FIELD: organic synthesis. SUBSTANCE: aldehyde having common formula RCOH where R is lower alkyl, phenyl optionally substituted by halogen, furyl, optionally substituted by halogen or phenyl ethynyl group are affected by treatment with sodium peroxide. Said treatment is carried out in the medium of N, N-dimethylformamide or N,N-dimethylacetamide at 15-20 C. Thus obtained reaction mixture is treated by carbon dioxide and then by halogenated alkyl having formula R1X where R1 is (C1-C4) alkyl, X is atom of bromine or bromine. The process takes place within 24 h at 15-20 C, molar ratio of aldehyde, sodium peroxide and halogenated alkyl being 1.0:1.0:1.1 respectively. EFFECT: improves efficiency of the method. 1 tbl
