Keywords: Michael reaction, 3-ethoxycarbonyl(acyl)coumarins, malonic acid dihydrazide, N'-salicylidene derivatives of coumarin-3-carboxylic acid, lactonc ring opening.Earlier we established that reaction of 3-ethoxycarbonyl(acyl)coumarins with cyanoacetylhydrazine and its N-derivatives under Michael reaction conditions leads to synthesis of 3-cyanocoumarins [1,2]. In an extension of this research, under similar conditions (ethanol, 70-75~ catalytic amounts of piperidine), we have studied the reaction of 3-cthoxycarbonyl-, 3-acetyl-, and 3-benzoylcoumarins la-c and also their 6-methyl-and 6(8)-methoxysubstituted derivatives ld-i with malonic acid dihydrazide 2. We have established that N'-salicylidene derivatives of coumarin-3-carboxylic acid hydrazide 3a-c are formed as a result of this reaction.R 4 R 4 3a.-r la R = OC2H5, R ~a = H; lb R = CH 3, R Ia = H; lc R = C6H5, R TM = H; ld R = OC2H5, R 3 = CH3, R 1"2'~ = H; le R = R e = CH3, R 1'3'4 = H; lfR = CrHs, R 2 = CH3, R 1"3"4 = H; lg R = OC2Hs, R 4 = OCH3, R t'2"3 = H; lh R = CH3, R 4 = OCH3, R t'2'3 = H; 1i R = C6H5, R 4 = OCH3, R 1'2'3 = H; 3a R t4 = H; 3b R 2 = CH3, R 1'2'3 = H; 3c R 4 = OCH3, R 1'2'3 = H D. I. Mendeleev Russian