A convergent route to dihydrobenzofuran neolignans via a formal 1,3-cycloaddition to oxidized phenols
摘要:
Oxidation of p-methoxy-substituted phenols with iodobenzene bis-trifluoroacetate in the presence of electron-rich styrene derivatives affords trans-dihydrobenzofurans stereoselectively.
Mechanistic aspects and synthetic applications of the electrochemical and iodobenzene bistrifluoroacetate oxidative 1,3-cycloadditions of phenols and electron-rich styrene derivatives
摘要:
Anodic oxidation of p-methoxy-substituted phenols and electron-rich styrene or propenylbenzene derivatives affords in good yield trans-dihydrobenzofurans derived from a formal 1,3-oxidative cycloaddition of the phenol to the styrene derivative. The yield of product in this electrochemical oxidation depends upon the ratio of phenol to styrene derivative, current density, and to a lesser extent the amount of supporting electrolyte. While p-methoxyphenol and 4-methoxy-3-methylphenol give good yields of the dihydrobenzofurans using 1:1 molar ratio of reactants, 3,4-dimethoxyphenol requires a 3-4 molar excess of the styrene derivative for a comparable yield of product. Although 4-methoxy-1-naphthol shows yields comparable to p-methoxyphenol in the anodic cycloaddition reaction, 1- and 2-naphthol gave very low yields of product. Qualitatively, trans- and cis-1,2-dimethoxy-4-propenylbenzene show similar yields in the cycloaddition reaction. Many of these same substrates were examined using iodobenzene bis(trifluoroacetate) as oxidant, and the same products were formed as in the electrochemical oxidations noted above. However, for the reaction of 2-naphthol and 1,2-dimethoxy-4-propenylbenzene the iodobenzene bis(trifluoroacetate) oxidation gave a much better yield of the product. A mechanism involving reaction of a phenoxy radical-styrene radical cation pair is considered and discussed.
A convergent route to dihydrobenzofuran neolignans via a formal 1,3-cycloaddition to oxidized phenols
作者:Shaopeng Wang、Bradley D. Gates、John S. Swenton
DOI:10.1021/jo00006a003
日期:1991.3
Oxidation of p-methoxy-substituted phenols with iodobenzene bis-trifluoroacetate in the presence of electron-rich styrene derivatives affords trans-dihydrobenzofurans stereoselectively.
WANG, SHAOPENG;GATES, BRADLEY D.;SWENTON, JOHN S., J. ORG. CHEM. , 56,(1991) N, C. 1979-1981
作者:WANG, SHAOPENG、GATES, BRADLEY D.、SWENTON, JOHN S.
DOI:——
日期:——
Mechanistic aspects and synthetic applications of the electrochemical and iodobenzene bistrifluoroacetate oxidative 1,3-cycloadditions of phenols and electron-rich styrene derivatives
作者:Bradley D. Gates、Peter Dalidowicz、Andrew Tebben、Shaopeng Wang、John S. Swenton
DOI:10.1021/jo00033a040
日期:1992.3
Anodic oxidation of p-methoxy-substituted phenols and electron-rich styrene or propenylbenzene derivatives affords in good yield trans-dihydrobenzofurans derived from a formal 1,3-oxidative cycloaddition of the phenol to the styrene derivative. The yield of product in this electrochemical oxidation depends upon the ratio of phenol to styrene derivative, current density, and to a lesser extent the amount of supporting electrolyte. While p-methoxyphenol and 4-methoxy-3-methylphenol give good yields of the dihydrobenzofurans using 1:1 molar ratio of reactants, 3,4-dimethoxyphenol requires a 3-4 molar excess of the styrene derivative for a comparable yield of product. Although 4-methoxy-1-naphthol shows yields comparable to p-methoxyphenol in the anodic cycloaddition reaction, 1- and 2-naphthol gave very low yields of product. Qualitatively, trans- and cis-1,2-dimethoxy-4-propenylbenzene show similar yields in the cycloaddition reaction. Many of these same substrates were examined using iodobenzene bis(trifluoroacetate) as oxidant, and the same products were formed as in the electrochemical oxidations noted above. However, for the reaction of 2-naphthol and 1,2-dimethoxy-4-propenylbenzene the iodobenzene bis(trifluoroacetate) oxidation gave a much better yield of the product. A mechanism involving reaction of a phenoxy radical-styrene radical cation pair is considered and discussed.