Jm. Coxon et Rt. Luibrand, TRANSITION-STATE HYPERCONJUGATION AS A CAUSE OF PI-FACIAL SELECTION IN CYCLOHEXANONES, Tetrahedron letters, 34(44), 1993, pp. 7097-7100
Ab initio and semiempirical calculations of the transition states of c
yclohexanone reduction by AlH3 show bond length changes and molecular
orbitals consistent with hyperconjugative stabilisation. Both electron
ic and torsional effects contribute to facial selection.