Phosphonium amalgam iodide

When the reactions of pyrroles and indoles with aldehydes are catalyzed by hydriodic acid, the initially formed carbinols or azafulvenes are reduced to yield the corresponding alkylpyrroles and alkylindoles (68CJC3291,70CJC139). The reductive alkylation of the pyrrole ring, using a range of aliphatic and aromatic aldehydes and ketones, may also be accomplished with phosphonium iodide, with hydrochloric acid and zinc amalgam, or with tin(II) bromide in hydrobromic acid. 

ALKENES Calcium amalgam. N,N-Dimethylformamide dimethyl acetal. N,N-Methylphenylaminotriphenyl-phosphonium iodide. N,N,N, NrTetra-methyldiamidophosphorochloridate. Titanium(O). p-Toluenesulfonylhydra-zine. Tii-n-butyltin hydride. Triphenyl-phosphine-Diethyl azodicaiboxylatc. Trityl tetrafluoroborate. 

Baeyer had previously introduced the important method of reduction by heating with zinc dust. He used phosphonium iodide (a good method of preparation of which he described) instead of hydriodic acid and red phosphorus (Berthelot s method) in reductions. He carried out a long research on the reduction of phthalic, isophthalic, and terephthalic acids with sodium amalgam, the results being used in elucidating the structure of benzene (see p. 804). Isophthalic acid derivatives were synthesised by O. Doebner. ... 

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