- Syntheses of per-15N labeled etioporphyrins I-IV and a related tetrahydrobenzoporphyrin for applications in organic geochemistry and vibrational spectroscopy
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Nitrogen-15 labeled pyrroles have been prepared from commercially available 15N glycine or sodium nitrite using the Barton-Zard, Knorr, and Kleinspehn approaches. These pyrroles were used as intermediates in the synthesis of per-15N labeled porphyrins needed for the analysis and assignment of vibrational spectra for sedimentary porphyrins. Etioporphyrin-I was prepared via pyrromethene intermediates, while etioporphyrins II-V and a related tetrahydrobenzoporphyrin were synthesized via stepwise routes involving the copper(II) mediated cyclization of a,c-biladienes as the key step. Detailed analyses of both the proton and carbon-13 NMR spectra provide nitrogen-15 coupling constants for these important structures.
- Lash, Timothy D.,Chen, Shaohua
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p. 11577 - 11600
(2007/10/03)
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- Porphyrins with exocyclic rings. Part 10.1 Synthesis of meso,β- propanoporphyrins from 4,5,6,7-tetrahydro-1H-indoles
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Benzyl (6) and tert-buty1 3-methyl-4,5,6,7-tetrahydro-1H-indole-2- carboxylates (28) were easily prepared from cyclohexanone using a variation of the Knorr pyrrole condensation. Regioselective oxidation with lead tetraacetate gave the corresponding 7-acetoxy derivatives, or related solvolysis products, and subsequent reaction with 5-unsubstituted pyrrole-2- carboxylates in the presence of p-toluenesulfonic acid in acetic acid gave a series of 7-pyrrolyltetrahydroindoles 16 in excellent overall yields. Cleavage of the protective ester units, followed by acid-catalyzed condensation with diformyldipyrrylmethanes 19 under modified MacDonald '2 + 2' conditions gave good yields of meso,β-propanoporphyrins 26. This chemistry was sufficiently versatile that a porphyrin with two six-membered exocyclic rings (34) could be prepared by the same methodology. On the other hand, attempts to cyclize an a,c-biladiene 37 incorporating a six-membered carbocyclic ring gave moderate to poor yields of the required meso,β- propanoporphyrin 26a, probably due to a deleterious steric interaction between the carbocyclic ring and an adjacent alkyl substituent. Nonetheless, the results described below demonstrate the value of this approach for the synthesis of sedimentary cycloalkanoporphyrins.
- Lash, Timothy D.
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p. 359 - 374
(2007/10/03)
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- Thermochemistry of Solution of Linear Pyrroles
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The enthalpies of solution of a series of symmetrically substituted linear pyrroles in benzene, tetrachloromethane, chloroform, dimethylformamide, and pyridine were measured calorimetrically at 298 K.The effect of substituents in pyrrole molecules on the energy characteristics of their solvation by organic solvents is discussed.
- Berezin, M. B.,Semeikin, A. S.,V'yugin, A. I.
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p. 1265 - 1268
(2007/10/03)
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