A novel method for the preparation of N,N′-disubstituted-N′′-nitroguanidines, including a practical synthesis of the neonicotinoid insecticide clothianidin

A novel method is described for the synthesis of N,N′-disubstituted-N′′-nitroguanidines 3 via 2-nitroimino-hexahydro-1,3,5-triazine intermediates 12, allowing the introduction of the heteroarylmethyl group either from a heteroarylmethyl amine 9 or a heteroarylmethyl chloride 14, respectively. This method enables an efficient synthesis of the neonicotinoid insecticide clothianidin (3b) in four steps from S-methyl-N-nitroisothiourea (10).