Cooperative Noncovalent Interactions Lead to a Highly Diastereoselective Sulfonyl-Directed Fluorination of Steroidal α,β-Unsaturated Hydrazones

A series of steroidal α,β-unsaturated
hydrazones is
presented whose behavior and reactivity are governed by various types
of weak C–H hydrogen bonds. Several interesting features in
a representative X-ray crystal structure and 1H NMR spectrum
are examined that provide evidence for a unique bifurcated intramolecular
C–H interaction. Moreover, these steroid derivatives undergo
functionalization in the form of a highly regio- and stereoselective
fluorination; the sulfonyl oxygen atoms are proposed to direct the
fluorinating reagent through C–H hydrogen bonds.

本文报道了一系列甾体α,β-不饱和腙（steroidal α,β-unsaturated hydrazones），其行为与反应性受多种类型的弱C-H氢键调控。通过对代表性X射线晶体结构（X-ray crystal structure）与核磁共振氢谱（1H NMR spectrum）中的若干特征展开分析，我们获得了独特的分叉型分子内C-H氢键相互作用的实验证据。此外，这类甾体衍生物可发生高度区域及立体选择性的氟化官能化反应；研究认为，磺酰氧原子可通过C-H氢键引导氟化试剂（fluorinating reagent）参与反应。