Porphyrin architectures bearing functionalized xanthene spacers.
A modular synthetic strategy for the construction of cofacial porphyrin architectures bearing hydrogen-bond synthons on a xanthene platform is presented. The convergent approach is based on a xanthene aldehyde-ester building block that is easily obtainable on a multigram scale with minimal purification. Treatment of this xanthene derivative with a variety of aryl aldehydes and pyrrole under standard Lindsey conditions affords a family of meso-substituted porphyrins bearing a single functionalized xanthene spacer. Direct modification of the hydrogen-bond synthon after macrocyclization proceeds smoothly to furnish porphyrin systems with a variety of cofacial functionalities (e.g., carboxylic acid, ester, amide). Porphyrins bearing two trans-functionalized xanthene spacers are prepared by the MacDonald [2 + 2] condensation of the xanthene aldehyde-ester with readily available 5-aryl-substituted dipyrromethanes such as 5-mesityldipyrromethane to afford the pure alpha,alpha- and alpha,beta-porphyrin atropisomers after chromatographic separation. The versatility of this synthetic method offers intriguing opportunities for the use of these and related templates for the study of proton-coupled activation of small molecules.
Chang
Christopher J
CJ
Department of Chemistry, 6-335, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Yeh
Chen-Yu
CY
Nocera
Daniel G
DG
D002384:Catalysis; D002845:Chromatography; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D014966:Xanthenes / Q000737:chemistry*
D011166:Porphyrins; D014966:Xanthenes