6,6-Dicyanopentafulvenes: Electronic Structure and Regioselectivity in [2 + 2] Cycloaddition鈥揜etroelectrocyclization Reactions

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• 作者：Aaron D. Finke ; Oliver Dumele ; Michal Zalibera ; Daria Confortin ; Pawel Cias ; Govindasamy Jayamurugan ; Jean-Paul Gisselbrecht ; Corinne Boudon ; W. Bernd Schweizer ; Georg Gescheidt ; Fran莽ois Diederich
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：October 31, 2012
• 年：2012
• 卷：134
• 期：43
• 页码：18139-18146
• 全文大小：451K
• 年卷期：v.134,no.43(October 31, 2012)
• ISSN：1520-5126

文摘

We present an investigation of the electronic properties and reactivity behavior of electron-accepting 6,6-dicyanopentafulvenes (DCFs). The electron paramagnetic resonance (EPR) spectra of the radical anion of a tetrakis(silylalkynyl) DCF, generated by Na metal reduction, show delocalization of both the charge and unpaired electron to the nitrogens of the cyano moieties and also, notably, to the silicon atoms of the four alkynyl moieties. By contrast, in the radical anion of the previously reported tetraphenyl DCF, coupling to the four phenyl rings is strongly attenuated. The data provide physical evidence for the different conjugation between the DCF core and the substituents in both systems. We also report the preparation of new fulvene-based push鈥損ull chromophores via formal [2 + 2] cycloaddition鈥搑etroelectrocyclization reaction of DCFs with electron-rich alkynes. Alkynylated and phenylated DCFs show opposite regioselectivity of the cycloaddition, which can be explained by the differences in electronic communication between substituents and the DCF core as revealed in the EPR spectra of the radical anions.