Hydrogen-Bonded Double Strands: Crystal Structure and Spectroscopic Propertiesof a 2,2′-Dipyrryl Ketone

Huggins, Michael T.; Tipton, Adrianne K.; Chen, Qingqi; Lightner, David A.

doi:10.1007/s007060070060

Cited by 9 publications

(4 citation statements)

References 4 publications

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“…For example, where the carbonyl is syn to the pyrrole NH, as in tert-butyl 2-pyrryl ketone the NH chemical shift is 9.5 ppm, but where the carbonyl group is anti, as in tert-butyl 2-(3,4-dimethyl pyrryl) ketone it is ∼1 ppm more shielded, to 8.6 ppm. 22 Molecularity in Solution. To assess whether 1-4 are monomeric in CHCl 3 solution, we determined their molecular weights by vapor pressure osmometry (VPO) over a molal concentration range 1.7-6.1 × 10 -3 .…”

Section: Resultsmentioning

confidence: 99%

“…One may find a parallel for the dependence of the NH chemical shift on the orientation of the ketone carbonyl group in certain pyrryl ketones. For example, where the carbonyl is syn to the pyrrole NH, as in tert -butyl 2-pyrryl ketone the NH chemical shift is 9.5 ppm, but where the carbonyl group is anti, as in tert -butyl 2-(3,4-dimethyl pyrryl) ketone it is ∼1 ppm more shielded, to 8.6 ppm …”

Section: Resultsmentioning

confidence: 99%

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Semirubin. A Novel Dipyrrinone Strapped by Intramolecular Hydrogen Bonds

Huggins

Lightner

2000

J. Org. Chem.

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(4Z)-9-(5-Carboxypentyl)-2,3,7,8-tetramethyl-(10H)-dipyrrin- 1-one (1, semirubin), a new dipyrrinone model for one-half of bilirubin, the yellow-orange neurotoxic pigment of jaundice, was synthesized following Friedel-Crafts acylation of 2,3,7, 8-tetramethyl-(10H)-dipyrrin-1-one (5) with the half-ester acid chloride of adipic acid. Unlike other dipyrrinone models for bilirubin, such as the xanthobilirubic acids, which engage only in intermolecular hydrogen bonding, 1 is unique in having been designed and found to engage in intramolecular hydrogen bonding, between the carboxylic acid and the dipyrrinone lactam and pyrrole. This important conformation-determining structural characteristic, shared by 1 and bilirubin, renders them less polar than their methyl esters and leaves them monomeric in nonpolar solvents, where their esters are dimeric. The corresponding 10-oxo analogue (3) of 1 serves as a model for 10-oxo-bilirubin, a presumed bilirubin metabolite in alternate pathways for bilirubin excretion. Like 1, 3 is found to engage in intramolecular hydrogen bonding. Unlike the methyl ester of 1, the ethyl ester of 3 is not intermolecularly hydrogen bonded in nonpolar solvents.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Semirubin. A Novel Dipyrrinone Strapped by Intramolecular Hydrogen Bonds

Huggins

Lightner

2000

J. Org. Chem.

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“…The following compounds were prepared by established procedures: diethyl 3,3‘-diethyl-4,4‘-dimethyl-2,2‘-dipyrromethane-5,5‘-dicarboxylate ( 1 ), diethyl 2,2‘,4,4‘-tetramethyl-3,3‘-dipyrromethane-5,5‘-dicarboxylate ( 2 ), meso -phenyldipyrromethane ( 4 ), meso -(4-pyridyl)dipyrromethane ( 5 ), bis(3-[( R )-1-(methylheptyloxycarbonyl)-methyl]-2,2‘,4,4‘-tetramethyldipyrromethene) hydrobromide ( 11 ), meso -phenyldipyrromethene ( 14 ), zinc(II) di[bis(3-ethyl-2,2‘,4,4‘-tetramethyldipyrromethene)] ( 18 ), zinc(II) di[bis(3-[( R )-1-(methylheptyloxycarbonyl)-methyl]-2,2‘,4,4‘-tetramethyldipyrromethene)] ( 19 ), zinc(II) dimethyl-( l )tartrate- O , O ‘ -(4-ethyl-2,2‘,5,5‘-tetramethyldipyrromethene-4-propanoate) ( 20 ), zinc(II) di( meso -phenyldipyrromethene) ( 23 ), and N , N ‘ -difluoroboryl-3,3‘,5,5‘-tetramethyldipyrromethene ( 26 ). , …”

Section: Methodsmentioning

confidence: 99%

“…The following compounds were prepared by established procedures: diethyl 3,3′-diethyl-4,4′-dimethyl-2,2′-dipyrromethane-5,5′dicarboxylate (1), 24 diethyl 2,2′,4,4′-tetramethyl-3,3′-dipyrromethane-5,5′-dicarboxylate (2), 25 meso-phenyldipyrromethane (4), 6 meso-(4-pyridyl)dipyrromethane ( 5), 26 23), 30 and N,N′-difluoroboryl-3,3′,5,5′-tetramethyldipyrromethene (26). 31,32 Diethyl 3,3′-Dibromo-4,4′-dimethyl-2,2′-dipyrromethane-5,5′dicarboxylate (3).…”

Section: Methodsmentioning

confidence: 99%

¹⁵N NMR Chemical Shifts for the Identification of Dipyrrolic Structures

et al. 2006

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A variety of dipyrromethanes and dipyrromethenes have been prepared, and their 15N NMR chemical shifts have been measured by two-dimensional correlation to 1H NMR signals. The nitrogen atoms in five examples of dipyrromethanes consistently exhibit chemical shifts around -231 ppm, relative to nitromethane. Seven examples of hydrobromide salts of meso-unsubstituted dipyrromethenes consistently display 15N chemical shifts around -210 ppm, while their corresponding zinc(II) complexes exhibit chemical shifts around -170 ppm. The presence of electron-withdrawing substituents on one of the pyrrolic rings of dipyrromethenes affects the chemical shifts of both of the nitrogen nuclei in the molecule. Boron difluoride complexes of meso-unsubstituted dipyrromethenes display 15N chemical shifts around -190 ppm. Two examples of free-base dipyrromethenes bearing substituents at the meso-position exhibit 15N chemical shifts at approximately -156 ppm, and for the zinc complexes of these compounds at -162 ppm. One-bond nitrogen-hydrogen coupling constants, when measurable, were consistently in the range of -96 Hz. Since the measured 15N chemical shifts have such a high regularity correlated to structure, they can be used as diagnostic indications for identifying the structure of dipyrrolic compounds.

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