A 1,1‐Carboboration Route to Bora‐Nazarov Systems |
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| Authors: | Fang Ge Fatma Türkyilmaz Dr Constantin G Daniliuc Melanie Siedow Prof?Dr Hellmut Eckert Dr Gerald Kehr Prof?Dr Gerhard Erker |
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| Institution: | 1. Organisch-Chemisches Institut, Universit?t Münster, Münster, Germany;2. Institut für Physikalische Chemie, Universit?t Münster, Münster, Germany |
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| Abstract: | Hydroboration of the conjugated enynes 1 a and 1 b with Piers’ borane HB(C6F5)2] gave the respective dienylboranes trans‐ 2 c and trans‐ 2 d . Their photolysis resulted in the formation of the dihydroborole products 3 c and 3 d . Both were converted to their pyridine adducts 5 c and 5 d , respectively. Compounds 3 c and 5 c,d were characterized by X‐ray diffraction. The reaction of the bis(enynyl)boranes 6 a and 6 b with B(C6F5)3 resulted in the formation of the dihydroboroles 7 a and 7 b , respectively. This reaction is thought to proceed by 1,1‐carboboration of one of the enynyl substituents at boron to generate the dienylborane intermediates 8 a / 8 b , followed by thermally induced bora‐Nazarov ring‐closure and subsequent stabilizing 1,2‐pentafluorophenyl group migration from boron to carbon. Compound 7 a was characterized by X‐ray diffraction and solid‐state 11B NMR spectroscopy. |
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| Keywords: | alkenylboranes boron carboboration heterocycles ring closure |
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