Enolates Fischer carbene complexes react

In addition to reactions characteristic of carbonyl compounds, Fischer-type carbene complexes undergo a series of transformations which are unique to this class of compounds. These include olefin metathesis [206,265-267] (for the use as metathesis catalysts, see Section 3.2.5.3), alkyne insertion, benzannulation and other types of cyclization reaction. Generally, in most of these reactions electron-rich substrates (e.g. ynamines, enol ethers) react more readily than electron-poor compounds. Because many preparations with this type of complex take place under mild conditions, Fischer-type carbene complexes are being increasingly used for the synthesis [268-272] and modification [103,140,148,273] of sensitive natural products. 

From a methodological point of view, it should be pointed out the formation of 51, which is a result of the addition of acetone to an allenylidene ligand. Heteroatom-containing cyclic metal-carbene complexes [24] have been conveniently prepared via metal co-haloacyl, carbamoyl, alkoxycarbonyl, or imido intermediates [25], opening of epoxides by deprotonated Fischer-type carbene complexes [26], and activation of homopropargylic alcohols with low-valent d complexes [27], including ruthenium(II) derivatives [28]. In general, the preparation of unsaturated cyclic carbene complexes requires the previous preparation of functional carbenes to react with P-dicarbonyl derivatives, acrylates, and enol ethers [29]. 

Lithium enolates 56 react with Fischer alkenyl carbene complexes 55 through a 1,2-addition to give five-membered carbocycles 59 and 62 with high diastereoselectivity... 

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