The Nucleophilic 5-endo-trig Cyclization of 1,1-Difluoro-1-alkenes: Ring-Fluorinated
Hetero- and Carbocycle Synthesis and Remarkable Effect of
the Vinylic Fluorines on the Disfavored Process
Intramolecular cyclization of β,β-difluorostyrenes bearing an iminomethyl or a diazenyl group at the ortho position: synthesis of 3-fluorinated isoquinoline and cinnoline derivatives
作者:Junji Ichikawa、Yukinori Wada、Hiroyuki Kuroki、Jun Mihara、Ryo Nadano
DOI:10.1039/b712965c
日期:——
the corresponding oximes or imines and (ii) subsequent intramolecular replacement of a vinylic fluorine by the sp(2) nitrogen of the iminomethyl group (HON=CH- or HN=CH-). Beta,beta-Difluorostyrenes bearing an o-diazenyl group (HN=N-), generated by reduction of the corresponding diazonium ions, undergo a similar substitution to afford 3-fluorinated cinnolines.
β,β-Difluorostyrenes bearing tosylamido, hydroxy
ormethylsulfinyl groups at the o-position undergo intramol-ecular
substitution of the nitrogen, oxygen or sulfur withloss of fluorine
via a 5-endo-trigonal process leading to2-fluorinated
heterocyclic systems in high yields.
graphico-Cyano-beta,beta-difluorostyrenes react with organolithiums selectively at the cyano carbon to generate the corresponding sp(2) nitrogen anions, which in turn undergo intramolecular replacement of the vinylic fluorine to afford 3-fluoroisoquinolines. Similarly, the reaction of beta,beta-difluoro-o-isocyanostyrenes with organomagnesiums or -lithiums generates the corresponding sp(2) carbanions on the isocyano carbon. Subsequent cyclization via substitution of the fluorine leads to 3-fluoroquinolines.