Nucleophilic Substitution Reactions with the 3-Borane-1,4,5-trimethylimidazol-2-ylidene Anion. – Unexpected Formation of an Imidazabole Isomer
✍ Scribed by Andreas Wacker; Hans Pritzkow; Walter Siebert
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 258 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The nucleophilic carbene 3-borane-1,4,5-trimethylimidazol-dimethoxyborane and HBCl 2 • S(CH 3 ) 2 were used as electrophiles. In both cases only the imidazabole 14a could 2-ylidene anion (1 -) reacts with the electrophiles CH 3 I, (CH 3 ) 3 SiCl, (CH 3 ) 3 SnCl, and the bromodiazaboroline 7 to be isolated. Imidazole 5, the imidazole borane adduct 3a and the imidazabole 14a were characterized by X-ray structure form the 2-substituted imidazoles 4, 5, 6, and 8. With triethylborane, the anionic carbene borane adduct 9 -is analyses. obtained. An unexpected result was achieved when chloro- [a] Anorganisch-Chemisches Institut der Universität, found in the 1 H-NMR spectrum at δ ϭ 0.49 and in the 13 C-Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany NMR spectrum at δ ϭ Ϫ5.1. The signal for the C2 carbon