The rhodium-catalyzed methylenation of aldehydes using trimethylsilyldiazomethane and triphenylphosphine produces a variety of terminal alkenes in excellent yields. These mild and nonbasic reaction conditions allow the conversion of enolizable substrates (keto aldehydes and nonracemic alpha-substituted aldehydes) to terminal alkenes without epimerization. Optimization of the reaction conditions led
Anomeric oxygen to carbon rearrangements of alkynyl tributylstannane derivatives of furanyl (γ)- and pyranyl (δ)-lactols
作者:Marianne F. Buffet、Darren J. Dixon、Steven V. Ley、Dominic J. Reynolds、R. Ian Storer
DOI:10.1039/b316858a
日期:——
Tetrahydropyran and tetrahydrofuran containing natural products, drugs and agrochemicals often possess carbonâcarbon bonds adjacent to the heteroatom. Consequently, new methods for the construction of anomeric carbonâcarbon bonds are of considerable importance. We have devised a new strategy to access these systems that requires the treatment of O-glycoside alkynyl tributylstannane derivatives of furanyl and pyranyl lactols with Lewis acid to effect oxygen to carbon rearrangements. This leads to the formation of the corresponding carbon linked alkynol products that can be further manipulated to produce key structural motifs and building blocks for the assembly of complex molecules.
Diastereoselective oxygen to carbon rearrangements of anomerically linked enol ethers and the total synthesis of (+)-(S,S )-(cis-6-methyltetrahydropyran-2-yl)acetic acid, a component of civet
作者:Darren J. Dixon、Steven V. Ley、Edward W. Tate
DOI:10.1039/b001243m
日期:——
range of enol ethers, linked via their oxygen atom to the anomeric centre of a pyran ring system, was shown to undergo oxygen to carbon rearrangement upon treatment with a Lewisacid to give the corresponding 2-carbon substituted products. At low temperature, trimethylsilyl trifluoromethanesulfonate catalysed rearrangements of anomerically linked 6-substituted tetrahydropyranyl enol ethers gave selectively
Efficient Synthesis of γ-Lactones via Gold-Catalyzed Tandem Cycloisomerization/Oxidation
作者:Chao Shu、Meng-Qi Liu、Yu-Zhe Sun、Long-Wu Ye
DOI:10.1021/ol302323a
日期:2012.9.21
A novel Au-catalyzed tandem cycloisomerization/oxidation of homopropargyl alcohols was developed. Various γ-lactones can be accessed readily by utilizing this strategy. Notably, the mechanism of this reaction is distinctively different from the related Ru-catalyzed reactions where the ruthenium vinylidene intermediate was proposed.