Department of Chemistry, Federal University of Lavras, 37200-000 Lavras, MG, Brazil.
J Org Chem. 2012 Sep 7;77(17):7607-11. doi: 10.1021/jo3014885. Epub 2012 Aug 16.
α-Substituted sulfoxides can experience both gauche and anomeric effects, since these compounds have the geometric requirements and strong electron donor and acceptor orbitals which are essential to make operative the hyperconjugative nature of these effects. Indeed, the title effects were calculated to take place for 1,3-oxathiane 3-oxide in polar solution, where dipolar effects are absent or at least minimized, while only the gauche effect is present in 2-fluorothiane 1-oxide. Since the fluorine atom is a suitable probe for structural analysis using NMR, the (1)J(CF) dependence on the rotation around the F-C-S═O dihedral angle of (fluoromethyl)methyl sulfoxide was evaluated; differently from 1,2-difluoroethane and fluoro(methoxy)methane, this coupling constant is at least not exclusively dependent on dipolar interactions (or on hyperconjugation). Because of the nonmonotonic behavior of the (1)J(CF) rotational profile, this coupling constant does not appear to be of significant diagnostic value for probing the conformations of α-fluoro sulfoxides.
α-取代亚砜可以同时经历 gauche 和 anomeric 效应，因为这些化合物具有必要的几何要求和强电子供体和受体轨道，这些是使这些效应的超共轭性质起作用所必需的。实际上，标题效应被计算为在极性溶液中 1,3-氧杂硫杂环己烷 3-氧化物发生，其中不存在偶极效应或至少最小化，而在 2-氟噻烷 1-氧化物中仅存在 gauche 效应。由于氟原子是使用 NMR 进行结构分析的合适探针，因此评估了（1）J（CF）对（氟甲基）甲基亚砜围绕 F-C-S═O 二面角旋转的依赖性; 与 1,2-二氟乙烷和氟（甲氧基）甲烷不同，该偶合常数至少不是仅依赖于偶极相互作用（或超共轭）。由于（1）J（CF）旋转轮廓的非单调行为，该偶合常数似乎对于探测α-氟亚砜的构象没有重要的诊断价值。
