Studies on Intramolecular Higher-Order Cycloaddition Reactions
摘要:
Thermal, metal-free, and metal-promoted intramolecular higher-order cycloadditions are described. Substrates in which the tropone (2,4,6-cycloheptatrien-1-one) nucleus is tethered to various diene moieties undergo exo-selective [6 pi + 4 pi] cycloaddition under thermal conditions to afford stereochemically defined tricyclic products. The substrates employed in this study were prepared by addition of the Grignard derivative of the given diene side-chain unit to 2-chlorotropone, In each instance, the requisite 2-substituted tropone was obtained directly from these reaction sequences. A similar study was conducted on the corresponding chromium(0) complexes of related tropone and cycloheptatriene-based substrates. In the cases involving metal mediation both thermal and photochemical activation were effective for delivering cycloadducts. The metal-promoted reactions were shown to proceed exclusively via an endo-selective pathway, which is stereocomplementary to the course of the thermal, metal-free reactions. A tandem Cr(0)-promoted 1,5-H shift-[6 pi+2 pi] cycloaddition protocol is also reported with several systems.
Studies on Intramolecular Higher-Order Cycloaddition Reactions
摘要:
Thermal, metal-free, and metal-promoted intramolecular higher-order cycloadditions are described. Substrates in which the tropone (2,4,6-cycloheptatrien-1-one) nucleus is tethered to various diene moieties undergo exo-selective [6 pi + 4 pi] cycloaddition under thermal conditions to afford stereochemically defined tricyclic products. The substrates employed in this study were prepared by addition of the Grignard derivative of the given diene side-chain unit to 2-chlorotropone, In each instance, the requisite 2-substituted tropone was obtained directly from these reaction sequences. A similar study was conducted on the corresponding chromium(0) complexes of related tropone and cycloheptatriene-based substrates. In the cases involving metal mediation both thermal and photochemical activation were effective for delivering cycloadducts. The metal-promoted reactions were shown to proceed exclusively via an endo-selective pathway, which is stereocomplementary to the course of the thermal, metal-free reactions. A tandem Cr(0)-promoted 1,5-H shift-[6 pi+2 pi] cycloaddition protocol is also reported with several systems.
Synthetic studies on the ingenane diterpenes. Inter- and intramolecular [6 + 4] tropone-diene cycloaddition reactions
作者:James H. Rigby、Terry L. Moore、Sushil Rege
DOI:10.1021/jo00362a051
日期:1986.6
Construction of the ingenane core using an Fe(III) or Ti(IV) Lewis acid-catalyzed intramolecular [6+4] cycloaddition
作者:James H. Rigby、Mike Fleming
DOI:10.1016/s0040-4039(02)02159-7
日期:2002.11
A facile entry into the ingenane core using a Lewis acid-catalyzed intramolecular [6+4] cycloaddition has been developed. Ti(IV)- and Fe(III)-based Lewis acids were found to mediate the higher order cycloaddition in good to excellent yield at room temperature. Chiral Ti(IV) Lewis acids were found to induce modest asymmetry in the resultant [6+4] cycloadducts. (C) 2002 Elsevier Science Ltd. All rights reserved.
Studies on Intramolecular Higher-Order Cycloaddition Reactions
作者:James H. Rigby、Sushil D. Rege、Vincent P. Sandanayaka、Margarita Kirova
DOI:10.1021/jo9518009
日期:1996.1.1
Thermal, metal-free, and metal-promoted intramolecular higher-order cycloadditions are described. Substrates in which the tropone (2,4,6-cycloheptatrien-1-one) nucleus is tethered to various diene moieties undergo exo-selective [6 pi + 4 pi] cycloaddition under thermal conditions to afford stereochemically defined tricyclic products. The substrates employed in this study were prepared by addition of the Grignard derivative of the given diene side-chain unit to 2-chlorotropone, In each instance, the requisite 2-substituted tropone was obtained directly from these reaction sequences. A similar study was conducted on the corresponding chromium(0) complexes of related tropone and cycloheptatriene-based substrates. In the cases involving metal mediation both thermal and photochemical activation were effective for delivering cycloadducts. The metal-promoted reactions were shown to proceed exclusively via an endo-selective pathway, which is stereocomplementary to the course of the thermal, metal-free reactions. A tandem Cr(0)-promoted 1,5-H shift-[6 pi+2 pi] cycloaddition protocol is also reported with several systems.