Study On The Cycloadditions Of 2,2-Diester Aziridines With Nitriles Or Triazines

Aziridines are a class of nitrogen-containing three-membered cyclic compounds which are not only present in some organic molecules and natural molecules,but also are key intermediates for preparation of some drug molecules and natural products.They have high activity due to the tension of three-membered cyclic structure.Their derivatives can undergo ring-opening reactions with some compounds.What's more,they can undergo a variety of cycloaddition reactions with compounds bearing diverse unsaturated bonds to synthesize of N-containing heterocyclic compounds such as pyrrolines,imidazoles,oxazolidinones,oxazolidines and other derivatives.Therefore,the research on the cycloaddition of aziridines have becomes a new hot spot and has attracted high attention of researchers.In the first part,AlCl₃-promoted[3+2]cycloaddition of 2,2-diester aziridines via C-C bond cleavages with nitriles for the synthesis of3-imidazolines was reported.The optimal reaction conditions were obtained as follows:0.2 mmol of 2,2-diester aziridine,0.7 mmol of benzonitrile,0.2 mmol of AlCl₃ as a promoter,and 0.5 mL of chlorobenzene as a solvent at 25 ^oC.The product yield can reach 95%.With the established optimal conditions,we next investigated the substrate scope of 2,2-diester aziridines and nitriles.The reaction had a broad substrate scope and most substrates provided good to excellent yields.Then,the reaction mechanism was proposed.The reaction was tested on a gram scale and an excellent yield was obtained.In the second part,TfOH-promoted[3+2]cycloaddition of 2,2-diester aziridines via C-N bond cleavages with nitriles for the synthesis of2-imidazolines was revealed.The optimal reaction conditions were obtained as follows:0.2 mmol of 2,2-diester aziridine,0.4 mmol of benzonitrile,0.2 mmol of TfOH,and 0.5 mL of DCE as a solvent at 45°C.The desired product was provided in 69%yield.With the optimal conditions,we tested the substrate scope of aziridines and nitriles,and most substrates provided moderate to good yields.Then,the reaction mechanism was described.In the next part,cycloadditions of 2,2-diester aziridines with triazines were developed and different multisubstituted imidazoline derivatives were easily obtained.When Yb?OTf?₃ was used as a catalyst,tetra-substituted imidazoline derivatives were obtained.The optimal reaction conditions were as follows:0.2mmol of 2,2-diester aziridine,0.2 mmol of triazine,8 mol%of Yb?OTf?₃ as a catalyst,and 200 mg of 4?MS in DCM?1.0 mL?at 50°C for 2 h.The yield was up to 95%.With the optimal conditions,we examined the substrate scope of aziridines and triazines and most substrates provided moderate to excellent yields.Finally,the reaction mechanism was speculated consulting the literatures.When La?OTf?₃ was used as a catalyst,trisubstituted imidazoline derivatives were obtained.The yield of standard substrate was up to 95%by optimizing the reaction conditions.With the optimal conditions,we investigated the substrate scope of triazines and most substrates provided 51%⁹5%yields.In this paper,the cycloadditions of 2,2-diester aziridines with nitriles or triazines were carried out and different imidazoline derivatives were easily obtained.The products were characterized by ¹H NMR,¹³C NMR and HRMS,etc.and some product structures were further determined by X-ray single crystal diffraction.This paper has the following advantages:1.The catalyst is cheap.2.the reaction conditions are mild,and the experimental operation is simple.3.The product yields are high.