Tandem hydroformylation-Fischer indole synthesis

Relying on a tandem hydroformylation/Fischer indole synthesis, a number of indoles possessing various substituents at C-3 and/or C-5 were prepared in moderate yields. Thus for example, the tryptamines 98 were produced from hydrazines 99 and the methallylic phthalimide 100 <03OL3213>. 

A novel rhodium-catalyzed one-pot synthesis of indole systems via tandem hydroformylation-Fischer indole synthesis starting from olefins and arylhydrazines was described. The procedure leads directly to 3-substituted indoles if unsubstituted phenylhydrazine is used. Using para- or ortho-substituted arylhydrazines, the corresponding 3,5- and 3,7-disubstituted indoles are formed, respectively [160]. 

The tandem hydroformylation-Fischer indolization protocol was used in the synthesis of 2,3-disubstituted indoles. Several olefins, bearing substituents with various functional groups, as well as cyclic olefinic systems were investigated (Equations 7.20 and 7.21)... 

With this tandem hydroformylation/hydrazone formation/Fischer indolization 3-substituted indoles such as valuable intermediates for the synthesis of pharmaceuticals as well as pharmaceuticals can be obtained in a very... 

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