Effect of Sulfur Oxidation on the Transmission Mechanism of (4)J(HH) NMR Coupling Constants in 1,3-Dithiane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Long-range (4)J(HH) couplings in 1,3-dithiane derivatives are rationalized in terms of the effects of hyperconjugative interactions involving the S=O group. Theoretical and experimental studies of (4)J(HH), couplings were carried out in 1,3-dithiane-1-oxide (2), cis-1,3-dithiane-1,3-dioxide (3), 1,3-dithiane-1,1,3-trioxide (4), and 1,3-dithiane-1,1,3,3-tetraoxide (5) compounds. Hyperconjugative interactions were studied with the natural bond orbital, NBO, method. Hyperconjugative interactions involving the LPO, oxygen lone pair and sigma*(C2-S1) and sigma*(S1-C6) antibonding orbitals yield an increase of (4)J(Hcq - Hcq) couplings. Long-range (4)J(Ha-Hax), couplings were also observed between hydrogen atoms in axial orientation, which are rationalized as originating in hyperconjugative interactions involving the bonding sigma(C6-Hax) and antibonding sigma*(S=O) orbitals. The symmetry for orbital interactions is possible only when the S=O group is in the axial orientation.1131126472651Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CONICET [PIP 5119/05]UBATEC [X047]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [06/03980-2, 05/59649-0]CONICET [PIP 5119/05]UBATEC [X047