| Summary: | 碩士 === 中國文化大學 === 應用化學研究所 === 90 === The competition among 〔4+2〕,〔6+4〕,〔8+2〕,and〔8+6〕cycloadditions, all symmetry allowed thermal processes, has prompted much investigation.
In order to determine the product selectivity, such as the diastereoselectivity, periselectivity, and regioselectivity, which is governed by steric effects and/or electronic effects of the exocyclic substituents on the fulvenes and substituents on the phenyl groups of the azaheptafulvenes, the cycloadditions of electron-rich disubstituted fulvenes 1a,b with azaheptafulvenes (13a-c ) are investigated.
The reaction of azaheptafulvenes 13a-c with the less hindered 6,6-dimethylfulvene (1a) at lower temperature (80℃) afforded exclusively 〔6+4〕 adducts 15a-c . At higher temperature(140 ℃) afforded mainly〔4+2〕adducts 16a-c ,along with traces of 〔6+4〕 adducts 15a-c.
When the reaction of azaheptafulvenes 13a-c with 6-isopropyl-6-methylfulvene (1b) at lower temperature (80℃) afford exclusively 〔6+4〕 adducts 17a-c and 18a-c . At higher temperature(140℃) afforded mainly〔4+2〕adducts 19a-c ,along with traces of 〔6+4〕 adducts 17a-c and 18a-c.
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