substituted phenyl rings of benzophenone ketals in lithiation reactions proved to be a useful tool to study both ortho-directing ability and long-range effects of the substituents. The regioselectivities observed in the reaction of benzophenone ketals having one or two chloro substituents in one of the aryl rings with butyllithium complexed to N,N,N′,N″,N″-pentamethyldiethylenetriamine demonstrate the
increased interest in this compound family. However, the literature of the closely related 2,3,4-benzothiadiazepine 2,2-dioxides is rather scarce. Earlier we elaborated a synthesis of 5-aryl congeners variously substituted at the aromatic ring. In the present study, a new synthetic route was investigated via highly versatile intermediates, to extend the reaction to a wider aromatic substitution pattern and
Lithiation of 2-Aryl-2-(chloroaryl)-1,3-dioxolanes and Its Application in the Synthesis of Newortho-Functionalized Benzophenone Derivatives
作者:Gyula Lukács、Márta Porcs-Makkay、Gyula Simig
DOI:10.1002/ejoc.200400335
日期:2004.10
2-Aryl-2-(chloroaryl)-1,3-dioxolanes 4 were lithiated ortho to the ketal group of the chloroaryl ring by treatment with butyllithium in THF between −78 and 0 °C. The site selectivity of some of the deprotonation reactions was rationalized by the long-range effect of the 4-chloro substituent. The lithio species thus generated were treated with various electrophiles to give ortho-functionalized benzophenone