The reaction of various alpha-silyl-alpha-keto esters with thiosemicarbazide at 50 degrees C in ethyl acetate was found to give alpha-silyl-substituted thiosemicarbazone-acetic acid esters in good yield. These may then be converted to their corresponding silyl-substituted 1,2,4-triazin-5-ones by cyclization under basic conditions. (c) 2005 Elsevier Ltd. All rights reserved.