Organochromium carbenes

A more elaborate organochromium method for the generation of 1-substituted isobenzofurans was also reported. As can be seen below, treatment of the o-alkynylbenzaldehyde with the Fischer chromium carbene complex provides the isobenzofuran-Cr(CO)3 complex 128 which can be trapped by the electron-deficient Ai-phenylmaleimide with excellent exo-selectivity. . 

Organoboration, of iminoboranes, 31 155-156 Organoboron alJcyls, 2 75 Organochromium alkyl compounds, 44 354-357 carbenes, 44 352-354 compounds, 44 344... 

Fig. 7. Synthesis of dipeptides using organochromium(O) carbenes ( indicates known chiral center indicates a new chiral center).

Organochromium reagents have found varied use in organic synthesis. Aryl-chromium complexes influence significantly the reactivity of the aromatic ring and have been used widely. Other unsaturated chromium complexes, alkyl-chromium species and chromium carbenes promote useful transformations and continue to attract attention. 

The other reason is that organochromium compounds are able to be formed by carbene complexes and the reaction of the carbene complexes are available. 

Organochromium compounds are able to easily form stable carbene complexes as described in the above section [70-75]. The representative method is as follows hexacarbonylchromium reacts with a nucleophile to give an acylanion, then the chromium carbene is prepared by alkylation of the acyloxygen with a trialk-yloxonium salt or a diazomethane as shown in eq. (13.39). As this reaction was... 

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