Theoretical Study On The Reaction Mechanism Of The Synthesis Of5,6-dihydropyran-2-ones And Cyclic Ureas Derivatives

In this paper, we summarize the synthesis significance of5,6-Dihydropyran-2-ones andcyclic ureas as well as the research status at home and abroad. We select two theory subjectsfor this, one is the theory study of the reaction mechanism of reactions of cyclopropyl arylketones with ketonic acid to facile preparation of5,6-Dihydropyran-2-ones, the second is thetheory study of reaction mechanism of cycloaddition reaction of2-Vinylaziridines andsulfonyl isocyanates to synthesis of seven-Membered cyclic ureas and five-Membered cyclicureas. we have done the theory study for each of the four synthesis reaction mechanism, inorder to explore the rules of the cyclization reaction of cyclopropane derivatives and aziridinederivatives.The main methods: B3LYP/6-311++G**implemented in Gaussian09package is used tolocate all the stationary points along the reaction pathways. Full optimization and vibrationalanalysis are done for the stationary points on the reaction profile. Zero point energy correctionis included for the energy calculations. In order to explicitly establish the relevant species, theintrinsic reaction coordinate (IRC) is also calculated for all the transition states appearing onthe energy surface profile.According to the four reaction mechanisms of the cyclization reaction of cyclopropanederivatives to synthesis5,6-Dihydropyran-2-ones,we can predict that the reactions have thesimilar mechanism, these reactions have five steps which contains Seven primitive reaction.Reaction (1) is R1and hydrogen ion combined to generate a positive ion intermediate product(INT1) in the acidic conditions that acetic acid (HAc) provides. Reaction (2) contains twoprimitive reaction:(1)INT1and H2O combined to generate a intermediate product (INT2)through the Transition state (TS1).(2) INT2through the Transition state (TS2) to generate aproduct （P1+）through hydrogen transfer. Reaction (3) is （P1+）and (Ac-) further reactionto generate product P1and Acetic acid. Reaction (4) is P1and (R2) through the dehydrationgenerating product (P2) and wather. Reaction (5) also contains two primitive reaction:(1) P2through the transition state(TS4) to generate a product (INT3) through hydrogen transfer.(2)the INT3through the dehydration generating5,6-Dihydropyran-2-ones (P3) and wather(H2O). According to the four synthesis reaction mechanisms of the cycloaddition reaction of2-Vinylaziridines and sulfonyl isocyanates to synthesis of seven-Membered cyclic ureasand five-Membered cyclic ureas. We can predict that the reactions have the similarmechanism, The influence of solvent is very large and the different solvents make the reactionget different product throngh different pathway.when the acetonitrile or THF and so on assolvent,we can get the mixture of seven-Membered cyclic ureas and five-Membered cyclicureas from this cyclization reaction. We can get product seven-Membered cyclic ureas as thesolvent is CH2Cl2. We can get product five-Membered cyclic ureas as the solvent is DMF.When the CH2Cl2as solvent, the cycloaddition reaction between aziridine derivatives(R1)and Sulfonyl Isocyanates(R2) to generate seven-Membered cyclic ureas have two steps.(1) the reactants (R1) generates a five-membered product (P1) though ring expanding reaction.(2) P1and R2generates product seven-Membered cyclic ureas through Transition state(TS2).Decrease the temperature will be good for the reaction.When the DMF as solvent, thecycloaddition reaction between aziridine derivatives (R1)and Sulfonyl Isocyanates(R2) togenerate five-Membered cyclic ureas have only one step: the cycloaddition reactionbetween two reactants R1and R2to generate product five-Membered cyclic ureas (P3). thereaction will be a spontaneous reaction under the condition of atmospheric pressure.