Stereocontrolled Synthesis of a C<i><sup>n</sup></i>-C<i><sup>n</sup></i><sup>+7</sup>Building Block (“Eastern Moiety”) for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics Based on a Ring-Closing Metathesis and an Aldol Addition of a Lactone Enolate
作者:Sonja B. Kamptmann、Reinhard Brückner
DOI:10.1002/ejoc.201300183
日期:2013.10
A stereocontrolledsynthesis of epoxide 6, which represents the Cn–Cn+7 or “eastern moiety” building block for the title compounds, has been realized in 19 steps. Our synthesis started from tetrabromoacetone 26 and afforded dibromotriene 33b in six steps. The latter was subjected to a ring-closing metathesis, which gave the dibromovinyl-substituted lactone 34 in high yield. A highly stereoselective
Regioselective Rapid Analogue Syntheses of 1-Methyl-3,5-diarylpyrazoles via Palladium-catalysed Coupling to 3(5)-Pyrazolyl Nonaflates
作者:Ian Collins、Sylvie Bourrain、Mark Ridgill
DOI:10.1055/s-2004-820020
日期:——
Regioselective rapid analogue syntheses of 1-methyl-3,5-diarylpyrazoles were developed, based on Pd-catalysed couplings to 1-methyl-3(5)-arylpyrazole nonaflates, which offered an advantage in hydrolytic stability over the corresponding triflates. The new bifunctional reagent 1-methyl-3-bromo-pyrazol-5-yl nonaflate underwent highly chemoselective Pd-catalysed couplings to the nonaflate, followed by Suzuki couplings to the bromide, allowing sequential, regioselective introduction of the two aryl substituents.