Polymer-supported triphenylphosphine: application in organic synthesis and organometallic reactions

Copper-Catalyzed Stereoselective Borylation and Palladium-Catalyzed Stereospecific Cross-Coupling to Give Aryl C-Glycosides

Metabolically stable C-glycosides are an essential family of compounds in bioactive natural products, therapeutic agents, and biological probes. For their application, development of synthetic methods by connecting glycosides and aglycons with strict stereocontrol at the anomeric carbon, as well as with high functional-group compatibility and environmental compatibility is a pivotal issue. Although Suzuki-Miyaura-type C(sp³ )-C(sp² ) cross-coupling using glycosyl boronates is a potential candidate for the construction of C-glycosides, neither the cross-coupling itself nor the facile synthesis of the coupling precursor, glycosyl boronates, have been achieved to date. Herein, it was succeeded to develop a copper-catalyzed stereoselective one-step borylation of glycosyl bromides to glycosyl boronates and palladium-catalyzed stereospecific cross-coupling of β-glycosyl borates with aryl bromides to give aryl β-C-glycosides, in which the β-configuration of the anomeric carbon of the glycosyl trifluoroborates is stereoretentively transferred to that of the resulting aryl C-glycosides.

One-Step Synthesis of Acylborons from Acyl Chlorides through Copper-Catalyzed Borylation with Polystyrene-Supported PPh3 Ligand

We developed a one-step synthesis of acylborons from both readily available acyl chlorides and bis(pinacolato)diboron through copper(I)-catalyzed borylation. Under the reaction conditions using ^tBuOLi, polystyrene-supported triphenylphosphine as a copper ligand was found to promote the borylation of acyl chlorides while suppressing alcoholysis. This method enables the facile synthesis of potassium acyltrifluoroborates.

Alkylation of quinoxalin-2(1H)-ones using phosphonium ylides as alkylating reagents

A practical and efficient methodology for the construction of 3-alkylquinoxalinones through base promoted direct alkylation of quinoxalin-2(1H)-ones with phosphonium ylides as alkylating reagents under metal- and oxidant-free conditions was developed. Various 3-alkylquinoxalin-2(1H)-ones were easily obtained in good to excellent yields. Tentative mechanistic studies suggest that this reaction is likely to involve a nucleophilic addition-elimination process.

Nucleophilic Phosphine Catalysis: The Untold Story

This Minireview provides insight into the early history of nucleophilic phosphinocatalysis. The concepts of 1,4-addition of a tertiary phosphine to an α,β-enone and of equilibrium between the resulting phosphonium zwitterion and phosphonium ylide established a fundamental basis for the development of several classical transformations, including the Rauhut-Currier, Morita, McClure-Baizer-Anderson, and Oda reactions.

Synthesis of Piperidine Nucleosides as Conformationally Restricted Immucillin Mimics

The de novo synthesis of piperidine nucleosides from our homologating agent 5,6-dihydro-1,4-dithiin is herein reported. The structure and conformation of nucleosides were conceived to faithfully resemble the well-known nucleoside drugs Immucillins H and A in their bioactive conformation. NMR analysis of the synthesized compounds confirmed that they adopt an iminosugar conformation bearing the nucleobases and the hydroxyl groups in the appropriate orientation.

Phosphorus-Recycling Wittig Reaction: Design and Facile Synthesis of a Fluorous Phosphine and Its Reusable Process in the Wittig Reaction

This study shows that phosphorus sources can be recycled using the appropriate fluorous phosphine in the Wittig reaction. The designed fluorous phosphine, which has an ethylene spacer between its phosphorus atom and the perfluoroalkyl group, was synthesized from air-stable phosphine reagents. The synthesized phosphine can be used for the Wittig reaction process to obtain various alkenes in adequate yields and stereoselectivity. The concomitantly formed fluorous phosphine oxide was extracted from the reaction mixture using a fluorous biphasic system. The fluorous phosphine was regenerated by reducing the fluorous phosphine oxide with diisobutylaluminum hydride. Finally, a series of gram scale phosphorus recycling processes were performed, which included the Wittig reaction, separation, reduction, and reuse.