Dichloromethylene dimethylammonium

Dichloromethylene) -dimethylammonium chloride (Vilsmeier reagent/Viehe s salt)... 

The reaction of enamines with iminium ions provides access to substituted j3 amino aldehydes and ketones (Scheme 61). In a similar manner the Mannich reaction gives access to oc,) -unsaturated aldehydes or -amino ketones (Scheme 62). Enamines undergo the Vilsmeier reaction to give a-formyl ketones Solvolysis of the Vilsmeier salt with aqueous or alcoholic sodium hydrogen sulphide produces an enamino thioaldehyde. The use of A-dichloromethylene-A,A -dimethylammonium chloride gives tertiary /5-ketoamides (Scheme 63). Iminoalkylation of enamines with nitrilium salts provides access to enamino ketones and j3-diketones (Scheme 64). 

Electrophilic cyclisation onto the aromatic ring achieves the synthesis of 3-aminoindazoles when arylhydrazines are reacted with Ar-(dichloromethylene)-AT,A -dimethylammonium chloride, as shown. The formation of l-benzyl-3-hydroxyin-dazole by heating A -benzylphenylhydrazine with urea at 285 °C involves the electrophilic cyclisation of a first formed semicarbazide. ... 

Heating at reflux of dichloromethylene-iV,A -dimethylammonium chloride with diamine 147 in dioxane furnished 2-dimethylamino-IP 151 in good yield (83USP4391811). 

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