... Volume: Page: ... In the 13 C NMR spectrum, the formyl-C and 6-C of 2a were indicated at 184.6 and 145.6 ppm, respectively ... The Vilsmeier-type reaction was further utilized for the synthesis of spiro or substituted pyridine-2,4(1H,3H)-diones 3 from 1-aminoalkenoyl ...