Hetero-Diels-Alder reactions of 2H-phospholes with aldehydes.
Transient 2-phenyl-3,4-dimethyl-5H-phosphole reacts at 150 degrees C with aldehydes RCH=O to give the corresponding [4 + 2] P-O cycloadducts with endo- (major) and exo-R-substituents. The cycloaddition with alpha,beta-unsaturated aldehydes takes place both at the C=O (major) and C=C bonds. Upon heating under reduced pressure, the benzaldehyde cycloadduct dissociates to give back the 2H-phosphole, which either dimerizes, is trapped by diphenylacetylene, or is deprotonated by (t)BuOK.
Toullec
Patrick
P
Laboratoire 'Hétéroéléments et Coordination' UMR CNRS 7653, DCPH, Ecole Polytechnique, 91128 Palaiseau Cedex, France.
Ricard
Louis
L
Mathey
François
F