Study On Cobalt(Ⅱ)-Catalyzed Oxidative Isocyanide Insertion Reactions

Recently, transition-metal catalytzed isocyanide insertions have been one of the research hotspots in the field of isocyanide chemistry, which are widely used for the construction of heterocycles, total synthesis of natural products, drug discovery and materials science. In this doctoral graduation thesis, we designed a variety of Cobalt(II)-catalyzed or metal free-catalyzed oxidative isocyanide insertion reactions. There are seven parts in this thesis which were described as follow:(1) The novel synthesis of substituted 2-aminobenzimidazoles, 2-aminobenzothiazoles, and 2-aminobenzoxazoles was achieved using cobalt(II) acetate catalyzed isocyanides insertion to o-diaminobenzene, 2-aminobenzenethiol, and 2-aminophenol derivatives. It was found that the reaction proceeded efficiently to give the desired product in up to 95% isolated yields via C-N and C-S(O, N) formation in a single step.(2) Cobalt(II) acetylacetonate-catalyzed isocyanides insertion reactions with amines under ultrasound conditions has been developed, which lead to the synthesis of ureas, thioureas. The intermediate amino methylidyneaminiums, initiated by cobalt(II) acetylacetonate-catalyzed reactions of isocyanides with amines, could be easily trapped by different nucleophiles such as water, sulphur. This method provides a simple, general and practical protocol for the divergent synthesis of ureas, thioureas and azaheterocycles.(3) A novel and efficient cobalt-catalyzed oxidative isocyanide insertion with amines via two C-N bonds formation under ultrasound irradiation conditions has been developed. This protocol provides a simple, clean and general way to synthesize guanidines from simple starting materials under ultrasonic conditions.(4) An I2/CHP mediated isocyanide insertion reactions with readily accessible amines via C-N formation has been described for carbodiimides and 1,3-diazetidine-2,4-diimine derivatives synthesis in moderate to excellent yields. This work not only represented a metal-free strategy for isocyanide insertion with amines, but also provided an efficient approach for the synthesis of carbodiimide and 1,3-diazetidine-2,4-diimine derivatives under mild conditions.(5) A NIS/CHP mediated [4+1]-cycloaddition of isocyanides with in situ generated 1,2-diaza-1,3-dienes from hydrazones under metal-free conditions has been developed. This protocol provides a new, atom efficient and step efficient way to construct aminopyrazoles in good to excellent yields via new C-C/C-N bonds formation utilizing a catalytic amount of NIS in the presence of CHP.(6) A novel efficient protocol for the creation of 6-amino phenanthridine derivatives by Co(acac)2-catalyzed isocyanide insertion with 2-aryl anilines under O2 atmosphere via somophilic radical insertion and homolytic aromatic substitution(HAS) type sp2 C-H functionalization has been developed.(7) Chemoselective synthesis of N3-iminoquinazolinium ylides and pyrazolo[1,5-c]quinazolines via different transition-metalenabled systems has been described. Co(acac)2-catalyzed oxidative isocyanide insertion with hydrazonesn in the presence of TBHP could get N3-iminoquinazolinium ylides in good to excellent yields via new C-N bonds formation. Ni Cl2-catalyzed oxidative isocyanide insertion with hydrazonesn in the presence of Tempo could obtain pyrazolo[1,5-c]quinazolines though four new C-C/C-N bonds formation in a single step.