A route to unsymmetrical polyene dialdehydes is described. The utility of these intermediates is illustrated by a synthesis of okenone. The stereochemistry assigned to methyl natural bixin has been confirmed by preparation of the cis-4 isomer. Support has been obtained for the cis-6 formulation of natural cis-crocetin. Oxidation of astacene with manganese dioxide yields violaxanthin. The synthe...

An efficient "one-pot" approach to multiple substituted ureas from N-arylcyanamide and diaryliodonium salts has been presented. The two-step procedure involved the weak base-promoted chemoselective arylation of secondary amines with diaryliodonium and Cu-catalyzed nucleophilic addition of N-arylcyanamide with second diaryliodonium. The diverse unsymmetrical arylureas were obtained in up to 91% ...

An efficient La2O3-catalyzed new route for the carbon-carbon bond formation in particular, symmetrical and unsymmetrical biphenyls has been developed, which proceeds through carbon-carbon coupling reaction of aryl iodides with boronic acids. The reaction provided the desired products in moderate-to-good yields with a wide range of functional group tolerance.

Acyclic allylic monofluorides were prepared by electrophilic fluorination of branched (E)-allylsilanes with Selectfluor. These reactions proceeded with efficient transfer of chirality from the silylated to the fluorinated stereocentre. Upon double fluorination, an unsymmetrical ethyl syn-2,5-difluoroalk-3-enoic ester was prepared, the silyl group acting as an anti stereodirecting group for the ...

The synthesis of unsymmetrical diaryl ketones via the Fukuyama coupling of thioesters and organozinc reagents is described. Typically, the synthesis of diaryl ketones using this methodology provides low yields. The simple complex, Pd(dba)(2), was found to convert a variety of aryl thioesters to diaryl ketones in good yields.

The synthesis of a family of O-silylcarbamates from the corresponding silylamines has been achieved simply by heating the silylamine in supercritical carbon dioxide (scCO2), and these O-silylcarbamates have been shown to be effective precursors for the synthesis of a range of symmetrical and unsymmetrical ureas.

The synthesis of unsymmetrical 2,5-disubstituted thiophenes by selective and sequential palladium-catalyzed cross-coupling reactions of indium organometallics with 2,5-dibromothiophene is reported. Following an iterative coupling sequence, α-oligothiophenes were synthesized in good yields and with high atom economy.

A diblock copolymer is designed to have incompatible blocks, unsymmetrical block lengths, and a reversible linkage. This copolymer self-assembles into nanostructured cylindrical morphology in thin films. Removal of the nanosized cylinders by breaking the reversible linkage then affords nanoporous membranes featuring a chemically reactive functionality in the pores.

A novel Lewis acid InBr3-catalyzed direct cross-coupling reaction of arylboronic acids with diorgano diselenides and ditellurides without any additive has been developed. The reactions generated the corresponding unsymmetrical diorgano monoselenides and monotellurides in good to excellent yields. The method has advantages of broad substrate scope, simple operation, mild reaction conditions and ...

Using Ag2CO3 as an additive, we developed the Pd-catalyzed intermolecular C-H/C-H cross-coupling of pyridine N-oxides with five-membered heterocycles such as 1-benzyl-1,2,3-triazoles, thiophens and furans. This protocol provides an efficient and regioselective approach for the synthesis of unsymmetrical biheteroaryl molecules.