496041-83-9Relevant academic research and scientific papers
Alkyne metathesis: Development of a novel molybdenum-based catalyst system and its application to the total synthesis of epothilone A and C
Fuerstner, Alois,Mathes, Christian,Lehmann, Christian W.
, p. 5299 - 5317 (2001)
Sterically hindered molybdenum(III) amido complexes of the general type [Mo{(tBu)(Ar)N}3] (1), upon treatment with CH2Cl2 or other halogen donors, have been converted into highly effective catalysts for all kinds of alkyne metathesis reactions. Although the actual nature of the propagating species formed in situ is still elusive, halogen transfer to the Mo center of 1 plays a decisive role in the activation of such precatalysts. It was possible to isolate and characterize by X-ray crystallography some of the resulting molybdenum halide derivatives such as 15, 16 and 20 which themselves were shown to be catalytically active. Numerous applications illustrate the performance of the catalytic system 1/CH2Cl2 which operates under mild conditions and tolerates an array of polar functional groups. The wide scope allows the method to be implemented into the total synthesis of sensitive and polyfunctional natural products. Most notable among them is a concise entry into the potent anticancer agents epothilone A (86) and C (88). The macrolide core of these targets is forged by ring closing alkyne metathesis (RCAM) of diyne 113, followed by Lindlar hydrogenation of cycloalkyne 114 thus formed. Since this strategy opens a stereoselective entry into (Z)-alkene 115, the approach is inherently more efficient than previous syntheses based on conventional RCM. Wiley-VCH Verlag GmbH, 2001.
(E)-Cycloalkenes and (E,E)-cycloalkadienes by ring closing diyne- or enyne-yne metathesis/semi-reduction
Lacombe, Fabrice,Radkowski, Karin,Seidel, Günter,Fürstner, Alois
, p. 7315 - 7324 (2007/10/03)
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)3WCCMe3 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.
