Application Study of N-heterocyclic Carbenes in the Synthesis of Benzazole-phosphine Ligands and Allylic Alkylation Reaction

Author:Ren Wei

Supervisor:yang shang dong

Database:Doctor

Degree Year:2019

Download:13

Pages:161

Size:8816K

Keyword:

N-Heterocyclic Carbenes(NHC)as typical structural features,all carbenes are neutral and possess a pair of lone pair electrons and strong nucleophilic properties.Because of its good catalytic performance,it has been widely applied and developed in the field of organic catalysis.On the other hand,as a new type of electron-rich ligand with strong σ-donor and comparatively weak π-acceptor properties which displays excelent stability for air and oxidant.N-Heterocyclic carbenes are often substituted for phosphine ligands and are widely used in transition-metal-catalyzed cross-coupling reactions dues to the complexes formed by N-heterocyclic carbenes with metals have good catalytic properties.Therefore,it is particularly important to further design and synthesize novel N-Heterocyclic Carbenes and explore their applications in other reactions.Based on these,the following sections will mainly focus on the study of catalytic reactions involved by N-heterocyclic Carbene.1.An efficient strategy for the synthesis of benzazole-phoshpine ligand precursors via N-heterocyclic carbene catalyzed the aerobic oxidative cyclization reaction has been performed and displayed a broader functional group tolerance and high atom economy.The efficacy of this transformation has been further applicated in benzazole-phoshp ine ligand systhesis.2.Allylic C-H alkylation of alylbenzene with α-cyano-phosphate ester has been achieved via Pd(II)/N-Heterocyclic carbenes(NHC)under the mild reaction conditions and provides the corresponding linear alylation product in moderate to good yields.This reaction establishes a new method to construct β-amino phosphonic acid derivatives with tertiary phosphonates.In addition,the α-monoallylation of nitriles have also easily obtained by the simple transformations from the alkylation products under mild conditions.3.The Palladium-N-heterocyclic carbene(NHC)-catalyzed alylic alkylation of various pronucleophiles with alkynes has been accomplished under mild conditions.The protocol exhibits broad functional group compatibility and high atom economy.Moreover,the catalytic process avoids the use of external oxidants and acid as additives.Furthermore,the successfully transformations of the functionalized alylation products to various versatile skeletons were achieved,which demonstrated the potential application utility of this synthetic protocol.