3750-36-5Relevant articles and documents
Size-Selective Hydroformylation by a Rhodium Catalyst Confined in a Supramolecular Cage
Nurttila, Sandra S.,Brenner, Wolfgang,Mosquera, Jesús,van Vliet, Kaj M.,Nitschke, Jonathan R.,Reek, Joost N. H.
, p. 609 - 620 (2019/01/04)
Size-selective hydroformylation of terminal alkenes was attained upon embedding a rhodium bisphosphine complex in a supramolecular metal–organic cage that was formed by subcomponent self-assembly. The catalyst was bound in the cage by a ligand-template approach, in which pyridyl–zinc(II) porphyrin interactions led to high association constants (>105 m?1) for the binding of the ligands and the corresponding rhodium complex. DFT calculations confirm that the second coordination sphere forces the encapsulated active species to adopt the ee coordination geometry (i.e., both phosphine ligands in equatorial positions), in line with in situ high-pressure IR studies of the host–guest complex. The window aperture of the cage decreases slightly upon binding the catalyst. As a result, the diffusion of larger substrates into the cage is slower compared to that of smaller substrates. Consequently, the encapsulated rhodium catalyst displays substrate selectivity, converting smaller substrates faster to the corresponding aldehydes. This selectivity bears a resemblance to an effect observed in nature, where enzymes are able to discriminate between substrates based on shape and size by embedding the active site deep inside the hydrophobic pocket of a bulky protein structure.
Synthesis and properties of mesobilirubins XIIγ and XIIIγ and their mesobiliverdins
Sabido, Portia Mahal G.,Lightner, David A.
, p. 775 - 789 (2014/05/20)
The title pigments, with propionic acid groups displaced to the lactam end rings, were synthesized for the first time by the "1 + 2 + 1" approach, coupling two equivalents of a monopyrrole to a dipyrrylmethane (to give XIIγ), or the "2 + 2" approach, self-coupling two equivalents of a dipyrrinone (to give XIIIγ). Using the "1 + 2 + 1" approach, mesobilirubin IIIα was also prepared. Mesobilirubins XIIγ and XIIIγ are more polar than mesobilirubin IIIα and unlike IIIα cannot effectively engage the propionic acid groups in intramolecular hydrogen bonding to the dipyrrinone components. The new mesobilirubins give exciton coupled circular dichroism spectra in the presence of human serum albumin or quinine, with the XIIγ isomer exhibiting Cotton effect intensities nearly as strong as those from the IIIα isomer; whereas, the XIIIγ isomer exhibits far weaker intensities. Mesobilirubin IIIα requires glucuronidation for hepatobiliary elimination; whereas, XIIγ and XIIIγ do not, and they are excreted intact across the liver into bile. The corresponding biliverdins XIIγ and XIIIγ are reduced only slowly by biliverdin IXα reductase, in contrast to the fast reduction of the natural IXα isomer. Graphical abstract: [Figure not available: see fulltext.]
Fluorinated photosensitizers: Synthesis, photophysical, electrochemical, intracellular localization, in vitro photosensitizing efficacy and determination of tumor-uptake by 19F in vivo NMR spectroscopy
Pandey, Suresh K.,Gryshuk, Amy L.,Graham, Andrew,Ohkubo, Kei,Fukuzumi, Shunichi,Dobhal, Mahabeer P.,Zheng, Gang,Ou, Zhongping,Zhan, Riqiang,Kadish, Karl M.,Oseroff, Allan,Ramaprasad,Pandey, Ravindra K.
, p. 10059 - 10073 (2007/10/03)
For in vivo NMR studies, starting from pyrroles, a series of fluorinated porphyrins were synthesized by following the MacDonald reaction conditions. Upon reaction with osmium tetroxide, a fluorinated porphyrin containing four trifluoromethyl groups (12 fl
Oxidation with Perhalogenated, Water-soluble Metalloporphyrins: Application to Oxidation of Substituted 2-Methylpyrroles
Karunaratne, Veranja,Dolphin, David
, p. 2105 - 2106 (2007/10/02)
Perchlorinated, sulfonated metalloporphyrin 1 cleanly oxidized substituted 2-methylpyrroles 2a-f in the presence of iodosylbenzene to produce the corresponding allylic alcohols 3a-f.
