RESUMO
The benzothiazine nucleus is a relatively unexplored class of compounds, from the standpoint of both synthetic chemistry and biological activity. We have developed a rapid, high-yielding synthesis of benzothiazines in which a precursor aryl thiourea is prepared on solid phase. Addition of trifluoroacetic acid catalyzes a conjugate addition reaction to form the desired heterocycle and releases it from the resin.
RESUMO
[structure: see text] We have developed an apparatus for carrying out redox-coupled chromium-manganese or chromium-zinc reactions on solid-supported substrates which allows recycling of the stoichiometric reductant. In addition to providing a greatly simplified procedure for these reactions, we observe striking differences in the recyclability of Mn and Zn. A preliminary extension of the methodology to the catalytic coupling of allylchromium reagents with solid-supported aldehydes is also reported.
RESUMO
From oligonucleotides to orangutans, nature has found darwinian evolution to be the most efficient means of optimizing populations of organisms - or molecules. Recently, several research groups have begun adapting darwinian evolution to the identification of small molecules with specific properties. Although still at an early stage, this new field of 'dynamic diversity' shows promise as a method for the identification of high-affinity ligands for biomolecules.
RESUMO
A wide range of aromatic nitro compounds can be reduced to anilines through the use of a Cr(II)/Mn(0) redox couple in the presence of trimethylsilyl chloride [TMSCl, Eq. (1)]. Only 0.25 equivalents of chromium are required to reduce solid-supported nitroarenes (R=solid support); this represents a rare case of transfer catalysis between two solid phases. The reaction is also amenable to solution-phase synthesis (R=OH).
