130611-86-8Relevant academic research and scientific papers
Porphyrins with exocyclic rings. Part 22: Synthesis of deoxophylloerythroetioporphyrin (DPEP), three ring homologues, and five related nonpolar bacteriopetroporphyrins using a western ring closure and an improved b-bilene methodology
Lash, Timothy D.,Li, Wei,Quizon-Colquitt, Desiree M.
, p. 12324 - 12342 (2007)
Dipyrrolic intermediates incorporating five-membered carbocyclic rings are easily prepared from cyclopenta[b]pyrroles, and this unit represents the southern half of the DPEP-type geoporphyrins found in organic-rich sediments such as oil shales and petroleum. Related dipyrroles with six-, seven- or eight-membered carbocyclic rings were shown to give b-bilenes when reacted with dipyrrylmethane carbaldehydes under mildly acidic conditions. Following deprotection of the terminal ester groups, cyclization with TFA-CH(OMe)3 gave a series of ring homologues of deoxophylloerythroetioporphyrin (DPEP). The b-bilenes generated from the five-membered ring dipyrroles proved to be rather unstable and had to be used directly without purification. Cyclization gave DPEP contaminated with an etioporphyrin by-product, but these could be separated as the nickel(II) derivatives by flash chromatography. This approach gave superior yields of DPEP compared to previously reported methods. In addition, the methodology could be extended to the synthesis of related petroporphyrins, and a series of five molecular fossils derived from bacteriochlorophylls d were synthesized by this approach.
Porphyrins with exocyclic rings. Part 12. Synthesis of meso,β-butano- and meso,β-pentanoporphyrins from cycloalka[b]pyrroles
Bastian, Jolie A.,Lash, Timothy D.
, p. 6299 - 6310 (2007/10/03)
Pyrroles 5 with b-face fused seven- or eight-membered carbocyclic rings were prepared in good yields by Knorr-type condensations with cycloheptanone or cyclooctanone, respectively. Treatment with lead tetraacetate in dichloromethane afforded the labile ω-acetates 8 and subsequent acid catalyzed condensation with α-unsubstituted pyrrole-2-carboxylates yielded the related pyrrolylcycloalka[b]pyrroles 29 and 30. The α-unsubstituted pyrroles 14 and 23 were prepared by condensing α,β-unsubstituted ketones, or their β-acetoxycarbonyl precursors, with benzyl N-tosylglycinate in the presence of DBU, followed by dehydration with POCl3-pyridine and base catalyzed elimination of p-toluenesulfinic acid. Dipyrrole dibenzyl esters 29 and 30 were hydrogenolysed over 10% Pd-C to give the corresponding dicarboxylic acids. Acid catalyzed condensation with diformyldipyrrylmethane 33 under modified MacDonald '2 + 2' conditions afforded a series of four cycloalkanoporphyrins 4a-d with seven- or eight-membered exocyclic rings. Although the meso,β-butanoporphyrins 4a and 4b were isolated in good yields, poorer results were obtained for the related meso,β-pentanoporphyrin: 4c and 4d. It is proposed that the eight-membered carbocyclic ring distorts the geometry of the open-chain tetrapyrrolic intermediates and this deleterious influence results in the lower yields observed.
