Oxyanion-Accelerated C<sup>2</sup>−C<sup>6</sup> Cyclization of Benzannulated Enyne-allenes
作者:Steven R. Brunette、Mark A. Lipton
DOI:10.1021/jo991876v
日期:2000.8.1
The cyclization of oxyanion-substituted, benzannulated enyne-allenes was found to proceed rapidly and efficiently at room temperature, producing substituted indanones and fluorenones through a C2-C6 cyclization pathway. These reactions bear close resemblance to thermal C2-C6 cyclizations of enyne-allenes previously reported by Schmittel and others, though the oxyanion-substituted cases cyclize far
Intramolecular Dehydro Diels−Alder Reactions of Diarylacetylenes: Switching between Benzo[<i>b</i>]- and Benzo[<i>c</i>]fluorenones as Products by Controlling the Rearrangement of Cyclic Allene Intermediates
Thermal cyclization of 1-[2-(arylethynyl)phenyl]-3-trimethylsilylpropynones affords a mixture of benzo[b]fluorenones and benzo[c]fluorenones. The ratio of the two isomers can be efficiently varied between 100:0 and 0:100 by introducing substituents with appropriate electronic and steric properties on the aryl rings and using an appropriate solvent.
1- [2-(芳乙炔基)苯基] -3-三甲基甲硅烷基丙炔酮的热环化得到苯并[ b ]芴酮和苯并[ c ]芴酮的混合物。通过在芳基环上引入具有适当电子和空间性质的取代基并使用适当的溶剂,可以有效地在100:0和0:100之间改变两种异构体的比例。
Intramolecular [4 + 2] Cycloaddition Reactions of Diarylacetylenes: Synthesis of Benzo[<i>b</i>]fluorene Derivatives via Cyclic Allenes
intramolecular [4 + 2] cycloaddition to give benzo[b]fluorene derivatives in good yields. The hybridization of the tether connecting the reacting alkynes has a pronounced effect on the course of the reaction. Theoretical calculations and isotopic labeling studies support a mechanism which involves the generation of a cyclic allene intermediate that evolves to the final benzo[b]fluorene.
A comprehensive theoretical and experimental investigation of dehydro Diels-Alder reactions examining the evolution of the cyclic allene intermediates under conditions for intramolecular and ionic and radical intermolecular cycloaromatization processes is reported. Theoretical calculations showed that the most favored intramolecular path for cycloaromatization of 1,2,4-cyclohexatriene 4 and its benzoannulated