Grubbs’ ruthenium catalyst

Ring-closing metathesis on the dienes 116 and 117 with Grubbs ruthenium catalyst II 18 afforded the 7-membered ring sulfones 118 and 119 respectively. The diene precursor 116 was accessed from reaction of the sulfonyl chloride 115 with 3-buten-l-ol 114 <06T9017>. 

About the same time, we published our own results on the cross-metathesis of the amino acid homoallylglycine using the Grubbs ruthenium catalyst 17 [42]. Both styrene and oct-l-ene were successfully cross-metathesised with protected homoallylglycine to give the desired products in moderate to good yields (Eq. 24). 

The most widely used catalysts for RCM are Grubbs ruthenium catalyst 9 and its second generation analogue 10, as well as first and second generation Hoveyda-Grubbs catalysts 11 and 12 (Fig. 6) [38]. The latter have superior stability and reactivity, expanding the applicability of the method considerably. Schrock molybdenum catalyst 13 has also been described for macrocy-clization [38]. 

Plumet et al. described domino metathesis of propargyl (2-endo-7-oxanorborn-5-enyl) ethers 62a-62c with allyl acetate in the presence of Grubbs ruthenium catalyst Ic (Scheme 22). The reaction proceeds stereoselectively to produce substituted m-fused bicyclic ethers 63a-63c. In a similar manner, indolizidinone derivative 64 is obtained from compound 62d instead of pyrrolizidine derivative 63d. ... 

Other examples of the same kind are syntheses of monocyclic <1997JOC7548> and 6,7,6-membered tricyclic <1997SL980> ethers (Scheme 22), Grubbs ruthenium catalyst [(Ct.Hn )3P]TTRu=CHPh being used in both cases. 

Ring closing metathesis using Grubbs ruthenium catalyst has also been used in a novel preparation of the Fischer-type chromium carbene complex 10 from the precursor 9 in >98% yield [01SL757], Similarly, the TV-substituted tetrahydroazepine 12 could be accessed in near quantitative yield from 11 [01JOC3564],... 

This approach would neither be possible, nor conceivable, without the advent of modern olefin metathesis catalysts. Figure 3 shows a few of the most commonly used catalysts. In this work, we initially relied upon Schrock s Molybdenum catalyst 6 (7) to effect the ring closures, but now exclusively rely upon the second generation Grubbs ruthenium catalyst 7 (8). 

Oxathiin 2,2-dioxides (sultones) (e.g., 150) are obtained by the addition of sulfur trioxide to dienes or by ringclosing metathesis (RCM) of sulfonates using the second-generation Grubbs ruthenium catalyst (Scheme 75) . The same catalyst was also successfully employed in the RCM of diallyl disulfide 151 which led quantitatively to 3,6-dihydro-l,2-dithiin 152 (Scheme 76) <20020L1767>. 

An enyne metathesis approach to pyrrole-2-phosphonates was reported <07CEJ203>. Treatment of enyne amine 10 with a second-generation Grubbs ruthenium catalyst in the presence of the oxidant tetrachloroquinone (TCQ) gave pyrrole-2-phosphonate 11. 

Scheme 2. Covalent capture of a self-assembled cyclic peptide dimer using the Grubbs ruthenium catalyst.

Although olefin metathesis found its genesis in the 1960s, it was not until the 1990s with the advent of Schrock s molydbedum and Grubbs ruthenium catalysts that the utility of this transformation become apparent. 

The olefin metathesis story started with the advent of well-defined catalysts, most notably the Grubbs ruthenium catalysts.These are ruthenium carbenes that undergo a [2 + 2] cycloaddition to olefins to produce a metallacyclobutane intermediate. Cycloreversion of the metallacyclobutane in the opposite sense leads to olefin metathesis (Scheme 1.35). 

Transformation of aldehydes 8 and ent-% into conduritols and inositols was achieved in a few steps via dienes 34 and 35. Conduritols B and F were easily obtained, after separation, by a RCM with the first-generation Grubbs ruthenium catalyst [46]. Syntheses of myo-inositol and c/ifro-inositol were achieved in a few further steps in good yields. Similarly, both enantiomers of cyclophellitol were synthesized from 2,3,4-tri-O-benzyl-D-xylopyranose according to the same strategy... 

CF3)2MeCO)]2(ArN)-M=CH( -Bu), where M = Mo and W [3] and Grubbs ruthenium catalyst - RuCl2(=CHPh)(PCy3)2 [4]. ADMET of silicon-containing dienes such as dialkenylsilanes and siloxanes (except vinyl derivatives), furnishes a variety of unsaturated homopolymers including carbosilanes [5] and carbosiloxanes [6] units (equation 1). 

---