期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 15, 期 29, 页码 7192-7202出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200900575
关键词
Grignard reaction; heterocycles; insertion; regioselectivity; zinc
资金
- Fonds der chemischen Industrie
- ERC (European Research Council)
- DFG
- SFB749
The presence of LiCl considerably facilitates the insertion of magnesium into various aromatic and heterocyclic bromides. Several functional groups, such as -OBoc, -OTs, -Cl, -F, -CF3, -OMe, -NMe2, and -N2NR2, are well tolerated. The presence of a cyano group leads in some cases to competitive reduction of the organic halide to the corresponding ArH compound. The presence of sensitive groups such as methyl or ethyl ester is tolerated upon in situ trapping of the intermediate magnesium reagent with ZnCl2. In the case of di- or tribromoaryl derivatives, directing groups such as -OPiv, -OTs, -N2NR2, or -OAc orient the zinc insertion (Zn/LiCl) to the ortho-position, while the reaction with Mg/LiCl or Mg/LiCl/ZnCl2 leads to regioselective insertion into the para-carbon-bromine bond. Large-scale experiments (20-100 mmol) for all of the metalation procedures are described. This method can also be applied to the preparation of functionalized benzylic zinc reagents from benzylic chlorides.
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