Substitution of Two Fluorine Atoms in a Trifluoromethyl Group: Regioselective Synthesis of 3-Fluoropyrazoles
作者:Kohei Fuchibe、Masaki Takahashi、Junji Ichikawa
DOI:10.1002/anie.201206946
日期:2012.11.26
Replacing the fluorine: 3‐Fluorinated pyrazoles were regioselectively synthesized by sequential substitution reactions of 2‐trifluoromethyl‐1‐alkenes (see scheme). SN2′‐type reactions of 2‐trifluoromethyl‐1‐alkenes with deprotonated tert‐butoxylcarbonyl‐ or arylhydrazines afforded 1,1‐difluoro‐1‐alkenes, which were tosylated and then treated with NaH to give the desired 3‐fluoropyrazoles.
取代氟:通过2-三氟甲基-1-烯烃的顺序取代反应区域选择性地合成3-氟代吡唑(参见方案)。2-三氟甲基-1-烯烃与去质子化的叔丁氧羰基羰基或芳基肼的S N 2'型反应生成1,1-二氟-1-烯烃,将其甲苯磺酸化,然后用NaH处理得到所需的3-氟吡唑。