Octaethyl-1,3-oxazinochlorin: A β‑Octaethylchlorin Analogue Made by Pyrrole Expansion

Treatment of the oxime of octaethyloxochlorin <b>4</b>, available from octaethylporphyrin <b>3</b>, under Beckmann conditions provided not the expected lactam, but octaethyl-1,3-oxazinochlorin <b>8</b>, in which a pyrrole moiety of the parent oxochlorin was expanded by an oxygen atom to an 1,3-oxazinone moiety. Its mechanism of formation was demonstrated to occur along an “abnormal Beckmann” pathway, followed by intramolecular ring closure and hydrolysis. The work expands the methodologies known to convert octaethylporphyrin to pyrrole-modified porphyrin analogues

<i>meso</i>-Aryl-3-alkyl-2-oxachlorins

The formal replacement of a pyrrole moiety of <i>meso</i>-tetraarylporphyrin <b>1</b> by an oxazole moiety is described. The key step is the conversion of porpholactones <b>4</b> (prepared by a known two-step oxidation procedure from <b>1</b>) by addition of alkyl Grignard reagent to form <i>meso</i>-tetraaryl-3-alkyl-2-oxachlorins <b>9</b> (alkyloxazolochlorins; alkyl = Me, Et, <i>i</i>Pr). Hemiacetal <b>9</b> can be converted to an acetal, reduced to an ether, or converted to bis-alkyloxazolochlorins <b>11</b>. 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 <b>4</b>. 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

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR

<i>meso</i>-Aryl-3-alkyl-2-oxachlorins

The formal replacement of a pyrrole moiety of <i>meso</i>-tetraarylporphyrin <b>1</b> by an oxazole moiety is described. The key step is the conversion of porpholactones <b>4</b> (prepared by a known two-step oxidation procedure from <b>1</b>) by addition of alkyl Grignard reagent to form <i>meso</i>-tetraaryl-3-alkyl-2-oxachlorins <b>9</b> (alkyloxazolochlorins; alkyl = Me, Et, <i>i</i>Pr). Hemiacetal <b>9</b> can be converted to an acetal, reduced to an ether, or converted to bis-alkyloxazolochlorins <b>11</b>. 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 <b>4</b>. 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

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR

<i>meso</i>-Aryl-3-alkyl-2-oxachlorins

The formal replacement of a pyrrole moiety of <i>meso</i>-tetraarylporphyrin <b>1</b> by an oxazole moiety is described. The key step is the conversion of porpholactones <b>4</b> (prepared by a known two-step oxidation procedure from <b>1</b>) by addition of alkyl Grignard reagent to form <i>meso</i>-tetraaryl-3-alkyl-2-oxachlorins <b>9</b> (alkyloxazolochlorins; alkyl = Me, Et, <i>i</i>Pr). Hemiacetal <b>9</b> can be converted to an acetal, reduced to an ether, or converted to bis-alkyloxazolochlorins <b>11</b>. 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 <b>4</b>. 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

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR

Oxazolochlorins. 9. <i>meso</i>-Tetraphenyl-2-oxabacteriochlorins and <i>meso</i>-Tetraphenyl-2,12/13-dioxabacteriochlorins

The formal replacement of one or two pyrrole groups in <i>meso</i>-tetraphenylporphyrin by oxazole moieties is described, generating inter alia the bacteriochlorin-type chromophores oxazolobacteriochlorins (oxabacteriochlorins) and bisoxazolobacteriochlorins (dioxabacteriochlorins). The key step is the conversion of a β,β′-dihydroxy-functionalized pyrroline group into an oxazolone or (substituted) oxazole. Depending on the substitution pattern on the oxazole or oxazoline moieties, mono- and dioxabacteriochlorins may have chlorin- or bacteriochlorin-like spectra. The optical properties (as measured by UV–vis and fluorescence spectroscopies) of the novel oxa- and dioxabacteriochlorins are described and contrasted against benchmark chlorins and bacteriochlorins. The conformations of a representative number of mono- and dioxabacteriochlorins, as their free bases or Zn^II complexes, were determined by single-crystal X-ray diffractometry. They proved to be essentially planar, showing that the modulation of their optical properties is primarily due to their intrinsic electronic structures and electronic substituent effects and are not largely affected by conformational effects. The mono- and bisoxazolobacteriochlorins are a novel class of readily prepared and oxidatively stable chlorin and bacteriochlorin analogues with tunable optical spectra that, in part, reach into the NIR