Studies On The Synthetic Reactions Of Nitrogen-Containing Heterocycles Involiving Ketenimines

The heterocyclic compounds is the largest class of organic compounds. Given its unique structure and properties, they play an important role in many areas. As one of the most important heterocyclic compounds, nitrogen-containing heterocyclic compounds are widely used in biology, pharmaceutical chemistry and material. Synthesis of nitrogen-containing heterocyclic compounds has been a hot research field of organic synthetic chemistry. Development of simple, safe and efficient methods for the synthesis of new nitrogen-containing heterocyclic compounds is the mission of synthetic organic chemists. Based on the summary of reported synthetic methods of ketenimines and their utilizations in building heterocyclic compounds, three new methods were developed for the synthesis of nitrogen-containing heterocyclic compounds on the basis of ketenimines. The details are summarized as following:1. A novel Cu-catalyzed fourcomponent reaction of imidoly chlorides, sulfonyl azides, and two terminal alkynes was developed, which afforded polyfunctionalized azetidin-2-imines in good to excellent yield with high diastereoselectivity. Startingmaterials are easily accessible. This one-pot reaction proceeded smoothly at room temperature with easy operation. It occurred in a parallel catalysis manner, including a copper catalyzed Csp-Csp2coupling, a copper-catalyzed alkyne azide cycloaddition, and a [2+2] cycloaddition. All of these separate reactions represent the frontier of modern organic chemistry and fit the basic requirements of green chemistry with high atom economy. Moreover, the synthesized azetidin-2-imines could be conveniently converted into the structurally interesting dihydroazeto[1,2-a]benzo[e]azepin-2(4H)-immes.2. A concise and efficient method for the synthesis of polyfunctionalized pyrazoles and pyrimidine-imides was developed based on the CuAAC with the participation of4-substituted-1,3-butadiyne. Two key intermediates, β-alkynylketenimine and allenyl-imine, were included in this transformation and both of them were high nucleophilicity. Using hydrazides as1,2-dinucleophile, the β-alkynylketenimine and allenyl-imine intermediates were captured successively and a series of polyfunctionalized pyrazoles was successfully synthesized in high yields with good regioselectivity. Furthermore, we extended the application of this method to the synthesis of six-membered rings. Using amidine as1,3-dinucleophile, a series of pyrimidine-imides was synthesis in high yields with good regioselectivity. This methodology is concise, general, efficient, and atom-economic and could have a bright future in organic synthesis.3. Tandem reactions for the synthesis of benzo[b]carbazoles, benzo[b]benzo[5,6]indolo[3,2-h]carbazoles, fluoreno[9,1-ab]carbazoles, and fluoreno[9,1-ab]fluoreno[1’,9’:5,6,7]indolo[3,2-h]carbazoles have been developed. The one-pot reaction involved a tandem Wolff rearrangement/aza-Wittig reaction/biradical cyclization/1,5-H shift process. A variety of substrates were suitable for this reaction. The products have been demonstrated to emit lights at a range of410-521nm with quantum yields up to62%in dichloromethane solution. It is believed that the synthesized compounds might be fabricated in optoelectronics devices for material science study or applied as new fluorophores in the development of new fluorescent chemosensors in life science.4. From the thought of stabilizing1-copper-1,2,3-triazole intermediates through intramolecular coordination, a concise and efficient method for the synthesis of3-diazoindolinimines was developed from o-alkynylanilines and sulfonyl azides based on CuAAC. The reaction proceeded smoothly at room temperature with easy operation. Although the expected triazoloindoles were not obtained, we speculated that the final products3-diazoindolinimines were transformed from triazoloindoles through ring-chain isomerizations. Furthermore, the obtained3-diazoindolinimines could be utilized as a-imino carbene precursors for the constraction of a range of valuable indole molecules including pyrrolo[2,3-b]indoles, spirocyclopropyl iminoindoles,2,3-dihydropyrrolo[2,3-b]indoles,3,3’-biindoles, and2,3’-biindoles.