Synthesis of Cyclic Enol Ethers from Alkenyl-β-dicarbonyl Compounds
作者:Helena M. C. Ferraz、Myrian K. Sano、Marta R. S. Nunes、Graziela G. Bianco
DOI:10.1021/jo011089+
日期:2002.6.1
the cyclofunctionalization of eleven differently substituted alkenyl-beta-dicarbonyl compounds, employing three electrophilic reagents, namely, iodine, p-methoxyphenyltellurium trichloride, and phenylselenenyl bromide. The reactions occur through the enolic form of the substrates, to afford the corresponding iodo-, telluro-, or selenocyclic enolethers. Substrates bearing trisubstituted double bonds
Iodo- and bromo-enolcyclization of 2-(2-propenyl)cyclohexanediones and 2-(2-propenyl)cyclohexenone derivatives using iodine in methanol and pyridinium hydrobromide perbromide in dichloromethane
作者:Malose J. Mphahlele、Thwanthwadi B. Moekwa
DOI:10.1039/b505491e
日期:——
α-Allylcyclohexane-1,3-diones undergo one-pot iodine–methanol promoted iodocyclization and oxidative aromatization to afford variously substituted 2-iodomethyltetrahydrobenzofuran-4-ones (minor) and 2-iodomethyl-4-methoxydihydrobenzofuran derivatives (major). On the other hand, the α-allyl-1,3-cyclohexanediones react with pyridinium hydrobromide perbromide in dichloromethane to afford mixtures of 2-bromomethyltetrahydrobenzofuran-4-ones (major) and 3-bromomethyltetrahydrobenzopyran-5-ones (minor). The prepared products and their derivatives were characterized using a combination of NMR, FT-IR and mass spectroscopic techniques.
The first non-phosphane iridium catalyst, made from [IrCl(cod)}(2)] and iPr-pybox (shown schematically; cod=1,5-cyclooctadiene), for allylic alkylation in neutral medium was discovered by a simple, rapid, and inexpensive screening assay. The red coloration upon treatment of the reaction mixtures with Fast Red (see the 96-well plate) indicates the presence of 1-naphthol and thus the occurrence of allylic alkylation.
Mahajan, Jaswant Rai; Monteiro, Maria Beatriz, Journal of Chemical Research, Miniprint, 1980, # 8, p. 3278 - 3293