182194-87-2Relevant academic research and scientific papers
Copper(I) catalysts for the stereoselective addition of N-chloroamines to double bonds: A diastereoselective radical cyclisation
Heuger, Gerold,Kalsow, Stefanie,Gottlich, Richard
, p. 1848 - 1854 (2007/10/03)
Copper(I) catalysts for the diastereoselective radical cyclisation of N-chloro-N-pentenylamines have been developed. The stereoselectivity of the cyclisation depends upon the ligands employed, proving that the radical is bound to the catalyst during the formation of the new stereocentre and making a catalyst-influenced stereoselective radical reaction possible. The influence of the catalyst on the Beckwith-Houk transition states is discussed. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
Photoreactions of Phenyl-Substituted N-(Pent-4-enyl-1-oxy)pyridine-1(1H)-thiones
Hartung, Jens,Hiller, Margit,Schmidt, Philipp
, p. 1014 - 1023 (2007/10/03)
A series of hitherto unknown N-(pent-4-enyl-1-oxy)pyridine-2(1H)-thiones (6) were prepared from substituted pent-4-enyl tosylates or benzylic chlorides.On irradiation with incandescent light heterocycles 6 liberated alkoxy radicals 2, which were studied for rearrangement reactions.Surprisingly, all transformations involving the 1-phenylpent-4-enyl-1-oxy radical (2a), for example, to give the substituted thioether 8, 2-bromomethyl-5-phenyltetrahydrofuran (11), or the tetrahydrofuran 14a, were not stereoselective.On the other hand 2-, 3-mono-, and 1,5-disubstituted pent-4-enyl-1-oxy radicals 2d-e and 2g cyclized in good yields and with good to excellent stereoselectivities to give the corresponding 2,4-cis- and 2,3-trans-phenyltetrahydrofurfuryl radicals 3d-e, and the trans-2-benzyl-5-methyl substituted intermediate 3g.The major reaction mode of the 4-phenylpent-4-enyl-1-oxy radical (2f) was the 6-endo cyclization, which afforded 3-phenyltetrahydropyran (13f) as the major product (endo:exo=93:7) after trapping with hydrogen donors.According to the experimental data of the present study, the unusual reactivity of the 1-phenylpent-4-enyl-1-oxy radical (2a) in 5-exo-trig ring closures could be caused by a coplanar arrangement of the benzyloxy moiety in the transition state of the cyclization.This interaction would lock the radical center in 2a in a preferred conformation, which would result in similar steric effects for both cis- and trans-cyclizations. - Keywords: alkoxy radicals; cyclizations; pyridinethiones; radicals; tetrahydrofurans
