Anionic Domino Process for the One-Pot, Diastereoselective Synthesis of Dihydropyranols from β-Nitroalcohols

Abstract

Bringing together β-nitroalkanols and cis-3-hexen-2,5-dione, in the presence of DBU as base and in acetonitrile as solvent, we achieved a one-pot diastereoselective synthesis of dihydropyranol derivatives. The nature of the latter compounds is consistent with the initial formation of a Michael adduct, followed by base-promoted elimination of nitrous acid leading to an allylic alcohol, which, finally, cyclises diastereoselectively to form a hemi-ketal functionality.

nitroalkanols - diastereoselectivity - Michael reaction - dihydropyranols - anionic domino process

References

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15

Selected analytical data for the compounds 5b,d,i.
Compound 5b (cis/trans ratio = 16:84): brown oil. IR: 3401.3, 1710.5, 1659.6, 1560.9, 1099.0 cm^-1. ¹H NMR (CDCl₃): δ = 1.36 (d, 3 H, J = 6.8 Hz), 1.55 (s, 3 H), 2.15-2.37 (m, 1 H), 2.33 (s, 3 H), 2.43 (br s, 1 H), 2.57 (dd, 1 H, J = 17.6, 3.0 Hz), 4.37-4.43 (m, 0.16 H), 4.56-4.72 (m, 0.84 H), 6.75 (br s, 1 H). ¹³C NMR (CDCl₃): δ = 20.2, 25.1, 30.0, 32.8, 65.1, 95.4, 134.1, 141.1, 198.3. Anal. Calcd for C₉H₁₃O₃: C, 63.89; H, 7.74. Found: C, 64.11; H, 7.85. Compound 5d (cis/trans ratio = 15:85): brown oil. IR: 3400.6, 1708.3, 1656.2, 1551.8, 1098.0 cm^-1. ¹H NMR (CDCl₃): δ = 0.97 (t, 3 H, J = 7.1 Hz), 1.35-1.77 (m, 5 H), 1.54 (s, 3 H), 2.15-2.44 (m, 1 H), 2.33 (s, 3 H), 2.59 (dd, 1 H, J = 18.0, 2.9 Hz), 4.36-4.45 (m, 0.15 H), 4.46-4.58 (m, 0.85 H), 6.75 (br s, 1 H). ¹³C NMR (CDCl₃): δ = 14.1, 18.4, 25.0, 29.8, 32.9, 36.3, 68.5, 95.1, 134.3, 140.1, 197.9. Anal. Calcd for C₁₁H₁₇O₃: C, 66.98; H, 8.69. Found: C, 67.14; H, 8.92. Compound 5i (cis/trans ratio = 17:83): brown oil. IR: 3401.7, 1669.3, 1560.0, 1096.3 cm^-1. ¹H NMR (CDCl₃): δ = 1.38 (s, 0.51 H), 1.41 (s, 2.49 H), 1.89-2.02 (m, 3 H), 2.17 (dd, 1 H, J = 17.3, 3.9 Hz), 2.20 (s, 3 H), 2.50 (dd, 1 H, J = 17.7, 3.0 Hz), 2.71-2.81 (m, 2 H), 4.15-4.19 (m, 1 H), 6.60-6.63 (m, 1 H), 7.10-7.30 (m, 5 H). ¹³C NMR (CDCl₃): δ = 22.8, 24.5, 26.5, 30.9, 35.3, 67.7, 97.5, 125.7, 128.1, 128.2, 133.8, 139.7, 141.3, 197.8. Anal. Calcd for C₁₆H₁₉O₃: C, 74.11; H, 7.39. Found: C, 74.32; H, 7.19.