Methylidene-molybdenum carbene complex

Several molybdenum-methylidene complexes 56 are employed as olefination reagents (Scheme 4.53). Some of them differ from the conventional carbonyl olefination reagents in their acidic character and chemoselectivity. Generally, molybdenum carbene complexes are thermally unstable and attempts to isolate them have hitherto been unsuccessful. Therefore, the olefinating reagents are generated in solution in the presence of the carbonyl compounds such that they react immediately. 

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