The Study On Nitration Reaction Of Unsaturated Hydrocarbons

Alkenes and alkynes are parts of hydrocarbons, which contain unsaturated carbon-carbon bonds. And their transformations are very important reactions in organic synthesis. Nitroalkenes as the nitration products of alkenes and alkynes are versatile intermediates in synthetic organic chemistry and pharmaceutical. Hence, the preparation of nitroalkenes has always been a very important subject. Although great significants have been achieved in this field, there are still some shotcomings, including harsh reaction conditions, the formation of undesired E/Z isomers, poor substrate scope and poor functional group tolerance, lengthy reaction times. It is still highly desirable to develop environmentally benign, experimentally simple, economical and efficient approaches for the construction of nitroalkenes. In this paper, we studied the direct nitration of alkenes and alkynes, developed a simple, efficient and applicable method.1. The nitrations of alkenes and alkynes with different nitro agents to synthesize nitroalkenes were summarized. And the different methods were compared. On the basis of these, we described the research background and significance.2. The nitration of alkenes was studied. The initial survey of the reaction conditions was performed with styrene as the model substrate and the optimized reaction conditons were determined, styrene 0.5 mmol, NaNO20.75 mmol, K2S2O81.0 mmol, TEMPO 0.6 mmol. ClCH2CH2Cl 2 mL,100℃,24 h. With the optimized reaction conditions in hand, the generalities and limitations of the reaction were explored, mono substituted and multi substituted alkenes were studied. The results showed that a wide range of alkenes including styrenes, aliphatic and heterocyclic alkenes were compatible with this nitration process, affording the desired products in moderate to good yields. And it also has high functional group compatibility. We also found that the products of mono substituted alkenes were E isomer only, while some products of multi substituted were E/Z mixture. And then we chose the stilbene to discuss the stereoselectivity of this method, the nitration process of E-and Z-stilbene were investigated by GC-MS under standard condition, respectively.3. The nitration process of alkynes were explored and the factors affecting the nitration reaction like nitro reagents, oxidant, iodine sources, reaction solvents, temperature and time were investigated. Ultimately the optimal conditions of the protocol were determined, phenylacetylene 0.5 mmol, NaNO22.5 mmol, K2S2O81.0 mmol, I20.25 mmol, ClCH2CH2Cl: H2O (2:1), r.t.,2 h. On the basis of these results, the optimized reaction conditions were further employed to explore the generalities and functional group compatibilities of this reaction. Phenylacetylenes and heteroaromatic compounds underwent the reaction to afford the corresponding nitro alkenes in moderate to good yields. Unfotunately, the aliphatic alkynes failed to provide the desired β-iodonitro alkene products. And phenylacetylenes that contain strong electronic effect groups gave deficien results.4. The mechanism of nitration method of alkenes and alkynes was probed, respectively. According to the results of the control experiments and the reported literatures, the possible reaction mechanism was proposed for these two nitration approaches. Based on the plausible mechanism, partial experimental phenomenon was interpreted, these preliminary verified the rationality of the mechanism.