TEMPO-Catalyzed Aminophosphinoylation of Ethers via Tandem C(sp3)-H and C(sp3)-O Bond Cleavage.

A new TEMPO-catalyzed aminophosphinoylation of ethers with amines and H-phosphine oxides was developed for the synthesis of α-aminophosphine oxides. This metal-free aminophosphinoylation reaction could be conducted under mild conditions through tandem C(sp3)-H and C(sp3)-O bond cleavage. The present method offers a facile and efficient approach to broad range of α-aminophosphine oxide derivatives in moderate to good yields with excellent functional group tolerance.

Direct use of dioxygen as an oxygen source: catalytic oxidative synthesis of amides.

The first transition-metal-catalyzed direct oxidative synthesis of amides by using dioxygen as an oxygen source has been developed under mild conditions, in which DBU was used as the key additive. The present methodology, which utilizes dioxygen as an oxidant and oxygen source and cheap copper salts as catalysts, opens up an interesting and attractive avenue for the synthesis of amide functionality.

Gold-catalyzed three-component tandem process: an efficient and facile assembly of complex butenolides from alkynes, amines, and glyoxylic acid.

An efficient and facile gold-catalyzed three-component tandem process for the assembly of two types of highly functionalized butenolides has been developed. In this reaction system, more than four chemical bonds are formed by a single gold catalyst. The present tandem protocol includes a direct coupling of alkynes, amines, and glyoxylic acid and subsequent exclusively endo-selective cycloisomerization of alkynoic acids along with intermolecular electrophilic trapping; it utilizes three simple and commercially available starting materials to assemble architecturally complex and appealing butenolide scaffolds bearing other reactive sites for further manipulation.

Phospholipid-protein adducts of lipid peroxidation: synthesis and study of new biotinylated phosphatidylcholines.

Oxidative stress gives rise to a number of electrophilic aldehydes from membrane phospholipids, and these compounds have been linked to pathophysiologic events associated with the progression of cardiovascular disease. A headgroup biotinylated phosphatidylcholine (PC) has been prepared, and its oxidation chemistry has been studied. Biotin or biotin-sulfoxide groups were attached to PC at the ammonium headgroup via a di-ethylene glycol link. The modified phospholipids have calorimetric and colloidal properties similar to those of the parent. The oxidation of PLPBSO (the biotin-sulfoxide analogue of 1-palmitoyl-2-linoleoylglycerylphosphatidylcholine, PLPC) was studied under a variety of conditions. PLPBSO, like PLPC, undergoes oxidation to give electrophiles that adduct to small model peptides as well as to isolated proteins such as human serum albumin. PLPBSO incorporates into human blood plasma, and treatment of the plasma with water soluble free radical initiators gives rise to a number of biotinylated plasma proteins that can be isolated via (strept)avidin affinity. Isolated peptide or protein-lipid adducts can be identified by proteomics analyses, and studies on model peptides show that phospholipid-protein adduction sites can be identified by known algorithms. Biotinylated lipids such as PLPBSO and modern proteomics tools would appear to provide a new approach to exploring the chemistry and biology of membrane peroxidation associated with oxidative stress.

Catalytic asymmetric alkynylation of alpha-imino ester: a versatile approach to optically active unnatural alpha-amino acid derivatives.

The catalytic asymmetric introduction of alkynyl functionality to alpha-amino acid derivatives was realized by the direct addition of terminal alkynes to alpha-imino ester in the presence of chiral Cu(I) complex under mild reaction conditions. Owing to the rich chemistry to which alkyne can be subjected, the present system provides a remarkably versatile tool for the construction of optically active alpha-amino acid derivatives. Good yields and enantiomeric excess values were achieved with an array of terminal alkynes and challenging, biologically active, unnatural alpha-amino acid derivatives could be conveniently obtained.

A remarkably effective copper(II)-dipyridylphosphine catalyst system for the asymmetric hydrosilylation of ketones in air.

The combination of catalytic amounts of optically active dipyridylphosphine and CuF(2) along with hydride donor PhSiH(3) generated in situ a remarkably reactive catalyst system (substrate-to-ligand molar ratio up to 100,000) for the highly enantioselective hydrosilylation of a broad spectrum of aryl alkyl ketones (up to 97% enantiomeric excess) in normal atmosphere and at mild conditions (ambient temperature to -20 degrees C, compatible with traces of moisture) in the absence of base additives. Furthermore, a highly effective catalytic asymmetric hydrosilylation of unsymmetrical diarylketones using this catalyst system was also realized (up to 98% enantiomeric excess). The introduction of the dipyridylphosphine ligands in the air-accelerated and inexpensive metal-mediated asymmetric hydrosilylation of ketones makes the present system highly attractive and thus provides an excellent opportunity for practical applications.

Highly enantioselective phenyl transfer to aryl aldehydes catalyzed by easily accessible chiral tertiary aminonaphthol.

A new chiral tertiary aminonaphthol ligand 3b served as a highly efficient ligand for the asymmetric catalytic phenyl transfer to aromatic aldehydes and a variety of chiral diarylmethanols was prepared in high ee values (ee up to 99%) and chemical yields. The straightforward syntheses of both 3b and its enantiomer provide an excellent opportunity for large-scale applications.

Remarkably diastereoselective synthesis of a chiral biphenyl diphosphine ligand and its application in asymmetric hydrogenation.

Essentially complete atropdiastereoselectivity was realized in the preparation of biaryl diphosphine dioxide by asymmetric intramolecular Ullmann coupling and oxidative coupling with central-to-axial chirality transfer. A bridged C(2)-symmetric biphenyl phosphine ligand possessing additional chiral centers on the linking unit of the biphenyl groups was synthesized. No resolution step was required for the preparation of the enantiomerically pure chiral ligand. These findings offer a general and practical tool for the development of previously uninvestigated atropdiastereomeric biaryl phosphine ligands. The diphosphine ligand was found to be highly effective in the asymmetric hydrogenation of alpha- and beta-ketoesters, 2-(6'-methoxy-2'-naphthyl)propenoic acid, beta-(acylamino)acrylates, and enol acetates.

A convenient, one-step synthesis of optically active tertiary aminonaphthol and its applications in the highly enantioselective alkenylations of aldehydes.

Optically active tertiary aminonaphthol 1 was obtained by a new, convenient procedure and was found to catalyze the enantioselective alkenylation of various aldehydes with high ee values, which provides a practical method for the synthesis of chiral (E)- allyl alcohols.

(R)-(6,6'-Dihydroxybiphenyl-2,2'-diyl)bis(diphenylphosphine oxide) methanol solvate.

The title compound, C(36)H(28)O(4)P(2).CH(4)O, was synthesized directly from the methoxy analogue. The crystal structure shows that one OH group interacts with an O atom of a phosphine oxide group in an adjacent molecule, while the other OH group complexes with the methanol solvent molecule via intermolecular hydrogen bonds. An O atom of one phosphine oxide group interacts with the hydroxy H atom of methanol via a hydrogen bond. There are intra- and intermolecular pi-pi interactions between the phenyl rings. All these interactions result in the formation of supramolecular chiral parallelogram channels via self-assembly.