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Synlett 2004(2): 0344-0346  
DOI: 10.1055/s-2003-44987
LETTER
© Georg Thieme Verlag Stuttgart · New York

A Convenient and Stereoselective Method for the Preparation of 2-Substituted 1,3-Alkadienes from 1,2-Disubstituted Cyclopropanols

Yurii Yu. Kozyrkov, Oleg G. Kulinkovich*
Department of Organic Chemistry, Belarusian State University, 4, Skoriny av., Minsk, 220050, Belarus
Fax: +375(17)2264998; e-Mail: kulinkovich@bsu.by;
Further Information

Publication History

Received 22 October 2003
Publication Date:
08 December 2003 (online)

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Abstract

Sulfonates of cis-1,2-disubstituted cyclopropanols are converted into 2-substituted 1,3-alkadienes in moderate to good yields under the action of magnesium perchlorate and triethylamine in diethyl ether. High trans-stereoselectivity was observed for the preparation of the alkadienes with a 1,2-disubstituted double bond. The stereochemical outcome in the reaction is consistent with a ­concerted reaction mechanism involving an Mg(ClO4)2-initiated cationic cyclopropyl-allyl isomerization of the cyclopropyl ­sulfonates which is accompanied by a deprotonation.

Key words

cyclopropanols - sulfonates - ring opening - 1,3-dienes - magnesium perchlorate

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Typical Procedure: Tosyl chloride (2.86 g, 15 mmol) was added at once to a solution of 1-benzyl-2-methylcyclo-propanol (1a, 1.62 g, 10 mmol) in dry pyridine (15 mL) at
0 °C and the mixture was left overnight at r.t. After treatment with ice water (100 mL) and Et2O (3 × 15 mL), the organic phase was washed with 5% H2SO4 (15 mL), aq NaHCO3 (2 × 15 mL) and dried with anhyd Na2SO4. After evaporation of the solvents the residue was purified by column chromatography on silica gel (eluent benzene) to give 1.22 g (51%) of tosylate 2b as a colorless oil.

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1H NMR (400 MHz, CDCl3): Entry 2: δ = 0.47 (t, J = 6.8 Hz, 1 H), 1.16 (d, J = 6.8 Hz, 3 H), 1.35 (dd, J 1 = 10.6 Hz, J 2 = 6.4 Hz, 1 H), 1.52-1.65 (m, 1 H), 2.40 (s, 3 H), 3.05 (d, J = 16 Hz, 1 H), 3.28 (d, J = 16 Hz, 1 H), 7.22 (d, J = 8 Hz, 2 H), 7.30-7.40 (m, 5 H), 7.62 (d, J = 8 Hz, 2 H). Entry 6: δ = 0.19 (t, J = 6.4 Hz, 1 H), 0.87 (t, J = 7.2 Hz, 3 H), 1.05-1.40 (m, 16 H), 1.54 (s, 3 H), 2.43 (s, 3 H), 7.31 (d, J = 8 Hz, 2 H), 7.75 (d, J = 8 Hz, 2 H). Entry 8: 0.18 (t, J = 6.8 Hz,
1 H), 0.85 (t, J = 7.2 Hz, 3 H), 0.87 (t, J = 7.2 Hz, 3 H), 0.98-1.10 (m, 1 H), 1.12-1.55 (m, 19 H), 1.80-1.90 (m, 1 H), 2.43 (s, 3 H), 7.31 (d, J = 8 Hz, 2 H), 7.75 (d, J = 8 Hz, 2 H).

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Typical Procedure: A solution of sulfonate 2b (0.32 g, 1 mmol) in Et2O (1 mL) was added to a mixture of Et3N (0.21 mL, 1.5 mmol), Mg(ClO4)2 (0.67 g, 3 mmol), CH2Cl2 (4 mL) and Et2O (6 mL) at r.t. When the reaction was complete (control by TLC), 2% H2SO4 (10 mL) was added to the reaction mixture and the water layer was extracted with Et2O, the organic layer was washed with sat. NaHCO3 solution (2 × 10 mL) and dried over Na2SO4. After evaporation of the solvent, the residue was purified by column chromatography on silica gel (eluent petroleum ether), yielding 0.10 g (70%) of diene 3a.

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1H NMR (400 MHz, CDCl3): Entry 2: δ = 3.59 (s, 2 H), 4.94 (s, 1 H), 5.09 (d, J = 10.8 Hz, 1 H), 5.20 (s, 1 H), 5.27 (d, J = 17.6 Hz, 1 H), 6.47 (dd, J 1 = 17.6 Hz, J 2 = 10.8 Hz, 1 H), 7.18-7.34 (m, 5 H). Entry 6: δ = 0.92 (t, J = 6.8 Hz, 3 H), 1.20-1.50 (m, 10 H), 1.87 (s, 3 H), 2.14 (m, J = 7 Hz, 2 H), 4.89 (s, 2 H), 5.70 (dt, J 1 = 15.6 Hz, J 2 = 7 Hz, 1 H), 6.17 (d, J = 15.6 Hz, 1 H). Entry 8: 0.87 (t, J = 6.8 Hz, 3 H), 0.92 (t, J = 7.2 Hz, 3 H), 1.25-1.55 (m, 10 H), 2.08 (q, J = 7 Hz, 2 H), 2.19 (t, J = 7.2 Hz, 2 H), 4.85 (s, 1 H), 4.88 (s, 1 H), 5.68 (dt, J 1 = 15.6 Hz, J 2 = 7 Hz, 1 H), 6.06 (d, J = 15.6 Hz, 1 H).