(E)-Cycloalkenes and (E,E)-cycloalkadienes by ring closing diyne- or enyne–yne metathesis/semi-reduction
摘要:
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.
A chemo- and stereoselective reduction of cycloalkynes to (E)-cycloalkenes
作者:Alois Fürstner、Karin Radkowski
DOI:10.1039/b207169j
日期:——
A stereoselective entry into (E)-cycloalkenes is described, comprising the ring closing alkyne metathesis (RCAM) of suitable diynes, a ruthenium-catalyzed trans-selective hydrosilylation of the cycloalkynes thus formed, followed by a desilylation of the resulting vinylsilanes mediated by AgF.