NbCl₅: A Novel Lewis Acid in Allylation Reactions

Abstract

Allylation reactions promoted by niobium pentachloride are described. Allylstannanes were added to aromatic and aliphatic aldehydes and aromatic imines in good yields. Excellent syn dia­stereoselectivities were obtained in the addition of (E)-cinnamylstannane to benzaldehyde (49:1) and in the addition of crotylstannane to N-benzylideneaniline (46:1).

Key words

allylation - homoallylic compounds - stereoselectivity - niobium pentachloride - Lewis acids

References

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17

¹H NMR (CDCl₃) syn: δ = 1.94 (br, 1 H), 3.63 (t, 1 H, J = 8.0 Hz), 4.78-5.04 (m, 3 H), 5.89 (ddd, 1 H, J = 7.8, 10.3, 18.1 Hz), 7.01-7.38 (m, 10 H). For comparison, see ref. [27]

21

The choice for CH₂Cl₂ was based on the fact that the reaction in this solvent could be run at lower temperature (-78 °C) as compared to CH₃CN.

26

For a complete discussion of the possible transition states geometries, see ref. [24]