meso-Aryl-3-alkyl-2-oxachlorins

J Org Chem. 2012 Jul 20;77(14):6199-207. doi: 10.1021/jo300964v. Epub 2012 Jul 11.

Abstract

The formal replacement of a pyrrole moiety of meso-tetraarylporphyrin 1 by an oxazole moiety is described. The key step is the conversion of porpholactones 4 (prepared by a known two-step oxidation procedure from 1) by addition of alkyl Grignard reagent to form meso-tetraaryl-3-alkyl-2-oxachlorins 9 (alkyloxazolochlorins; alkyl = Me, Et, iPr). Hemiacetal 9 can be converted to an acetal, reduced to an ether, or converted to bis-alkyloxazolochlorins 11. The optical properties (UV-visible and fluorescence spectroscopy) are described. The chlorin-like optical properties of the alkyloxazolochlorins are compared to regular chlorins, such as 2,3-dihydroxychlorins and nonalkylated oxazolochlorins made by reduction from porpholactone 4. The conformations of the mono- and bis-alkylated 2-oxachlorins, as determined by single crystal X-ray diffractometry, are essentially planar, thus proving that their optical properties are largely due to their intrinsic electronic properties and not affected by conformational effects. The mono- and bis-3-alkyl-2-oxachlorins are a class of readily prepared and oxidatively stable chlorins.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallography, X-Ray
  • Models, Molecular
  • Molecular Structure
  • Porphyrins / chemical synthesis*
  • Porphyrins / chemistry

Substances

  • Porphyrins
  • chlorin