SYNTHESIS OF 8-DEMETHYL-8-FORMYL PROTOPORPHYRIN IX AND OF 8-DEMETHYL PROTOPORPHYRIN IX

Article abstract of DOI:10.1016/S0040-4020(01)89134-1

A 8-demethyl-8-formyl-2,4-bis(β-chloroethyl)porphyrin and its 8-demethyl derivative were obtained from the oxidative cyclization of 2,4-bis(β-chloroethyl)-6-(β-ethoxycarbonylethyl)-7-(β-methoxycarbonylethyl)-1',1,3,5,8-pentamethyl a,c-biladiene dihydrobromide with copper(II) chloride in dimethyl formamide (DMF) in the presence of iodine and air.Under these reaction conditions the cyclization took place at 25 deg C and the formylporphyrin was obtained in 25 percent yield together with the C-8 unsubstituted porphyrin which was obtained in 50 percent yield.The latter could also be obtained in 65 percent yield by the oxidative cyclization with copper(II) chloride in DMF at 25 deg C of the β-unsubstituted 1,7-bis(β-chloroethyl)-4-(β-methoxycarbonylethyl)-5-(β-ethoxycarbonylethyl)-1',2,6,8,8'-pentamethyl-a,c-biladiene dihydrobromide.The formylation attempts at the C-8 unsubstituted position of this porphyrin were however unsuccesful, when either N,N-diisobutyl formamide (Vilsmeier-Haak reaction) or dichloromethyl methyl ether (Friedel Crafts reaction) were used.The title porphyrins were obtained from the aforementioned 2,4-bis(β-chloroethyl) porphyrins by vinylation of the latter with base. 8-Demethyl-8-formyl protoporphyrin IX is a valuable intermediate to probe into the biosynthesis of heme a.