New methodologies for the preparation of porphodimethenes and their conversion to trans-porphyrins with functionalized naphthyl spacers

The MacDonald [2 + 2]-type condensation of readily available 5-aryl-substit uted dipyrromethanes with acenaphthenequinone leads to the trans-syn- and a nti-porphodimethenes, which in turn can be converted to the alpha,alpha- an d alpha,beta -porphyrin atropisomers, respectively. Treatment of the metala ted or unmetalated porphodimethenes with KOH or NaOMe in THF followed by pr otonation with HCl results in a ring opening of the acenaphthenone and form ation of the trans-8-carboxynaphthylporphyrins or their esters (NaOMe) afte r oxidation. Alternatively, the porphyrin formation can be accomplished by reaction of the porphodimethenes with acids in the presence of water or met hanol. Reaction with NaBH4 in a THF-methanol mixture yields the correspondi ng dialcohols in nearly quantitative yields. Sixteen different building blo cks were prepared in order to evaluate the generality of this new synthetic approach, with Ar = 2,4,6-Me3C6H2; 2,6-Cl2C6H3; 2,6-F2C6H3; 3,4-tBu(2)C(6) H(3); 3,4,5-(MeO)(3)C6H2; 4-BrC6H4; 4-MeC6H4; and 4-MeOOCC6H4 at the meso p ositions. The synthesized porphodimethenes and porphyrins have been fully c haracterized, and the X-ray structure analyses of three representative deri vatives are presented.