Synlett 2002(3): 0423-0426
DOI: 10.1055/s-2002-20456
LETTER
© Georg Thieme Verlag Stuttgart · New York

Catalytic Asymmetric and Stereoselective Synthesis of Vinylcyclopropanes

Swapan Majumdara, Armin de Meijereb, Ilan Marek*a
a Department of Chemistry and Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, Technion City, 32000 Haifa, Israel
Fax: +972(4)82937 09; e-Mail: chilanm@tx.technion.ac.il;
b Institut für Organische Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
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Publikationsverlauf

Received 5 December 2001
Publikationsdatum:
05. Februar 2007 (online)

Abstract

The first sequential catalytic asymmetric carbolithiation reaction of dienyl systems followed by a 1,3-intramolecular elimination leads to (E)- and trans-disubstituted vinylcyclopropanes in moderate to good enantiomeric excesses.

18

Typical Experimental Procedure for the Preparation of 13a from 7: A solution of acetal 7 (1 mmol) in hexane (5 mL) was added to the solution of n-butyllithium (3.3 mmol) in hexane in the presence of 10 mol% of (-)-sparteine (based on starting material) at -10 °C over a period of 20 min. When the carbolithiation reaction was complete (as followed by TLC), the orange reaction mixture was rapidly warmed to room temperature and stirred overnight. Then the reaction mixture was cooled to 0 °C, and an aqueous 1 N HCl solution (10 mL) was added. The organic phase was separated, and the aqueous layer was extracted twice with ether (2 × 10 mL). The combined organic layers were washed with water, dried over MgSO4 and evaporated under reduced pressure (flask being immerged in an icewater bath). The residue was purified by column chromatography over silica gel (60-120 mesh, hexane) to give the desired compound 13a in 53% yield with an enantiomeric excess of 83%.

22

A large excess of (1R, 2R)-N, N’-dimethyl-1,2-diphenylethanediamine was used in order to avoid any kinetic resolution. No starting material was left (see ref. [19] ).

25

Specific rotations for vinylcyclopropane derivatives: 12a [α]D 25 = -13.33 (c 0.60, CHCl3); 12b [α]D 25 = -11.66 (c 1.2, CHCl3); 13a [α]D 25 = -46.6 (c 1.67, CHCl3); 13b [α]D 25 = -23.3 (c 1.2, CHCl3); 14a [α]D 25 = -25.45 (c 1.12, CHCl3); 14b [α]D 25 = -17.5 (c 0.80, CHCl3); 15a [α]D 25 = -8.24 (c 1.7, CHCl3); 15b [α]D 25 = -7.69 (c 1.04, CHCl3); 17 [α]D 25 = -20.0 (c 0.80, CHCl3).