Formal radical closure onto aromatic rings—a general route to carbocycles
作者:Derrick L. J. Clive、Rajesh Sunasee、Zhenhua Chen
DOI:10.1039/b803308k
日期:——
A general method is described for indirectly effecting radical carbocyclization of an alkyl chain onto an aromatic ring. Birch reductive-alkylation of aromatic tert-butyl esters with α,Ï-dibromides, chromium(VI)-mediated oxidation of the resulting 1,4-dienes and Finkelstein displacement of Brâ with NaI gives cross-conjugated ketones that undergo radical cyclization. The products are easily aromatized to phenols by silylation, Saegusa oxidation and treatment with BiCl3.H2O. A special feature of the route is that it allows attachment of a substituent to the original aromatic ring in place of the phenolic oxygen of the normal product.
[Ir(cod)Cl](2)/DPPE was found to be a new catalyst for the cycloaddition of alpha,omega-diynes with monoynes to give polysubstituted benzene derivatives in high yields. Internal monoynes as well as terminal monoynes could be used. The reaction tolerates a broad range of functional groups such as alcohol, amine, alkene, ether, halogen, and nitrile. The reaction of 1,6-octadiyne derivatives with 1-alkynes gives ortho products and meta products. The regioselectivity could be controlled by the choice of ligand. The reaction with DPPE was meta selective, with meta selectivity of up to 82%. The reaction with DPPF was ortho selective, with ortho selectivity of up to 88%. We propose a mechanism to account for this regioselective cycloaddition. [Ir(cod)Cl-2]2/DPPE also catalyzed the cycloaddition of alpha-omega-diynes with 2,5-dihydrofuran to give bicyclic cyclohexadiene derivatives. The reaction with 2,3-dihydrofuran and n-butyl vinyl ether gave benzene derivatives instead of cyclohexadiene derivatives. We also propose a mechanism to account for this novel aromatization that includes cleavage of the C-O bond.
Grigg, Ronald; Scott, Ronald; Stevenson, Paul, Journal of the Chemical Society. Perkin transactions I, 1988, p. 1357 - 1364
作者:Grigg, Ronald、Scott, Ronald、Stevenson, Paul
DOI:——
日期:——
ADAMCZYK, M.;WATT, D. S.;NETZEL, D. A., J. ORG. CHEM., 1984, 49, N 22, 4226-4237
作者:ADAMCZYK, M.、WATT, D. S.、NETZEL, D. A.
DOI:——
日期:——
Synthesis of biological markers in fossil fuels. 2. Synthesis and carbon-13 NMR studies of substituted indans and tetralins