An application of the classical Ritter reaction for the synthesis of unsymmetrical di and trisubstituted ureas catalyzed by FeCl(3) is described. The protocol is of significant interest in view of the easy availability of precursors, mild reaction conditions employed and interestingly its applicability for the alkylation of alcohols capable of forming stable carbocationic intermediates even to ...

The title compound, C(23)H(35)BrO(3), synthesized by esterification and bromination of isosteviol, comprises a fused four-ring system. Two of the six-membered rings adopt a regular chair conformation, whereas the remaining six-membered ring is an unsymmetrical distorted chair. The stereochemistry at the two six-membered ring junctions is trans, while the five-membered ring adopts an envelope co...

In the title compound, C(17)H(16)N(5)O, the central tetra-zine ring adopts an unsymmetrical boat conformation with the two C atoms as flagpoles. This compound can be considered as having homoaromaticity. The crystal structure is stabilized by inter-molecular C-H⋯O inter-actions between a benzene H atom and the carbonyl O atom.

The first regioselective oxidative coupling of 2-hydroxycarbazoles is described. With a vanadium catalyst and oxygen as the terminal oxidant, dimers with an ortho-ortho' coupling pattern were obtained with high selectivity. Further oxidation led to ortho'-ortho' coupling to generate a tetramer, which provided insight that the atropisomerization barriers of the unsymmetrical biaryl bonds are muc...

A facile synthesis of unsymmetrical N,N'-diarylureas is described. The utilization of the Pd-catalyzed arylation of ureas enables the synthesis of an array of diarylureas in good to excellent yields from benzylurea via a one-pot arylation-deprotection protocol, followed by a second arylation.

The syntheses of unsymmetrical N-heterocyclic carbenes (NHCs) that contain a single N-bound icosahedral carborane anion substituent are reported. Both anionic C-2 and doubly deprotonated dianionic C-2/C-5 NHC lithium complexes are isolated. The latter species is formed selectively, which reveals a surprising directing effect conveyed by icosahedral carborane anion substituents.

In the unsymmetrical title complex, [Ni(C(20)H(23)N(4)O(4))]ClO(4), the coordination geometry for the Ni(II) atom can be described as square planar. The aromatic rings in the two ligands are almost vertical, with a dihedral angle of 85.3°. In the crystal, cations and anions are linked by weak C(N)-H⋯O hydrogen bonding.

We have successfully prepared an unsymmetrical analogue of a Katsuki-type salen ligand having a single hydroxyalkyl group at its 6-position, and also its Mn(III) complex; attachment of the complex to a polymer gives a highly enantioselective and recoverable catalyst for epoxidation of 1,2-dihydronaphthalene.

SPIHT (Set Partitioning In hierachical trees), being an efficient coding method for wavelet coefficients, has acquired more and more widely application, especially in image/video compression fields. But, conventional SPHIT have some obvious limitions. For example, when for the color image compression, polarmetric SAR image compression, or multispectrum image compression and other multi-channel ...