SYNTHESIS OF RIGIDLY LINKED TRIAD MOLECULES BASED ON OCTAALKYLPORPHYRIN, CAPABLE OF MULTISTEP ELECTRON TRANSFER
Gribkov, A.A.,Borovkov, V.V.,Evstigneeva, R.P.,Sakata, Y.
, p. 905 - 915 (2007/10/02)
We have designed and carried out the synthesis of triad model systems containing octaalkylporphyrin, benzoquinone, and trichlorobenzoquinone with an oxidation-reduction potential gradient in the molecule.The quinone moieties are fixed relative to the porphyrin using spirononane and methylene spacers.
Electron transfer in bis-porphyrin donor-acceptor compounds with polyphenylene spacers shows a weak distance dependence
Helms, Anna,Heiler, David,McLendon, George
, p. 6227 - 6238 (2007/10/02)
A series of phenylene-bridged bis-porphyrin adducts have been synthesized, containing one, two, or three phenyl bridges. Complete synthetic details are provided. For studies of photochemical electron transfer, mixed metals wre incorporated, with zinc in one porphyrin macrocycle and FeIII (bis-imidazole) in the other macrocycle. When photoexcited, an electron is transferred from Zn to FeIII. The rate of this process drops only slowly with distance: kα exp(βr), with β = 0.4 A?-1. This dependence can be predicted by a simple theory which assumes that the drop does not reflect increased distance, but rather reflects the break in conjugation which occurs at each phenyl juncture due to the biphenyl twist angle of ca. 50°. Inefficient overlap in this angle results in a rate drop of ca. 6-fold per phenyl ring, in good agreement with the observed results.
Porphyrins with Exocyclic Rings. 2. Synthesis of Geochemically Significant Tetrahydrobenzoporphyrins from 4,5,6,7-Tetrahydro-2H-isoindoles
May, Donald A.,Lash, Timothy D.
, p. 4820 - 4828 (2007/10/02)
Benzo- and tetrahydrobenzoporphyrins are widespread constituents of oil shales and petroleum.Although the origins of these materials are not known, a case is made for divinylchlorophyll a, a widespread pigment in marine algae, being the precursor to many of these geoporphyrins.Total syntheses of four tetrahydrobenzoporphyrins related to etioporphyrin III are described.Tetrahydroisoindoles were prepared by condensation of isocyanoacetates with 1-nitrocyclohexene in the presence of DBU or by reaction of aminomalonates with 2-formylcyclohexanone.Condensation of 3-unsubstituted 4,5,6,7-tetrahydro-2H-isoindoles 23c and 23d with (acetoxymethyl)pyrroles in the presence of Montmorillonite clay gave dipyrrylmethanes 28a and 36a in excellent yield.Hydrogenolysis of the benzyl esters and subsequent acid-catalyzed condensation with pyrrole aldehydes 37a and /or 37b gave a series of a,c-biladiene dihydrobromides.Copper(II) mediated cyclization of the a,c-biladienes 32, 33, 35, and 38, followed by demetallation with 15percent sulfuric acid-trifluoroacetic acid, gave four isomeric tetrahydrobenzoporphyrins 10-13 in unusually high yield.This work provides a general route for the synthesis of these important porphyrin molecular fossils.
THE TOTAL SYNTHESIS OF BILIVERDINS OF BIOLOGICAL INTEREST
Awruch, Josefina,Frydman, Benjamin
, p. 4137 - 4146 (2007/10/02)
The total synthesis of eight biliverdin isomers was achieved by oxidation of the corresponding 1,19-di-t-butyloxycarbonyl-b-bilenes.One of the biliverdin isomers is mesobiliverdin IXα - a dipropionate bilitriene -, one is a diacetate bilitriene, three iso
