119391-50-3Relevant articles and documents
A Radical Version of the Bromo- and the Iodocyclization of Bis(homoallylic) Alcohols - The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring Closures
Hartung, Jens,Kneuer, Rainer,Laug, Stefanie,Schmidt, Philipp,Spehar, Kristina,Svoboda, Ingrid,Fuess, Hartmut
, p. 4033 - 4052 (2007/10/03)
A new synthesis of bromo- and iodomethyl-substituted tetrahydrofurans has been devised. The sequence starts with the conversion of aryl-functionalized bis(homoallylic) alcohols 1 into N-alkenoxythiazole-2(3H)-thiones 6 or pyridine-2(1H)-thiones 7. When photolyzed in the presence of appropriate trapping reagents, thiones 6 and 7 efficiently liberated substituted 4-penten-1-oxyl radicals 2, which underwent synthetically useful 5-exo-trig cyclizations. Cyclized radicals 3 were trapped with BrCCl3 or an adequate iodine atom donor (either n-C4F9I or diethyl 2-iodo-2-methyl malonate) to provide halocyclization products 4 or 5. This strategy has been applied for the synthesis of 3-, 4-, or 5-phenyl-substituted 2-(1-bromo-1-methylethyl)tetrahydrofurans 4a-c (75-90%, 36-96% de), which were not attainable as major products from polar, for example NBS-mediated, bromocyclizations. Aryl-substituted 2-iodomethyl tetrahydrofurans 5 (46-80%) were prepared in a similar way starting from N-alkenoxypyridine-2(1H)-thiones 7 and a suitable iodine atom donor. Diastereomerically pure iodides cis-5 and trans-5 served as starting materials for a stereochemical analysis of disubstituted tetrahydrofurans by NMR spectroscopy and X-ray diffraction analysis. The results of this investigation clarified that all new alkoxyl radical cyclizations followed in terms of regio-and diastereoselectivity the general guidelines which had been established for this type of ring-closure reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Rate Constants for Chalcogen Group Transfers in Bimolecular Substitution Reactions with Primary Alkyl Radicals
Curran, Dennis P.,Martin-Esker, Amanda A.,Ko, Sung-Bo,Newcomb, Martin
, p. 4691 - 4695 (2007/10/02)
Rate constants for group transfers of the MeS, PhS, PhSe, and PhTe groups from chalcogen-substituted acetate, acetonitrile, malonate, and malononitrile compounds, from N-(phenylthio)phthalimide and from Me2S2 and Ph2S2 to primary alkyl radicals, have been determined by competition kinetics using PTOC esters as the radical precursors and competing trapping agents.Thio group transfers from malononitrile derivatives are marginally faster than the corresponding group transfer from the symmetrical disulfide, and the rate constant for PhSe group transfer from PhSeSePh isgreater than those from the derivatives studied here.Substituent effects suggest that the chalcogen transfer reactions may be concerted.For three cases in which direct comparisons can be made, the rate constants for reactions of phenylchalcogenides are approximately equal to those for halogen atom transfer when the chalcogen and halide are in the same row of the periodic table and the radical resulting from displacement is the same.The rate constants reported in this work will be useful for the rational design of synthetic schemes based on homolytic group transfer chemistry.
Rate Constants for Halogen Atom Transfer from Representative α-Halocarbonyl Compounds to Primary Alkyl Radicals
Curran, Dennis P.,Bosch, Eric,Kaplan, Jere,Newcomb, Martin
, p. 1826 - 1831 (2007/10/02)
Rate constants for halogen atom transfer from diethyl methyliodomalonate (7a), iodoacetonitrile (7b), ethyl 2-methyl-2-iodopropanoate (7c), ethyl iodoacetate (7d), diethyl methylbromomalonate (7e), and ethyl bromoacetate (7f) to simple primary alkyl radicals have been studied by a variety of competition reactions.The Arrhenius functions for halogen atom transfer to the undecyl radical from halides 7d and 7f are log (kI, M-1 s-1) = 10.4 - 4.4/θ and log (kBr, M-1 s-1) = 10.4 - 8.2/θ, respectively.The rate constants for halogen atom transfer to a primaryradical from the series of compounds 7a-7f at 50 deg C are 1.8 x 109, 1.7 x 109, ca. 6 x 108, 2.6 x 107, 1.0 x 106, and 7.0 x 104 M-1 s-1, respectively.The kinetic values are useful for the planning of synthetic methods that incorporate an atom transfer-cyclization process.
