NOVEL PORPHYRINOIDS .14. BIOMIMETIC SYNTHESES OF DOUBLY N,N'-BRIDGED [18]PORPHYRINOGENS

Six N,N'-alkylene-bridged bispyrroles 9a-9e and one N,N'-oxaalkylene-b ridged bispyrrole 16 with a reactive group at C-1 of each pyrrole unit were synthesized in 53-78% yields. Acid-catalyzed ''biomimetic'' cond ensations of the bispyrroles with N,N'-C3 to N,N'-C, bridges yielded N ,N':N'',N''' doubly bridged porphyrinogens 14, 15, 17, 18, which are n ovel heterocyclic systems. By exchanging one CH2 group for oxygen in t he N,N'-alkylene chain of ge to reduce the Prelog strain, the condensa tion yield was significantly increased. The N,N'-C1- and the N,N'-C2-b ridged bispyrroles 9a, 9b did not cyclize to porphyrinogens, but in on e case cyclized to give a N,N'-C1-bridged dipyrrylmethane 12 instead.