19547-01-4Relevant articles and documents
Highly reactive porphyrin-iron-oxo derivatives produced by photolyses ofmetastable porphyrin-iron(IV) diperchlorates
Pan, Zhengzheng,Wang, Qin,Sheng, Xin,Horner, John H.,Newcomb, Martin
experimental part, p. 2621 - 2628 (2009/09/07)
Photolyses of metastable porphyrin-iron(IV) diperchlorates in laser flash photolysis reactions gave highly reactive transients. The systems studied were 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetramesitylporphyrin (TMP), and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP). The new species, which decayed within milliseconds in acetonitrile solutions, were shown to react with organic substrates by oxo-transfer reactions involving insertions into carbon-carbon double bonds of alkenes and styrenes or benzylic carbon-hydrogen bonds of arenes. The order of reactivity was OEP > TPP > TMP. Second-order rate constants for reactions with several substrates at 22 °C were determined; representative values of rate constants for the TPP derivative were k = 8.6 × 105 M-1 s-1 for styrene, k = 2.5 × 106 M-1 s-1 for cyclohexene, and k = 7.7 × 104M-1 s-1 for ethylbenzene. These porphyrin-iron-oxo transients reacted 4-5 orders of magnitude faster than the corresponding iron(IV)-oxo porphyrin radical cations with rate constants similar to those of porphyrin-manganese(V)-oxo derivatives. Rate constants for oxidations of benzylic C-H positions of arenes correlated with the C-H bond dissociation energies, and Hammett correlations for reactionswith substituted styrenes had p+ values ranging from-0.5 to- 0.7, reflecting electrophilic character of the oxidants and their high reactivity. On the basis of their unique UV-visible spectra, high reactivities, and oxo-transfer properties, the new transients are tentatively identified as porphyrin-iron(V)-oxo perchlorates, electronic isomers (or valence tautomers) of well-known iron(IV)-oxo porphyrin radical cations.
Toward the creation of NMR databases in chiral solvents for assignments of relative and absolute stereochemistry: proof of concept.
Kobayashi,Hayashi,Tan,Kishi
, p. 2245 - 2248 (2007/10/03)
[structure: see text] An NMR database approach in a chiral solvent allows us to predict both relative and absolute stereochemistry of an unknown compound without degradation and/or derivatization. N,alpha-Dimethylbenzylamine (DMBA) is a suitable solvent for this purpose. Using the C.5-C.10 portion of oasomycin A, the feasibility and reliability of this approach is demonstrated.
PREPARATION OF DEUTERIATED 1-PHENYLETHANOLS BY REDUCTIVE DEHALOGENATION OF THE CORRESPONDING HALOGENOACETOPHENONES WITH RANEY ALLOYS IN AN ALKALINE DEUTERIUM OXIDE SOLUTION
Tashiro, Masashi,Mataka, Shuntaro,Nakamura, Hiroshi,Nakayama, Kouji
, p. 179 - 182 (2007/10/02)
Deuteriated 1-phenylethanols were prepared by reductive dehalogenation of the corresponding halogenoacetophenones with Raney Ni-Al and Cu-Al alloys in 5percent NaOD-D2O solution.It was found that the Ni-Al alloy introduced greater than expected numbers of deuterium atoms in the phenyl ring, but the expected deuteriated 1-phenylethanols were obtained in high yield and in high isotopic purity when Raney Cu-Al alloy was used.
