Designing Fluorinated Cinchona Alkaloids for Enantioselective Catalysis: Controlling Internal Rotation by a Fluorine-Ammonium Ion gauche Effect (φNCCF)
作者:Eva-Maria Tanzer、W. Bernd Schweizer、Marc-Olivier Ebert、Ryan Gilmour
DOI:10.1002/chem.201102859
日期:2012.2.13
The C9 position of cinchona alkaloids functions as a molecular hinge, with internal rotations around the C8C9 (τ1) and C9C4′ (τ2) bonds giving rise to four low energy conformers (1; anti‐closed, anti‐open, syn‐closed, and syn‐open). By substituting the C9 carbinol centre by a configurationally defined fluorine substituent, a fluorine‐ammonium ion gauche effect (σC−H→σC−F*; Fδ−⋅⋅⋅N+) encodes for two
的金鸡纳生物碱功能C9位置作为分子的铰链,与周围的C8内部旋转 C9(τ 1)和C9 C4'(τ 2)键从而产生四个低能量构象(1 ;抗-封闭,抗-打开,同步关闭和同步打开)。通过由构型上定义的氟取代基,氟铵离子代替C9甲醇中心笨拙效应(σ C-H →σ C-F *;˚F δ- ⋅⋅⋅N +)两个编码的四个可能的构象异构体(2)。这部分解决了长期存在的仅依靠氟构象效应来控制基于氰基鎓盐的催化剂内部旋转的问题。