704-77-8Relevant articles and documents
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Kasiwagi
, p. 985 (1958)
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Metal-Free Transfer Hydrobromination of C-C Triple Bonds
Chen, Weiqiang,Oestreich, Martin
supporting information, p. 4531 - 4534 (2019/06/27)
A transfer hydrobromination of C-C triple bonds inititated by Br?nsted acids is reported. Hydrogen bromide is released stepwise from a bench-stable cyclohexa-1,4-diene-based surrogate, generating biphenyl and ethylene as waste. A range of vinyl bromides was prepared from terminal and internal, mainly acceptor-substituted alkynes with good functional-group tolerance.
Controlling 6-endo-selectivity in oxidation/bromocyclization cascades for synthesis of aplysiapyranoids and other 2,2,6,6-substituted tetrahydropyrans
Brücher, Oliver,Bergstr??er, Uwe,Kelm, Harald,Hartung, Jens,Greb, Marco,Svoboda, Ingrid,Fuess, Hartmut
supporting information; experimental part, p. 6968 - 6980 (2012/09/07)
A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion.
