Simple One-pot Conversion of Aldehydes and Ketones to Enals
作者:Petr Valenta、Natalie A. Drucker、Jeffrey W. Bode、Patrick J. Walsh
DOI:10.1021/ol9005757
日期:2009.5.21
A simple and efficient method to convert aldehydes into α,β-unsaturated aldehydes with a two-carbon homologation is presented. Hydroboration of ethoxy acetylene with BH3·SMe2 generates tris(ethoxyvinyl) borane. Transmetalation with diethylzinc, addition to aldehydes or ketones, and acidic workup affords enals. When the addition is quenched with anilinium hydrochloride, 1,2-dithioglycol, or acetic anhydride
An Atom-Economic and Selective Ruthenium-Catalyzed Redox Isomerization of Propargylic Alcohols. An Efficient Strategy for the Synthesis of Leukotrienes
作者:Barry M. Trost、Robert C. Livingston
DOI:10.1021/ja804105m
日期:2008.9.10
secondary propargylicalcohols in good yields to provide trans enals and enones exclusively. Readily available indenylbis(triphenylphosphine)ruthenium chloride, in the presence of indium triflate and camphorsulfonic acid, gives the best turnover numbers and reactivity with the broadest range of substrates. Deuterium labeling experiments suggest that the process occurs through propargylic hydride migration
case of 4c the reaction was also monitored by online mass spectrometry. A lower temperature for the retro-enereaction of 4c, eliminating an imine, than for 4a, eliminating formaldehyde, is in agreement with a lower calculated activation barrier (167 and 181 kJ mol(-1), respectively, at the G2(MP2,SVP) level of theory). The allenic amide 11 undergoes an analogous retro-enereaction to the (unobserved)
A novel protocol for the annulation of tropone to enals involving nucleophilic heterocyclic carbene (NHC) catalyzed homoenolate formation has been developed. Interestingly, the reaction led to bicyclic δ-lactones instead of the expected γ-spirolactones, presumably by the uncommon [8 + 3] annulation pathway. The strategy works well with a variety of enals.