34825-93-9Relevant articles and documents
Ammonium-directed olefinic epoxidation: Kinetic and mechanistic insights
Brennan, Meabh B.,Claridge, Timothy D.W.,Compton, Richard G.,Davies, Stephen G.,Fletcher, Ai M.,Henstridge, Martin C.,Hewings, David S.,Kurosawa, Wataru,Lee, James A.,Roberts, Paul M.,Schoonen, Anne K.,Thomson, James E.
, p. 7241 - 7261 (2012/11/07)
The ammonium-directed olefinic epoxidations of a range of differentially N-substituted cyclic allylic and homoallylic amines (derived from cyclopentene, cyclohexene, and cycloheptene) have been investigated, and the reaction kinetics have been analyzed. The results of these studies suggest that both the ring size and the identity of the substituents on nitrogen are important in determining both the overall rate and the stereochemical outcome of the epoxidation reaction. In general, secondary amines or tertiary amines with nonsterically demanding substituents on nitrogen are superior to tertiary amines with sterically demanding substituents on nitrogen in their ability to promote the oxidation reaction. Furthermore, in all cases examined, the ability of the (in situ formed) ammonium substituent to direct the stereochemical course of the epoxidation reaction is either comparable or superior to that of the analogous hydroxyl substituent. Much slower rates of ring-opening of the intermediate epoxides are observed in cyclopentene-derived and cycloheptene-derived allylic amines as compared with their cyclohexene-derived allylic and homoallylic amine counterparts, allowing for isolation of these intermediates in both of the former cases.
Ammonium-directed oxidation of cyclic allylic and homoallylic amines
Bond, Christopher W.,Cresswell, Alexander J.,Davies, Stephen G.,Fletcher, Ai M.,Kurosawa, Wataru,Lee, James A.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Thomson, James E.
supporting information; experimental part, p. 6735 - 6748 (2009/12/31)
(Chemical Equation Presented) The ammonium-directed olefinic oxidation of a range of cyclic allylic and homoallylic amines has been investigated. Functionalization of a range of allylic 3-(N,N-dibenzylamino)cycloalk-1-enes with m-CPBA in the presence of Cl3CCO2H gives exclusively the corresponding syn-epoxide for the 5-membered ring (>99:1 dr), the anti-epoxide for the 8-membered ring (>99:1 dr), and predominantly the anti-epoxide for the 7-membered ring (94:6 dr). Oxidation of the homoallylic amines 3-(Nbenzylamino) methylcyclohex-1-ene and 3-(N,N-dibenzylamino)methylcyclohex-1-ene gave, in both cases, the correspondingN-protected 1,2-anti-2,3-syn-3-aminomethylcyclohexane- 1,2-diol with high levels of diastereoselectivity (g90:10 dr). The versatile synthetic intermediates resulting from these oxidation reactions are readily transformed into a range of amino diols.
A new mechanism for reactions of carbenes and bicyclo[1.1.0]butanes
Xu,Miebach,Brinker,Smith
, p. 4461 - 4464 (2007/10/02)
Reactions of tricyclo[4.1.0.02,7]heptane (1) with dihalocarbenes and bromine are reported. A new side bond opening mechanism for reactions of carbenes and bicyclo[1.1.0]butanes is proposed.
Cycloalkylmethyl Radicals. Part 4. Electron Spin Resonance Study of Conformational Equilibria in Cyclohexenylmethyl and 4-Alkylcyclohexenylmethyl Radicals
Walton, John C.
, p. 1641 - 1646 (2007/10/02)
For cyclohex-2-enylmethyl and 4-alkoxycyclohex-2-enylmethyl radicals the quasi-axial and the quasi-equatorial conformers can both be observed by e.s.r. spectroscopy.Similary, the axial and equatorial conformers of cyclohex-3-enylmethyl radical can be distinguished by e.s.r. spectroscopy.The conformational free-energy difference of the CH2. group in the 2-position, -ΔGdeg300, was found to be 0.17 +/- 0.03 kcal mol-1 and in the 3-position -ΔGdeg300=0.0 +/- 0.1 kcal mol-1.The Arrhenius parameters for inversion of the half-chair conformation of cyclohex-2-enylmethyl radical were determined by lineshape analysis of the exchange-broadened spectra and found to be: log(kf/s-1)=12.3 - (5.7 kcal mol-1)/2.3RT and log(kb/s-1)=12.0 - (5.5 kcal mol-1)/2.3RT.The barrier to rotation about the C.α-Cβ bond in a cyclohexenylmethyl radicals is much less than the barrier in a cyclohexylmethyl radical because the former radical has only one syn-axial hydrogen on C(5) to impede the rotation whereas the latter radical has two syn-axial hydrogens on C(3) and C(5).
Homolytic Ring Fission reactions of Bicycloalkanes and Bicycloalk-2-yl Radicals: Electron Spin Resonance Study of Cycloalkenylmethyl Radicals
Roberts, Charles,Walton, John C.
, p. 879 - 886 (2007/10/02)
Hydrogen abstraction from bicycloalkanes (n=3-6) by t-butoxyl radicals was examined by an e.s.r. technique.The main site of attack was C(2) giving bicycloalk-2-yl radicals which rearranged by β-scission of the outer cyclopropane bonds to give cycloalkenylmethyl radicals.This is in contrast to the bicycloalk-2-yl radicals (n=1,2) which rearranged by fission of the inter-ring bonds to give cycloalkenyl radicals. β-Scission in bicycloalk-2-yl radicals was examined by semi-empirical SCF MO calculations.The conformations and barriers to internal rotation of the cycloalkenylmethyl radicals were determined from the variation in the β-H hyperfine splitting constants with temperature.Photobromination of bicycloalkanes (n=3,4) was also investigated in CCl4 solution.The main process was bimolecular homolytic substitution (SH2) by bromine atoms at the cyclopropane carbons, but there was an increase in hydrogen abstraction with ring size.The SH2 reactions parallel the β-scission reactions of the bicycloalk-2-yl radicals in that the main bond undergoing fission changes from the inter-ring bond to the outer cyclopropane bond as the ring size increases.
SYNTHESIS OF β-(2,3-EPOXYCYCLOHEXYL)ALANINE AND ALANYL-β-(2,3-EPOXYCYCLOHEXYL)ALANINE
Smulkowski, Maciej,Dzieduszycka, Maria,Borowski, Edward
, p. 699 - 704 (2007/10/02)
Syntheses of new analog of antibiotic tetaine alanyl-β-(2,3-epoxycyclohexyl)alanine and its C-terminal amino acid are described.
Synthetic Applications of Metal Halides.Conversion of Cyclopropylmethanols into Homoallylic Halides.
McCormick, J.P.,Barton, Donald L.
, p. 2566 - 2570 (2007/10/02)
Magnesium and beryllium halides in refluxing diethyl ether effect the transformation of cyclopropylmethanols into homoallylic halides,in contrast to several other metal halides and Lewis acid/nucleophile combinations which were examined.Magnesium bromide and iodide are particularly effective: conditions are mild,yields are high,and little or no byproducts are formed.Tertiary and benzylic alcohols are more reactive than secondary alcohols,while the latter are converted into E homoallylic halides with high stereoselectivity.Cyclopropylmethanol itself fails to react.In the cases of magnesium halide reactions with bicyclo-2-hexanol and bicyclo-2-heptanol,addition of an equimolar amount of zinc halide not only caused substantial rate enhancement but also increased regioselectivity.
