Cross-Metathesis CM of Diene

Entry Olefin a-Functionalized Olefin Product Yield (%) (Ratio) 

The cross-metathesis of terminal alkenes and functionalized alkenes is shown in Table 6.2. In each case, a CM product is obtained in high yield and an -isomer is formed predominantly.  

In traditional synthetic organic chemistry, the Wittig reaction plays an important role in carbon-carbon bond extension from the carbonyl group. CM is an attractive alternative for carbon-carbon extension from a terminal alkene. In fact, a pyrroh-dine ring of anthramycin derivative 55 has been constructed by RCM of 52, and the sidechain has been extended by CM of terminal alkene of 54 with ethyl acrylate. In the CM, ruthenium carbene complex Ij, reported by Blechert, gives a good result since the ligand of the catalyst easily dissociated from the ruthenium metal at room temperature  

3 Ring-Opening Metathesis (ROM)-Ring-Closing Metathesis (RCM) of Alkene 

As an application of this procedure, Snapper succeeded in the formal total synthesis of (+)-astericanolide. Treatment of iron complex 62, which is prepared from cyclopentenol derivative 60 and iron complex 61, with MeaNO gives fused cyclobutene derivative 63. ROM of cyclobutene of 63 using Ig under ethylene gas smoothly proceeds to produce an eight-membered ring of 64 via Cope rearrangement. The resulting product 64 is converted into Wender s intermediate for the synthesis of (+)-astericanolide  

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