New methods for the selective alkylation of 3-thioxo-1,2,4-triazin-5-ones

A method for regioselective alkylation of the 3-thiono-1,2,4-triazinone 10 at the sulfur atom is reported. Subsequent Claisen rearrangements, triggered either thermally or using a palladium catalyst, deliver N-alkylated products 13, while acid-catalysed rearrangements of examples where a tertiary carbenium ion can be generated, result in the formation of N-thioalkyl derivatives.