The rational synthesis of chlorins via rearrangement of porphodimethenes: influence of beta-substituents on the regioselectivity and stereoselectivity of pyrroline ring formation

No Thumbnail Available
Authors
Burns, Dennis H.
Li, Yue He
Shi, Dong C.
Caldwell, Timothy M.
Issue Date
2002-06-28
Type
Article
Language
eng
Keywords
Research Projects
Organizational Units
Journal Issue
Alternative Title
Abstract

The porphodimethene rearrangement methodology reported in this paper provides for a rational, step-by-step synthesis of chlorins from readily available pyrrole precursors. The intermediate porphodimethenes are furnished directly via the '2 + 2' MacDonald condensation, or by the less symmetry-constrained '3 + 1' condensation of a tripyrrane and bis-formyl pyrrole. The synthetic route is short and highly convergent, especially in the case of the '3 + 1' approach, and furnishes chlorins in good to moderate yields. The synthesis is highly regioselective and appears to be based on the ability of the beta-substituent to stabilize excess electron density, with an electron-neutral hydrogen or an electron-withdrawing carbonyl beta-substituent demonstrating the greatest influence on the formation of the pyrroline ring. The synthesis is highly stereoselective when epimerization of the pyrroline ring beta-carbons is possible, furnishing only the trans-reduced sterioisomer. Finally, there is substantial evidence that a fifth, axial ligand is involved in the transposition of peripheral hydrogens during the rearrangement of the pi-system from metalloporphodimethene to metallochlorin.

Description
Full text of this article is not available in SOAR.
Citation
The Journal of organic chemistry. 2002 Jun 28; 67(13): 4536-46.
Publisher
American Chemical Society
License
Journal
Volume
Issue
PubMed ID
DOI
ISSN
0022-3263
EISSN