An Orbital Phase Theory

Abstract

Cyclic orbital interactions are contained in non-cyclic conjugation as well as cyclic conjugation. For effective interactions, the orbitals are required to meet simultaneously the phase continuity conditions: (1) out of phase relation between electron-donating orbitals; (2) in phase relation between electron-accepting orbitals and between electron-donating and -accepting orbitals. The orbital phase theory is applicable to diverse chemical phenomena of non-cyclic conjugate systems, e.g., relative stabilities of non-cyclic isomers, and selectivities of the reactions through non-cyclic transition structures. The orbital phase theory also includes the rules for cyclic systems, i.e., the Wooward-Hoffmann rule for stereoselection of organic reactions and the Hueckel 4n + 2p electron rule for aromatic molecules. Derivation and applications of the orbital phase theory are reviewed.

Contribution of Solvents to Geometrical Preference in the Z/E Equilibrium of N-Phenylthioacetamide

“…To elucidate the origin of the effect of N -methylation on Z / E thioamide preference (Table ), we analyzed the electronic structures of the molecules in terms of the orbital interactions of thioacetamides ( 1a/3a and 1 b /3b ) by means of bond model analysis (BMA) (Tables S2–S4). , The interbond energies (IBEs), including both occupied-occupied orbitals and occupied-vacant orbitals, were used to evaluate the bond interactions in the molecules. The IBEs were calculated for (1) vicinal bond interactions with respect to the thioamide N–C­(S) bond, that is, between σ­(C1–C2)/σ­(C1–S) and σ­(N–H)/σ­(N–C­(Ar)) (they are in a vicinal relation; see Figure ), (2) conjugation between n (N) and CS, n (N) and Ar, and CS and Ar, and (3) repulsive interaction between two substituents attached to the thioamide bond, including all C–C and C–H σ bonds and π orbitals of the aromatic ring.…”

Elucidation of the E-Amide Preference of N-Acyl Azoles

“…We focused on analysis of N -acetyl pyrazole 2 and N -2′,4′,6′-trichlorobenzoyl pyrazole 6b to determine the origin of the E -conformer preference. The electronic structures of the molecules were analyzed using bond model analysis, which is able to evaluate the bond orbital interactions in molecules …”

Requirements of Orbital Phase Continuity Revisited: A FMO Ap-Proach

“…Recently, we reported that the phase of the orbitals 1 , which originates from the wave character of electrons in molecules, plays an essential role in determining reactivity and selectivity. Especially, cyclic orbital interaction 2 , in which a series of orbitals interact in a monocyclic manner, determines the regioselectivity in deprotonation of an indole sidechain 3,4 , diastereoselectivity in pericyclic reactions 5 including the electrocyclic ringopening reaction of 3-substituted cyclobutenes 6,7 , cheletropic reactions 8 and the retro-Nazarov reaction. 9,10 Recently, we reported that diastereoselectivity in the uncatalyzed Mukaiyama aldol reaction 11 and the electrophilic addition of -substituted ethylenes 12 are under the control of cyclic orbital interaction.…”