Understanding the structural properties of p-xylylenebis(triphenylphosphonium) cation under different pH and anion conditions

Cis- and trans-conformers of the p-xylylenebis(triphenylphosphonium) dication can be accommodated in crystalline solids, depending on the pH of the solution and the presence of auxiliary anions (including p-sulfonatocalix[4]arene) and cations.

Improving phase-transfer catalysis by enhancing non-covalent interactions

A theoretical study of the interactions established between an alkaloid quinine-derived PTC and different anions of interest was performed. Ion pairing competes with an intermolecular hydrogen bond between the PT counteranion and potential HB donors.

Highly Enantioselective Synthesis of Fused Tri- and Tetrasubstituted Aziridines: aza-Darzens Reaction of Cyclic Imines with α-Halogenated Ketones Catalyzed by Bifunctional Phosphonium Salt

The first enantioselective aza-Darzens reaction of cyclic imines with α-halogenated ketones was realized under mild reaction conditions by using amino-acid-derived bifunctional phosphonium salts as phase-transfer promoters. A variety of structurally dense tri- and tetrasubstituted aziridine derivatives, containing benzofused heterocycles as well as spiro-structures, were readily synthesized in high yields with excellent diastereo- and enantioselectivities (up to >20:1 d.r. and >99.9 % ee). The highly functionalized aziridine products could be easily transformed into different classes of biologically active compounds.

Chiral Phase-Transfer Catalysts with Hydrogen Bond: A Powerful Tool in the Asymmetric Synthesis

Asymmetric phase-transfer catalysis has been widely applied into organic synthesis for efficiently creating chiral functional molecules. In the past decades, chiral phase-transfer catalysts with proton donating groups are emerging as an extremely significant strategy in the design of novel catalysts, and a large number of enantioselective reactions have been developed. In particular, the proton donating groups including phenol, amide, and (thio)-urea exhibited unique properties for cooperating with the phase-transfer catalysts, and great advances on this field have been made in the past few years. This review summarizes the seminal works on the design, synthesis, and applications of chiral phase-transfer catalysts with strong hydrogen bonding interactions.

Asymmetric synthesis of spiro-structural 2,3-dihydrobenzofuransviathe bifunctional phosphonium salt-promoted [4 + 1] cyclization ofortho-quinone methides with α-bromoketones

A practical and scalable method for highly stereoselective construction of spiro-2,3-dihydrobenzofuransviacyclization ofortho-quinone methides and α-bromoketones by bifunctional phosphonium salt catalysis was developed.

Phosphine Organocatalysis

The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon-carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita-Baylis-Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material-nucleophiles, dinucleophiles, electrophiles, and electrophile-nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon-carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon-carbon multiple bond-containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide-generating reactions.

Long sought synthesis of quaternary phosphonium salts from phosphine oxides: inverse reactivity approach

Reaction of Grignard reagents with chlorophosphonium salts provides a conceptually new synthesis of quaternary phosphonium salts from phosphine oxides by using inverse reactivity at phosphorus.