RESUMO
An unprecedented highly regio- and enantioselective rhodium-catalyzed addition of 1,3-diketones to terminal and 1,1-disubstituted allenes furnishing asymmetric tertiary and quaternary all-carbon centers is reported. By applying a RhI /phosphoramidite/TFA catalytic system under mild conditions, the desired chiral branched α-allylated 1,3-diketones could be obtained in good to excellent yields, with perfect regioselectivity and in high enantioselectivity. The reaction shows a broad functional-group tolerance on both reaction partners highlighting its synthetic potential.
RESUMO
A new method for the rhodium-catalyzed regioselective C-C bond formation using terminal alkynes and 1,3-dicarbonyl compounds to achieve valuable branched α-allylated 1,3-dicarbonyl products is reported. With a Rh(I)/DPEphos/p-CF3-benzoic acid as the catalyst system, the desired products can be obtained in good to excellent yields and with perfect regioselectivity. A broad range of functional groups were tolerated, and first experimental insights of a plausible reaction mechanism were obtained.
RESUMO
A number of isosteres (oxadiazoles, thiadiazoles, tetrazoles and diazines) of benzocaine were prepared and evaluated for their capacity to induce methemoglobinemia-with a view to their possible application as humane pest control agents. It was found that an optimal lipophilicity for the formation of methemoglobin (metHb) in vitro existed within each series, with 1,2,4-oxadiazole 3 (metHb%=61.0±3.6) and 1,3,4-oxadiazole 10 (metHb%=52.4±0.9) demonstrating the greatest activity. Of the 5 candidates (compounds 3, 10, 11, 13 and 23) evaluated in vivo, failure to induce a lethal end-point at doses of 120mg/kg was observed in all cases. Inadequate metabolic stability, particularly towards hepatic enzymes such as the CYPs, was postulated as one reason for their failure.
