A New Alkoxyallene-Based [3+2] Approach to the Synthesis of Highly Substituted Cyclopentenones
作者:Hans-Ulrich Reissig、Branislav Dugovič
DOI:10.1055/s-2008-1042895
日期:——
Lithiated methoxyallene 1 and aldehydes 2 provided after base- or gold-catalyzed cyclization dihydrofurans 3 which were oxidatively cleaved giving α,β-unsaturated γ-ketoaldehydes 4 as key intermediates. These smoothly underwent intramolecular aldol addition to furnish highly substituted cyclopentene derivatives 5 in good yields. Due to their dense pattern of functional groups compounds 5 are versatile
Oxidative Cleavage of 3-Alkoxy-2,5-dihydrofurans and its Application to the De Novo Synthesis of Rare Monosaccharides as Exemplified byL-Cymarose
作者:Malte Brasholz、Hans-Ulrich Reissig
DOI:10.1002/anie.200604078
日期:2007.2.26
3-Alkoxy-2,5-dihydrofurans by Gold-Catalyzed Allenyl Cyclizations and Their Transformation into 1,4-Dicarbonyl Compounds, Cyclopentenones, and Butenolides
The addition of lithiated alkoxyallenes to carbonyl compounds furnishes allenyl alcohols, which undergo a highly efficient and chemoselective 5-endo-trig cyclization to 3-alkoxy-2,5-dihydrofurans catalyzed by gold(I) chloride. The dihydrofurans produced can be either oxidized to β-alkoxy butenolides by a manganese(III) acetatecatalyzedradicaloxidation with tert-butyl hydroperoxide, or transformed