Fischer carbene complexes, cyclic synthesis

A very rapid growth of novel and synthetically useful reactions of Fischer-type carbene complexes see Fischer type Carbene Complexes has occurred over the last decade. Reactions leading to cyclic and polycyclic compounds of high complexity and reactions wherein chirality has been transferred from the starting material to the product are of particular importance. A number of recent reviews on the chemistry of Fischer carbene complexes and their application in organic synthesis are available. 

In 1994, Quayle et al. reported the application of this cyclic Fischer-carbene synthesis from 3-butynols to spirolactone synthesis, although the process was stepwise and a stoichiometric amount of the complex was employed [17]. The key transformation was the chromium or tungsten carbene complex formation followed by the CAN oxidation of the complex to give y-lactone. The reaction was further applied to the synthesis of andirolactone and muricatacin, the former being shown in Scheme 5.14. 

The cyclic carbene complex (23) formed in equation 10.722 is analogous to the original Fischer-type carbene complex. The ring, however, offers an added complexity that has utility in the realm of organic synthesis. 

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