3658-79-5Relevant articles and documents
Porphyrin arrays responsive to additives. Fluorescence tuning
Yamamura, Takeshi,Suzuki, Shingo,Taguchi, Tomotaka,Onoda, Akira,Kamachi, Toshiaki,Okura, Ichiro
, p. 11719 - 11726 (2009)
The application of low-flux sunlight begins with the synthesis of effective antenna systems. This requires the development of dye integrates with optimized dye orientation for effective energy transfer. We here report a series of peptide-linked porphyrin arrays, denoted by Boc-(PorZn,S) n-OBut (n = 2, 4, and 8), that change their dye orientation to increase fluorescence responsively to additive reagents. The B-band absorption (AB) regions of the arrays show blue shifts (dimer, 407.6 nm; tetramer, 408.2 nm; octamer, 407.8 nm) in organic solvents as compared to that of Boc-PorZn,S-OBut (monomer, 422.6 nm) and the fluorescence yield Φ? of the arrays decreases with increasing n, obeying the relationship Φ? = 0.03/n1.5.; however, the arrays are tuned up in fluorescence emission by the addition of 1,2-diaminoethane (en). The addition of a sufficient amount of en increases the fluorescence of the porphyrins in monomer, dimer, tetramer, and octamer by ～5, ～12, ～12, and >730 times, respectively, when compared with that observed in the absence of en. This also causes asymptotic red shifts in absorption (AB) bands (B-band λmax: 410 to 429-430 nm), as well as changes in circular dichroism (CD) spectra, and makes porphyrins approach new mutual asymmetric orientations. Our results show the potentiality of the tunable dye polymers that are a posteriori optimized in dye orientation and fluorescence emission by additive reagents for the development of effective light-harvesting materials.
Hexameric resorcinarene capsule is a bronsted acid: Investigation and application to synthesis and catalysis
Zhang, Qi,Tiefenbacher, Konrad
supporting information, p. 16213 - 16219 (2013/11/19)
Molecular capsules have attracted interest as simple enzyme mimetics and several examples of catalytic transformations in water-soluble metal-ligand based systems have been reported. This is not the case for hydrogen-bond based molecular capsules, which in contrast can be employed in organic solvents. We describe herein our investigations of such a system: The resorcin[4]arene hexamer is one of the largest hydrogen bond-based self-assembled capsules and has been studied intensively due to its ready availability. We present evidence that the capsule acts as a reasonably strong Bronsted acid (pK a approximately 5.5-6). This finding explains the capsule's high affinity toward tertiary amines that are protonated and therefore encounter cation-π interactions inside the cavity. We were able to translate this finding into a first synthetic application: A highly substrate-selective Wittig reaction. We also report that this property renders the capsule an efficient enzyme-like catalyst for substrate selective diethyl acetal hydrolysis.
Method for producing enol ethers
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, (2008/06/13)
Enol ethers of the formula I where R1is an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radical which may carry further substituents which do not react with acetylenes or allenes, and the radicals R, independently of one another, are hydrogen or aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radicals, which may be bonded to one another to form a ring, and m is 0 or 1, are prepared by reacting an acetal or ketal of the formula II with an acetylene or allene of the formula III or IV where R and R1have the abovementioned meanings, in the gas phase at elevated temperatures in the presence of a zinc- or cadmium- and silicon- and oxygen-containing heterogeneous catalyst.
1H and 13C NMR Spectra of 2-Halo-2-alkenals and Their Acetals
Rulev, A. Yu.,Mokov, A. S.,Krivdin, L. B.,Keiko, N. A.,Voronkov, M. G.
, p. 1465 - 1469 (2007/10/03)
The electronic structure of a series of 2-halo-2-alkenals R2(R1)C=CXCHO and their acetals R2(R1)C=CXCH(OR3)2 is studied by 1H and 13C NMR spectroscopy.In the molecules of 2-fluoro-2-alkenals the electron density of the double bond is shifted toward the β-carbon atom.In contrast, in isostructural 2-chloro- and 2-bromo-2-alkenals the most probable centers of a nucleophilic attack are the β-carbon atom of the double bond and the carbonyl carbon atom.Owing to the lower acceptor power of the acetal group as compared to the aldehyde group, the reactivity of the double bond in acetals is decreased, and the direction of its polarization is the same as in haloalkenes.
Potassium on Alumina as a Reagent for Reductive Decyanation of Alkylnitriles.
Savoia, Diego,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
, p. 3227 - 3229 (2007/10/02)
Highly dispersed potassium over neutral alumina (K/Al2O3), easily prepared by melting potassium over alumina in an inert atmosphere, is capable of effecting reductive cleavage of the cyano group in alkylnitriles in hexane at room temperature in 70-91percent yield.This decyanation method is applied in the key step of a novel synthesis of (Z)-9-dodecen-1-yl acetate, the sex pheromone of Paralobesia viteana.
