Dimethyl sulphate purification

The synthesis of a molecule containing two 5,5 -disubstituted-2,2 -bipyridyl units was achieved by the reaction of two equivalents of 5-bromomethyl-5 -methyl 2,2 -bipyridine (1) [11] with N,N -dimethylethylene diamine (2) in acetonitrile using potassium carbonate as base. Purification by column chromatography on alumina, using CH Cl /MeOH (99 1) as eluent, and recrystallisation from acetonitrile afforded (3) in 43% yield (Scheme 1). Reaction of (3) with dimethyl sulphate at 75 C for 7 days gave a mixture of products that were not fully methylated. Following conversion to the hexafiuorophosphate salts, this mixture was reacted further with methyl iodide in acetonitrile at reflux for 18 days. After this tii e the product was isolated and converted to the hexa-hexafluorophosphate salt to give L in 11% overall yield (Scheme 1). 

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