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Wrackmeyer, Bernd ; Shahid, Khadija ; Kempe, Rhett ; Döring, Christian ; Milius, Wolfgang:
Indazaboles : synthesis and molecular structure.
In: Applied Organometallic Chemistry.
Bd. 24
(2010)
Heft 5
.
- S. 398-401.
ISSN 1099-0739
DOI: https://doi.org/10.1002/aoc.1627
Abstract
The reaction of 1-trimethylsilyl-indazole with boranes affords indazaboles accompanied by elimination of trimethysilane. Thus, the two isomers of parent indazabole are formed in a 1:1 ratio using borane in THF (BH3/THF), characterized by NMR spectroscopy in solution (1H, 11B and 13C NMR). In contrast, the analogous reaction with 1,2-bis(tetramethylene)diborane(6) proceeds to give a single isomer of the B-alkylated indazabole via symmetric ring cleavage of the diborane(6), as shown by NMR in solution and X-ray structural analysis in the solid state. The molecular structure is fluxional in solution. In the solid state, the central B2N4 ring adopts a distorted boat conformation. Calculated gas phase geometries of the parent indazaboles and of the B-alkylated indazabole were optimized by DFT methods at the B3LYP/6-311 + G(d,p) level of theory.