Synthesis 2008(8): 1288-1296  
DOI: 10.1055/s-2008-1042941
PAPER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of All Possible Stereoisomers of α-Branched [2.2]Paracyclophanyl­alkylamines

Dieter Enders*, Stephan Noll, Gerhard Raabe, Jan Runsink
Institute of Organic Chemistry, RWTH Aachen, Landoltweg 1, 52074 Aachen, Germany
Fax: +49(241)8092127; e-Mail: enders@rwth-aachen.de;
Further Information

Publication History

Received 11 January 2008
Publication Date:
18 March 2008 (online)

Abstract

The synthesis of all four possible stereoisomers of enantiopure and diastereomerically pure or highly enriched α-branched [2.2]paracyclophanylalkylamines is described. Key step is the nucleophilic 1,2-addition of alkyllithium reagents to hydrazones of 4-formyl[2.2]paracyclophane derived from the chiral auxiliaries SAMP/RAMP and RAMBO/SAMBO via chromatographic epimer separation. Reductive N-N bond cleavage of the resulting hydrazines, followed by treatment with benzyloxycarbonyl chloride afforded the N-Cbz-protected diastereo- and enantiopure (de, ee ÷ 99%) or diastereomerically enriched (de = 89-96%) title amines.

12

CCDC 673149 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by e-mailing to data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44(1223)336033.

17

For an alternative synthesis starting from (R p )-4-formyl[2.2]paracyclophane N,N-dimethylhydrazone, see ref. 7.

18

The preparation of this enantiomer was described in a preceding communication, see ref. 7.