Different variants of the synthesis of syringaldehyde (SA), acetosyringone (AS), and propiosyringone (PS) from the respective guaiacylcarbonyl compounds according to the reactions of their halogenation in the 5-position of the ring, and the following replacement of the halogen for a OCH₃-group by CH₃ONa in the DMFA medium in the presence of CuCl₂ at 100°C, were comparatively investigated. The intermediate iod-derivatives are shown to give higher yields of SA, AS, and PS (80, 81, and 58per thousand from the initial guaiacyl compounds) with higher degree of purity than the brom-derivitives. A description of the synthesis techniques of 5-bromacetovanillone, 5-brom- and 5-iod-propiovanillone, unknown in the literature earlier, is proposed; the method for the synthesis of 5- iodacetovanillone is improved.