Switchable C-H Alkylation of Aromatic Acids with Maleimides in Water and Air:Carboxyl as a Diverse Directing Group

【作者】 Fan Pu； Zhong-Wen Liu； Lin-Yan Zhang； Juan Fan； 石先莹；

【Author】 Fan Pu;Zhong-Wen Liu;Lin-Yan Zhang;Juan Fan;Xian-Ying Shi;Key Laboratory of Syngas Conversion of Shaanxi Province,School of Chemistry and Chemical Engineering,Shaanxi Normal University;

【机构】 Key Laboratory of Syngas Conversion of Shaanxi Province,School of Chemistry and Chemical Engineering,Shaanxi Normal University； 陕西师范大学；

【摘要】 As an alternative to the conjugate addition of organometallic reagents to α,β-unsaturated carbonyl compounds,the direct addition of C-H bonds to unsaturated carbon-carbon bonds has been intensively investigated because it offers a more straightforward and economical route to form C-C bonds.1 After the pioneering work of Murai’s group,~2 the chelation-assisted strategy is widely applied to the direct addition of C-H bonds to α,β-unsaturated carbonyl compounds,and improved selectivity has been achieved with the assistance of a directing group such as carbonyl,imine,nitrogen heterocycle,and bidentate 8-aminoquinoline.In the respect of directing groups,carboxyl with the following advantages has been applied extensively in C-H functionalization.It widely exists in organic molecules and can be obtained from many other functional groups readily.The carboxyl group can be easily transformed into diverse functional groups or be removed via decarboxylation after directed C-H functionalization.Herein,a ruthenium(Ⅱ)-catalyzed protocol to access conjugate addition or decarboxylative conjugate addition of aromatic acids with maleimides has been developed.3 A variety of different aryl substituted succinimides were obtained in moderate to excellent yields.It is interesting to note that aromatic acids play a pivotal role in the chemoelectivity but not reaction conditions.Under almost the same reaction conditions,carboxyl can act as either a classical directing group or a traceless directing group,thereby generating two kinds of products,i.e.,2-alkyl substituted benzoic acids and alkyl substituted benzenes.These two reactions proceeded under mild and redox-neutral conditions in neat water under the atmosphere of air,and could be easily scaled up to grams.Noteworthy,although carboxyl as a classical or a traceless directing group has been extensively studied,the reaction pathway controlled by the intrinsic property of aromatic acids but not reaction conditions has never been reported.更多还原

【Abstract】 As an alternative to the conjugate addition of organometallic reagents to α,β-unsaturated carbonyl compounds,the direct addition of C-H bonds to unsaturated carbon-carbon bonds has been intensively investigated because it offers a more straightforward and economical route to form C-C bonds.1 After the pioneering work of Murai’s group,~2 the chelation-assisted strategy is widely applied to the direct addition of C-H bonds to α,β-unsaturated carbonyl compounds,and improved selectivity has been achieved with the assistance of a directing group such as carbonyl,imine,nitrogen heterocycle,and bidentate 8-aminoquinoline.In the respect of directing groups,carboxyl with the following advantages has been applied extensively in C-H functionalization.It widely exists in organic molecules and can be obtained from many other functional groups readily.The carboxyl group can be easily transformed into diverse functional groups or be removed via decarboxylation after directed C-H functionalization.Herein,a ruthenium(Ⅱ)-catalyzed protocol to access conjugate addition or decarboxylative conjugate addition of aromatic acids with maleimides has been developed.3 A variety of different aryl substituted succinimides were obtained in moderate to excellent yields.It is interesting to note that aromatic acids play a pivotal role in the chemoelectivity but not reaction conditions.Under almost the same reaction conditions,carboxyl can act as either a classical directing group or a traceless directing group,thereby generating two kinds of products,i.e.,2-alkyl substituted benzoic acids and alkyl substituted benzenes.These two reactions proceeded under mild and redox-neutral conditions in neat water under the atmosphere of air,and could be easily scaled up to grams.Noteworthy,although carboxyl as a classical or a traceless directing group has been extensively studied,the reaction pathway controlled by the intrinsic property of aromatic acids but not reaction conditions has never been reported.更多还原