A Convenient and Facile Synthesis of 5-Trifluoromethyl-1,2,4-triazine Derivatives

Abtrad -3-Hydrazono-1 ,l , l -trifluoroalkan-2-ones (2) and 3-methylhydrazono-l,1,1trifluoroalkan-2-ones (3) prepared from 1 , I ,1 -trifiuoroalkane-2,3-diones (1 ) reacted with several aldehydes in the presence of aq.NH40H to afford 5-trifluoromethyl-2,3dihydro-l,2,4-triazines (4 and 5) of which oxidation gave 5-trifluoromethyl-l,2,4triazines (6) and 5-trifluoromethyl-2,5-dihydro-5-hydroxy-l,2,4-triazines (7).Thermal reaction of 5 afforded 1 -amino-4-trifluoromethylimidazoles (8).Triazine derivatives are of special interest owing to their potentially high pharmacological properties applicable to cardiotonics, antihypertensives etc.1-3In particular, fluorine-containing triazine derivatives may be fascinating target for many organic synthetic chemists.4 1 ,l , l -Trifluoroalkane-2,3-dione monohydrates (1) which are readily obtainable from a varieties of aldehydes by our three-steps methods may be one of the most useful intermediates accessible to fluorinecontaining 1,2,4-triazine derivatives.This prompted us to try synthesis of 5-trifluoromethyl-l,2,4triazine derivatives from 1. Now we wish to report the results.By usual method,s trifluoroacetylation of aldehyde dimethylhydrazones with the use of