Synlett 2008(9): 1349-1352  
DOI: 10.1055/s-2008-1072786
LETTER
© Georg Thieme Verlag Stuttgart · New York

Enantiomerically Pure Cyclopropylamines via C-B to C-N Conversion

Jörg Pietruszka*, Gemma Solduga
Institut für Bioorganische Chemie, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, Im Stetternicher Forst, Geb. 15.8, 52426 Jülich, Germany
Fax: +49(2461)616196; e-Mail: j.pietruszka@fz-juelich.de;
Further Information

Publication History

Received 6 March 2008
Publication Date:
07 May 2008 (online)

Abstract

For the first time cyclopropyltrifluoroborates have been utilized to form cyclopropylamines in a one-pot procedure. The scope was not only demonstrated by successfully reacting various racemic cis- and trans-2-substituted cyclopropanes as well as azides, but also by applying the sequence to enantiomerically pure building blocks. An approach to tranylcypromine as well as belactosin A is outlined.

13

General Procedure for the C-B to C-N Conversion
Under an atmosphere of dry nitrogen, the trifluoroborate 3 (1 equiv) was suspended in a mixture of toluene (10 mL/mmol trifluoroborate 3) and MeCN (2.5 mL/mmol trifluoroborate 3). Then, SiCl4 (1 M in CH2Cl2, 2 equiv) was added at r.t. and stirred for 20 min. The corresponding azide 5 (1.4 equiv) was added and the reaction mixture was stirred at r.t. or 40 °C for 5-15 h (depending on the azide used). The reaction was quenched with H2O (10 mL/mmol trifluoroborate 3), and the layers were separated. The organic layer was extracted with HCl (1 M; 5 × 10 mL/mmol trifluoroborate 3). The combined aqueous layers were strongly basified with aq KOH (40%). The amine was extracted with Et2O (4 × 50 mL/mmol trifluoroborate 3). The combined ether layers were dried over Na2CO3. The solvent was removed under reduced pressure.