselective acetylene insertion, 1,5 H-shift, substrate controlled stereoselective addition of water molecule followed by 1,2-rhodium migration gave contracted rhoda-cycle D and reductive elimination. Necessary control/labelling experiments were conducted to gain insight in to the mechanism.

Regioselective benzannulation of allylic sulfur ylides with ynones: a rapid access to substituted thioanisoles

The efficiency and selectivity of annulation reactions are often difficult to control in the presence of multiple potential reactive centers, like in the case of allylic sulfur ylides (ASY). Here, we describe a novel base mediated [3+3] benzannulation of ASY and readily available alkynones, which accomplishes the regioselective formation of multisubstituted thioanisoles, highly sought after chemical scaffolds. A new reactivity pattern of ASY has been unearthed, where it acted as both a 3C component and sulfur source in benzannulation. Use of a widely available base, operational simplicity and broad substrate scope are the additional salient features of the conversion.