Hydrogen bonding and steric effects on rotamerization in 3,4-alkylenedioxy-, 3-alkoxy- and 3,4-dialkoxy-2-thienyldi(tert-butyl)methanols: an NMR, IR and X-ray crystallographic studyElectronic supplementary information (ESI) available: NMR data; activation parameters for rotation; MMFF94 steric energies and alkoxy group geometries; thermodynamic data; quantum mechanical calculations of geometries; bond lengths, bond angles and torsion angles of 8A-Et; NMR and IR data on new compounds. See http://www.rsc.org/suppdata/p2/b1/b109612p/
作者:John S. Lomas、Alain Adenier、Kun Gao、François Maurel、Jacqueline Vaissermann
DOI:10.1039/b109612p
日期:2002.1.23
largely determined by steric effects but intramolecular hydrogen bonding in the anti isomer contributes to the variation of the anti → syn rotation barrier. A single crystal X-ray diffraction study of the anti-3,4-diethoxy derivative shows that the orientation of the 3-alkoxy group is very different from that in anti-3-methoxy-2-thienyldi(1-adamantyl)methanol. Molecular mechanics and quantum mechanical calculations
的平衡常数的抗 ↔ 顺rotamerization(反:分子内氢键键合的羟基; syn:“免费”羟基3,4-亚烷基二氧基-,3-烷氧基-和3,4-二烷氧基-2-噻吩基二(叔丁基)甲醇的-)取决于3,4-亚烷基二氧基或烷氧基和溶剂, 氢键 溶剂 例如DMSO和 吡啶支持顺式异构体。平衡常数([ syn ] / [ anti ])在氯仿 和 苯降低的顺序:3,4-OCH 2 O-,3,4-O-(CH 2)2 O-,3- OME,3- OET,3,4-(OME)2 ≈3-O我-Pr 3,4-(OEt)2,范围超过约2.5个数量级。IR OH拉伸频率的变化和核磁共振 哦 质子反异构体的位移表明分子内氢键以大致相同的顺序增加。该SYN → 抗旋转屏障二甲基亚砜随取代基的大小和数量增加。3,4-亚甲基二氧基噻吩衍生物的势垒(17.5 kcal mol -1)比所有其他衍生物(21.0-22.3 kcal