A new concept for catalytic reactions in aqueous media is demonstrated by using a temperature‐responsive polymer support, poly(N‐alkylacrylamide), which is converted into a catalyst by assembly with phosphotungstic acid. At high temperature, the catalyst is highly active in the oxidation of alcohols with H2O2 owing to the formation of emulsions, whereas the product and catalyst are easily separated at low temperature (see scheme).
The atropisomeric enantiomers of 7-, 8-, and 9-membered-ring dibenzolactams were separated by using chiral HPLC, and their stereochemistries were clarified by using X-ray crystallographic analysis. The atropisomers showed high stereochemical stability with the 8-membered ring being the most stable. In 7- and 8-membered dibenzolactams, highly stereoselective C7-methylation proceeded from the lower side of the ring to provide the products with a C7-methyl group in the pseudoaxial orientation, which converted to thermodynamically more stable isomers with the pseudoequatorial C7-methyl group. In 9-membered dibenzolactam, C7-methylation occurred from the opposite (upper) side of the ring to provide a thermodynamically stable product with the pseudoequatorial C7-methyl group.
To elucidate the active conformation of indometacin that differentiates between cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), the stereochemistry around the N-benzoylated indole moiety of indometacin was studied. Resolution of stable atropisomers as representative conformations was found to be possible by restricting rotation about the N-C7' and/or C7'-C1' bond. Only the aR-isomer showed specific inhibition of COX-1, and COX-2 was not inhibited by either atropisomer.
Dibenzo[b,d]azepin-6-ones (2a,b) were separated by chiral HPLC into the aR- and aS-atropisomers with high stereochemical stability, and methylation at C7 of 2a stereoselectively gave the (aR*,7R*) isomer (4a), which converted to the thermodynamically stable (aS*,7R*) atropisomer (5a) after heating.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.