Stereoelectronic control of additions of vinylmagnesium bromide to 1-methyl- and 3-methylpentacyclo[5.4.0.0(2,6)-.0(3,10).0(5.9)]undecane-8,11-diones and to 1-methylhexacylo[10.2.1.0.0(2,11).0(4,9).0(4,14).0(9,13)]pentadeca-5,7-die ne-3,10-dione

摘要

Grignard addition of excess vinylmagnesium bromide to 1-methyl- and 3-methylpentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-diones (1a and 1b, respectively) and to 1-methylhexacyclo[1.0.2.1.0(2,11).0(4,9).0(4,14).0(9,13)]pentadeca-5,7-die ne-3,10-dione (4) each proceed regiospecifically to afford a single hemiketal adduct (i.e., 2a, 3a, and 5a, respectively). The structure of each of the three reaction products was established unequivocally via application of X-ray crystallographic methods. Relative energies for the model transition states obtained from geometry optimizations at the Hartree-Fock level of theory in basis set 3-21G(d) indicate that these reactions are kinetically controlled. [References: 29]