Ruthenium-catalyzed ring-closing olefin metathesis

B. Ruthenium-Catalyzed Ring-Closing Olefin Metathesis... 

A similar type of cascade reaction has been carried out with cyclic alkenes bearing only one olefinic side chain to obtain substituted heterocycles via ruthenium-catalyzed ring closing-ring opening metathesis (RCM-ROM) reactions. The preparation of enantiomerically pure cis- or trans-a,a -disubstituted piperidines has been achieved in the same yield for the two diastereoisomers [35] (Scheme 17). This reaction has also been used as a key step for the synthesis of natural products [36-39]. 

Berlin JM, Campbell K, Ritter T, Funk TW, Chlenov A, Grubbs RH. Ruthenium-Catalyzed Ring-Closing Metathesis to Form Tetrasubstituted Olefins. Org Lett. 2007 9(7) 1339-1342. 

In 1998, Grubbs and coworkers published an a-helix stabilization attempt through 0-allyl serine residues located on adjacent helical turns, via ruthenium-catalyzed ring closing metathesis (RCM) [56] unfortunately, this study did not result in enhanced a-helical structure stabilization. Subsequently, Verdine and coworkers advanced this idea by introducing two alpha-olefin substituted... 

The synthesis and olefin metathesis activity in protic solvents of a phosphine-free ruthenium alkylidene bound to a hydrophilic solid support have been reported. This heterogeneous catalyst promotes relatively efficient ring-closing and cross-metathesis reactions in both methanol and water.200 The catalyst-catalyzed cross-metathesis of allyl alcohol in D20 gave 80% HOCH2CH=CHCH2OH. 

Ruthenium-catalyzed olefin cross-metathesis (ring-closing metathesis, RGM) between terminal alkenes and vinyl-boronic acid or esters has recently been developed for the synthesis of ( )-l-alkenylboron compounds from alkenes.459,460 The efficiency of protocol was proved in the synthesis of a key intermediate of epothilone 490 292 461 (Equation (84)). The vinyl boronate was given almost exclusively the trans-adduct. 

Recently, it was shown that bis(tricyclohexylphosphine)benzyhdene ruthenium dichloride (101) [120, 121] is also capable of catalyzing olefin metathesis on a sohd support [122], Thus, performing the reaction as ring-closing metathesis offers an-... 

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