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

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

References

• For reviews see:
• 1a Gibson DH. De Puy CH. Chem. Rev.  1974,  74:  605 
• 1b Kulinkovich OG. Chem. Rev.  2003,  103:  2597 
• 2 Kozyrkov YuYu. Kulinkovich OG. Synlett  2002,  443 
• 3a Kulinkovich OG. Sviridov SV. Vasilevskii DA. Savchenko AI. Pritytskaya TS. J. Org.Chem. USSR (Engl. Transl.)  1991,  27:  250 
• 3b Kulinkovich OG. Vasilevskii DA. Savchenko AI. Sviridov SV. J. Org. Chem. USSR (Engl.Transl.)  1991,  27:  1249 
• For reviews see:
• 4a Kulinkovich OG. de Meijere A. Chem. Rev.  2000,  100:  2789 
• 4b Breit BJ. Prakt. Chem.  2000,  342:  211 
• 4c Kulinkovich OG. Pure Appl. Chem.  2000,  72:  1715 
• 5a For preparation of mesylates see: Ollivier J. Dorizon P. Piras PP. de Meijere A. Salaün J. Inorg. Chim. Acta  1994,  222:  37 
• 5b For preparation of tosylates see: Fieser LF. Fieser M. Reagents for Organic Synthesis   Vol 1.:  Wiley; New York: 1967.  p.1179 
• 10a Julia M. Julia S. Guegan SY. Bull. Soc. Chim. Fr.  1960,  1072 
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6

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.

7

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).

8

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.

9

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).