75116-24-4Relevant academic research and scientific papers
Porphyrins with Exocyclic Rings. Part 3. A Reassessment on the Utility of Cyclopentapyrroles in the Synthesis of Porphyrin Molecular Fossils. Preparation of Three Type II Porphyrins Related to Deoxophylloerythroetioporphyrin (DPEP)
Lash, Timothy D.,Catarello, James J.
, p. 4159 - 4172 (2007/10/02)
The utility of cyclopentapyrroles in porphyrin synthesis has been reinvestigated.A 6-oxocyclopentapyrrole 18 was prepared by cyclization of the propanoyl chloride sidechain of an α-unsubstituted pyrrole 17d in the presence of tin(IV) chloride.Subsequent reduction with sodium borohydride afforded the corresponding 6-hydroxy compound 10 and further acid catalyzed condensation with α-unsubstituted pyrroles 11a and 11b gave the novel 6-pyrrolylcyclopentapyrroles 22a and 22b in excellent yields.Attempts to prepare deoxophylloerythroetioporphyrin (DPEP; 2), a widespread sedimentary porphyrin molecular fossil, from these dipyrrolic intermediates using the tripyrrene-a,c-biladiene route were unsuccessful.However, the synthesis of three related meso,β-ethanoporphyrins using the MacDonald condensation was successfully carried out in moderate to good yields.Retention of an sp3 hybridized carbon bridge at the cyclopentene ring fusion site of the intermediary open chain tetrapyrroles appears to be crucial during macrocycle formation, as this diminishes the steric repulsion between the peripheral substituents and the carbocyclic ring.
The Reaction of Thioimides with Phosphorus Ylides
Bishop, John E.,O'Connell, John F.,Rapoport, Henry
, p. 5079 - 5091 (2007/10/02)
The reaction of a series of thioimides with phosphorus ylides, in a manner analogous to the Wittig reaction, has been examined.The resulting reaction products represent potentially valuable intermediates in tetrapyrrole pigment synthesis.In addition to the desired thio-Wittig-type coupling reaction, the presence of two competing reaction pathways, S-alkylation and oxidation/reduction, has been observed with certain substrates.These empirical observations have been correlated to theoretical data, derived from MNDO and ab initio calculations, which delineate the structu re-reactivity relationships governing product distribution from the various reaction pathways.A detailed analysis is presented of the mechanism of the thio-Wittig coupling reaction and the competitive S-alkylation reaction.
