New synthetic routes to porphyrins and bacteriochlorins

Porphyrinic macrocyclic compounds which have an 18-pi-electron-conjugated system include porphyrins, chlorins (dihydroporphyrins), and bacteriochlorins (tetrahydroporphyrins). Changes in the reduction level are reflected by changes in the absorption spectra of these macrocycles. Such changes also alter the physical and chemical properties of these compounds in biological systems. Therefore, the synthesis and studies of the porphyrinic molecules are relevant to various applications in the life sciences and materials chemistry.;This dissertation describes synthetic approaches to two classes of porphyrinic macrocycles, trans-AB porphyrins and bacteriochlorins. In the synthesis of trans-AB porphyrins (chapter II and III), two rational routes have been extensively studied. Each route employs dipyrromethane species. The first method studies the (N,N-dimethylamino) methylation of dipyrromethanes with Eschenmoser's reagent followed by condensation of the resulting 1,9-dialkylated dipyrromethane with a dipyrromethane to form the trans-AB porphyrin. The second method focuses on the use of imine groups as one-carbon synthons in the preparation of trans-AB-porphyrins. The studies involve the 1,9-diformylation of dipyrromethanes, imination of the 1,9-diformyldipyrromethanes, and condensation of the resulting bis-imine with a dipyrromethanes to give the trans -AB porphyrin.;The synthesis of bacteriochlorins spans three chapters. (1) Several new bacteriochlorin derivatives were obtained from the regioselective 15-bromination of a stable synthetic bacteriochlorin followed by palladium-mediated coupling reactions. The resulting bacteriochlorins contain ethyne, aryl, or a benzamido group at the 15-position. (2) Four metallobacteriochlorins incorporating a divalent metal (Zn, Cu, and Pd) or a trivalent metal (In) have been obtained by treatment of the free base bacteriochlorin H2BC with a base followed a metal salt. (3) The synthesis of beta-alkylbacteriochlorins was explored via the self-condensation of alkyl-substituted hydrodipyrrins. Applications for these newly available bacteriochlorins include fundamental studies, medicinal diagnostics and treatment of disease, dye-sensitized solar cells, and potential substrates as self-assembling materials.