(E)-Cycloalkenes and (E,E)-cycloalkadienes by ring closing diyne- or enyne–yne metathesis/semi-reduction
作者:Fabrice Lacombe、Karin Radkowski、Günter Seidel、Alois Fürstner
DOI:10.1016/j.tet.2004.05.042
日期:2004.8
A concise, practical and stereoselective entry into macrocyclic (E)-alkenes is outlined comprising a sequence of ring closing alkyne metathesis (RCAM), trans-selective hydrosilylation of the resulting cycloalkynes catalyzed by [Cp*Ru(MeCN)(3)]PF6, and a protodesilylation of the ensuing vinylsilanes with AgF in aq. THF/MeOH. Moreover, the first examples of intramolecular enyne-yne metathesis reactions catalyzed by the Schrock alkylidyne complex (tBUO)(3)W drop CCMe3 are reported; the resulting cyclic enynes can be converted along similar lines into the corresponding (E,E)-configured 1,3-dienes in good overall yields. Cycloalkyne 4 and the (E)-configured cyclic olefins 6 and 21 were characterized by X-ray crystallography. (C) 2004 Elsevier Ltd. All rights reserved.