In connection with the studies on the dehydrotive cyclization of o-hydroxyacetophenones using thionyl chloride, the reaction with various aldehydes such as salicylodehyde (1), o-vanillin (3) and 3-bramosaticylaldehyde (2) was first tried. Anhydrodisalicylaldehyde (4), anhydrodiovanillin (6) and anhydrobis (5-bramosalicylaldehyde) (5) were easily obtained from the reactions. The dimers (4) and (5) have already been described in the literature, prepared from the corresponding aldehyde with a number of dehydrating agents (1). The 13c NMR spectra of these dimers is reported here. As Is to be expected, all the dimers are symmetrical.