Z. Naturforsch. 2014, 69b, 1357 – 1364
1,1-Carboboration Reactions of Strongly Electrophilic 2-Borylethyl Thioethers
Christina Eller, Bastian Billmann, Constantin G. Daniliuc, Gerald Kehr, and Gerhard Erker
Organisch-chemisches Institut der Westfälischen Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
Reprint requests to Prof. Dr. G. Erker. Fax: +49-251-8336503. E-mail: erker@uni-muenster.de
Received August 22, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of this 80th birthday
The RSCH2CH2B(C6F5)2 boranes 3a (R = Ph) and 3b (R = Et) were in situ generated by HB(C6F5)2 hydroboration of the respective vinylthioethers. Their treatment with R1 −C≡C–SiMe3 acetylenes resulted in clean 1,1-carboboration to give the respective RSCH2CH2-substituted alkenylboranes 4 (3 examples). Likewise, the reagents 3 underwent 1,1-carboboration with the acetylenes Ar2P–C≡C–SiMe3 to give the tetrasubstituted alkenylboranes 6, featuring a geminal pair of RSCH2CH2/B(C6F5)2 substituents at one carbon atom and the Me3Si/PAr2 pair at the other (3 examples). The compounds 6 feature an internal B⋯P interaction. The conceptually related Mes2PCH2CH2B(C6F5)2 borane (2) does not undergo 1,1-carboboration with ArS–C≡C–SiMe3 but forms the 1,2-P/B-FLP addition product 7 to the acetylene instead. Compounds 4a, 4c, 6a, and 7 were characterized by X-ray diffraction.
Key words: Boron, Sulfur, Alkenylboranes, Frustrated Lewis Pairs (FLPs)
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