1,3-bis(diarylmethylidene)-2-methylidenecyclohexanes in cycloaddition and cyclodimerization reactions. The role of stereoelectronic factors.
Cycloaddition and cyclodimerization reactions of 1,3-dibenzylidene- and 1,3-bis(p-methoxybenzylidene)-2-methylidenecyclohexanes, i.e., the diaryltrienes with fixed S-cis-configurations of exocyclic double bonds are studied. These compounds undergo in situ cyclodimerization of the [4 + 2]-type upon dehydration of the precursor tertiary alcohols and form endo-adducts in the Diels-Alder reaction with N-phenylmaleimide. In the presence of CF3COOH, acid-catalyzed cyclodimerization takes place leading to methylidene-substituted spirocyclodimers, which undergo intramolecular cyclization upon prolonged contact with CF3COOH to form a fused carbocyclic system containing a central, 'three-petal' fragment of six-membered rings.
Klimova
Elena I
EI
Universidad Nacional Autónoma de México, Facultad de Química, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., México. klimova@servidor.unam.mx
Martínez García
Marcos
M
Klimova
Tatiana
T
Ortega
S Hernandez
SH
Bakinovsky
Leon V
LV