The cyclisation of 1-bromo-19-methyl- and 1,19-dimethyl-1,19-dideoxybiladiene-ac dihydrobromides

Abstract

The cyclisation of 1-bromo-1,19-dideoxy-19-methylbiladiene-ac dihydrobromides (I) bearing β-alkyl substituents to porphins in presence of a variety of one-electron oxidising agents has been shown to proceed at room temperature. Cyclisation of 1,19-dideoxy-1,19-dimethylbiladiene-ac dihydrobromides can be effected by cupric salts in boiling NN-dimethylformamide for 2 minutes. The alternative cyclisation of a variety of these salts in presence of nickel or cobalt salts yields the corresponding metal 1,19-disubstituted tetradehydrocorrins (VII) which are conveniently isolated as the perchlorates. Cyclisation of the nickel complex of a 1,19-dideoxy-1,19-dimethylbiladiene-ac in presence of ammonium ceric nitrate at room temperature also gave the corresponding nickel 1,19-dimethyltetra-dehydrocorrin salt (VIII).