Palladium-Catalyzed Cascade Reaction of 2-Amino-<i>N</i>′-arylbenzohydrazides with Triethyl Orthobenzoates To Construct Indazolo[3,2-<i>b</i>]quinazolinones
                                
                                    
                                        作者:Weiguang Yang、Rui Qiao、Jiuxi Chen、Xiaobo Huang、Miaochang Liu、Wenxia Gao、Jinchang Ding、Huayue Wu                                    
                                    
                                        DOI:10.1021/jo5024848
                                    
                                    
                                        日期:2015.1.2
                                    
                                    A palladium-catalyzed sequential cyclization/C-H activation cascade reaction of 2-amino-N'-arylbenzohydrazides with triethyl orthobenzoates has been developed, providing indazolo[3,2-b]quinazolinones in good to high yields. Two key intermediates of the reaction, 2-phenyl-3-(phenylamino)quinazolinone and C-H insertion palladacycle, were isolated, and their structures were unambiguously confirmed by X-ray crystallography. This method represents an unprecedented example of a halogen-free protocol to access indazolo[3,2-b]quinazolinones. Moreover, this chemistry also provides a useful tool for the discovery of fluorescent materials.