Transition-metal-free approaches to 2,3-diarylated indenones from 2-alkynylbenzaldehydes and phenols with tunable selectivity

Phosphine-Based Porous Organic Polymer-Stabilized Palladium Nanoparticle Catalyst for the Regioselective Synthesis of Indenones

Phosphorus-embedded porous organic polymers (P-POPs) play a vital role in catalysis and sustainable chemical synthesis. This study uses an olefin-linked P-POP to stabilize Pd nanoparticles that catalyze Larock's annulation to synthesize symmetrical indenones in high yields. Unsymmetric indenones were obtained with exclusive regioselectivities by employing an intramolecular dicarbofunctionalization of a modular alkyne. The approach addresses selectivity challenges in indenone synthesis and broadens the reaction scope by incorporation of aryl halides. The catalyst is robust and recyclable.

A HMPA-H2O mediated oxygenative carbocyclization of 2-alkynylphenyl-substituted p-quinone methides to indenones

Herein, we report a transition-metal and base-free protocol to access a wide range of functionalized indenone derivatives through a HMPA-H2O-mediated oxygenative annulation of 2-alkynylphenyl-substituted p-quinone methides. This method worked effectively for most of the p-QMs investigated and the corresponding indenone derivatives were obtained in moderate to good yields. This methodology was further extended to the formal synthesis of one of the resveratrol based natural products, (±)-isopaucifloral F.

Csp2-H functionalization of phenols: an effective access route to valuable materials via Csp2-C bond formation

In the vast majority of top-selling pharmaceutical and industrial products, phenolic structural motifs are highly prevalent. Non-functionalized simple phenols serve as building blocks in the synthesis of value-added chemicals. It is worth mentioning that lignin, being the largest renewable biomass source of aromatic building blocks in nature, mainly consists of phenolic units, which enable the production of structurally diverse phenols. Given their remarkable applicability in the chemical value chain, many efforts have been devoted to increasing the molecular complexity of the phenolic scaffold. Among the key techniques, direct functionalization of Csp2-H is a powerful tool, enabling the construction of new Csp2-C bonds in an economical and atomic manner. Herein we present and summarize the large plethora of direct Csp2-H functionalization methods that enables scaffold diversification of simple, unprotected phenols, leading to the formation of new Csp2-C bonds. In this review article, we intend to summarize the contributions that appeared in the literature mainly in the last 5 years dealing with the functionalization of unprotected phenols, both catalytic and non-catalytic. Our goal is to highlight the key findings and the ongoing challenges in the stimulating and growing research dedicated to the development of new protocols for the valorization of phenols.

Palladium Catalyzed Dicarbonylation of α-Iodo-Substituted Alkylidenecyclopropanes: Synthesis of Carbamoyl Substituted Indenones

A palladium catalyzed dicarbonylation of α-iodo-substituted ACPs for the synthesis of carbamoyl substituted indenones has been developed. Two carbonyl groups were incorporated into the product with the cleavage of the proximal C-C bond of the ACPs. A broad range of carbamoyl substituted indenones were efficiently prepared in good to excellent yields.