Chemoselective Photorearrangements of Diazinobarrelenes. Deuterium Labeling Study

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• 作者：Ann-Cheng Chen ; Gary J. Chuang ; Nelson R. Villarante ; Chun-Chen Liao
• 刊名：Journal of Organic Chemistry
• 出版年：2007
• 出版时间：December 7, 2007
• 年：2007
• 卷：72
• 期：25
• 页码：9690 - 9697
• 全文大小：184K
• 年卷期：v.72,no.25(December 7, 2007)
• ISSN：1520-6904

文摘

16795n00001>Chemoselective photorearrangements of pyrazino-, quinoxalino-, and benzoquinoxalinobarrelenes wereinvestigated by deuterium-labeling experiment. Photolysis of pyrazinobarrelene 4 and quinoxalinobarrelene5 with 300 nm region light under either direct or sensitized conditions afforded semibullvalenes 7 and 8,respectively; benzoquinoxalinobarrelene 6 was inert to both reaction conditions. Irradiation of deuteratedpyrazinobarrelene 4-d₄ and quinoxalinobarrelene 5-d₄ afforded deuterated semibullvalenes 7-d₄-A-7-d₄-F and 8-d₄-A-8-d₄-F, respectively. Of the two a priori possibilities of bridging, the deuterium-labelingexperiment has shown that deuterated pyrazinobarrelene 4-d₄ afforded 98% (C₆D₆) and 95% (CD₃CN)of semibullvalenes generated through aryl-vinyl (A-V) bridging, whereas the quinoxalinobarrelene 5-d₄furnished 79% (C₆D₆) and 71% (CD₃CN) of semibullvalenes generated through vinyl-vinyl (V-V)bridging. The contrasting photochemical behavior of heteroarene-fused barrelenes 4-6 was explainedqualitatively in terms of triplet energy minimization and relative stability of diradicaloid intermediates.