Stereoselective alkenylation of aldehydes with phosphorus carbanions: Preparation of E- and Z-2-alkoxy- and 2-aryloxy-2-alkenoates

Eighteen phosphorus-based alkenylation reagents 1a–6c were synthesized and condensed with n-butyraldehyde 7a and benzaldehyde 7f. They were condensed with the aldehydes 7b-e,g-n to produce 2-methoxy-2-alkenoates 8a-n and 2-phenoxy-2-alkenoates 9a-n. A discussion on different selectivities for the al...

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Bibliographic Details
Published in:Tetrahedron 1997-12, Vol.53 (50), p.17097-17114
Main Authors: Seneci, Pierfausto, Leger, Isabelle, Souchet, Michel, Nadler, Guy
Format: Article
Language:English
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Summary:Eighteen phosphorus-based alkenylation reagents 1a–6c were synthesized and condensed with n-butyraldehyde 7a and benzaldehyde 7f. They were condensed with the aldehydes 7b-e,g-n to produce 2-methoxy-2-alkenoates 8a-n and 2-phenoxy-2-alkenoates 9a-n. A discussion on different selectivities for the alkenylation reagents under different experimental conditions (base, solvent, temperature), the influence of the aldehydes on the geometrical outcome (electron rich or poor substituents, steric hindrance) and the selection of the most E- and Z- selective reaction conditions for each class of aldehydes are reported. Namely, triphenyl phosphorium salt 1a at RT in THF with DBU was better for Z-selectivity while trifluoroethylphosphonates 5b, 6b and 6c at −78° in THF with KN(SiMe 3) 2 were better for E-selectivity. Graphic
ISSN:0040-4020
1464-5416
DOI:10.1016/S0040-4020(97)10149-1