Kornblum

With alkali cyanides, a reaction via a SN2-mechanism takes place the alkyl halide is attacked by cyanide with the more nucleophilic carbon center rather than the nitrogen center, and the alkylnitrile is formed. In contrast, with silver cyanide the reaction proceeds by a SnI-mechanism, and an isonitrile is formed, since the carbenium intermediate reacts preferentially with the more electronegative center of the cyanide—i.e. the nitrogen (Kornblum s rule, HSAB concept). ... 

The present preparation illustrates a general and convenient method for the fnms-iodopropenylation of an alkyl halide.4 The iodopropenyl-ated material is not usually stable but is a useful synthetic intermediate. For example, it forms a stable crystalline triphenylphosphonium salt for use in the Wittig reaction, and under Kornblum reaction conditions (DMS0-NaHC03, 130°, 3 minutes) it gives an (E)-a,/9-unsaturated aldehyde.4 In addition to the phosphonium salt described in Note 15, the following have been prepared (4-p-methoxyphenyl-2-butenyl)-triphenylphosphonium iodide [Phosphonium, [4-(4-methoxyphenyl)-2-butenyl]triphenyl-, iodide], m.p. 123-127° (2-octenyl)triphenyl-phosphonium iodide [Phosphonium, 2-octenyltriphenyl-, iodide], m.p. 98° and (2-octadecenyl)triphenylphosphonium iodide [Phosphonium, 2-octadecenyltriphenyl-, iodide], m.p. 50°. 

In general, however, reduction by ethanol is recommended only in cases where one has a reliable analytical method for distinguishing between products resulting from hydrogen- or ethoxy-substitution. For all other cases we recommend Kornblum s dediazoniation in an aqueous solution of hypophosphorous acid, in some cases in the presence of a catalyst, e.g., 0.05-0.10 mol% CuS04. The procedure is notable for its simplicity of operation. In Organic Syntheses the diazotization and hydro-de-diazoniation of 3,3 -dimethyl- and 3,3 -dimethoxybenzidine are described by Kornblum (1955) and the formation of 2,4,6-tribromobenzoic acid by Robison and Robison (1963). 

N. Kornblum, in The Chemistry of Amino, Nitroso and Nitro Compounds and their Derivatives (Ed. S. Patai), Suppl. F, Wiley, New York, 1982, p. 361. 

Herbert E. Johnson Willard J. Jones Jane Klinck Nathan Kornblum M. E. Kuehne... 

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