Cycloadditions dipolaires 1,3. XXIX. Addition de deux esters nitroniques isomères à diverses défines. Etude de la régiosélectivitè et du mode d'approche du dipolarophile par le dipôle

1,3-Dipolar cycloaddition of two geometrical isomers of nitronic esters to some mono, di and trisubstituted olefines was studied. For each reaction only one orientation of the cycloaddition was observed which is in good agreement with theoretical predictions. The modes of approach of these dipolarophiles by the two nitronic esters were established in most cases. They are discussed in terms of secondary interactions of the frontier orbitals of the reactants.