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Observation of a thermally induced Bora-Nazarov cyclization at a phosphole framework
Juri Möbus1,2, Gerald Kehr1, Constantin G Daniliuc1
1Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster (Germany).
Abstract:
The reaction of the bis(enynyl)phosphanes 6 a,b with the electrophilic borane reagents RB(C6 F5 )2 (R=C6 F5 , CH2 CH2 Ph, CH3 ) gave phospholes cleanly in a 1,1-carboboration reaction sequence. Depending on the steric bulk, the resulting 2,5-alkenylphospholes underwent a thermally induced bora-Nazarov type cyclization. The equilibrium situation of these examples of a bora-Nazarov type cyclization was investigated in detail by NMR spectroscopy, X-ray crystal structure analysis, and DFT calculations.
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