Hydroformylation and hydrocarbethoxylation of 1,2-dicarbethoxy-1,2,3,6-tetrahydropyridazine and 1,2-dicarbethoxy-1,2,3,4-tetrahydropyridazine

The unsaturated compounds 1,2-dicarbethoxy-1,2,3,6-tetrahydropyridazine 1 and 1,2-dicarbethoxy-1,2,3,4-tetrahydropyridazine 2 have been hydroformylated and hydrocarbethoxylated in the presence of some well known cobalt, rhodium, palladium and platinum catalysts. The hydroformylation reaction can be tuned by a suitable choice of the catalyst precursor and reaction conditions, thus allowing the synthesis with high selectivity of one of the two possible isomeric aldehydes. The carbonylation reaction is less synthetically useful, since it shows low activity and unsatisfactory chemo- and regio-selectivity. However, the ester 1,2,4-tricarbethoxyhexahydropyridazine 10 can be prepared in good yield from olefin 1 by using the complex [PdCl₂(PPh₃)₂] as the catalyst precursor.