Theoretical Study On The Reaction Of Some Silylenoids And Germylenoids With Aldehydes,Ketones And Dienes

Silylenoids and germylenoids are analogues of carbenoid,they have similar chemical characteristics to carbenoid and are important organic intermediates.An effective and feasible method to obtain cyclopropane compounds is through the reactions of silylenoids,germylenoids with substances which have unsaturated chemical bonds.Due to its active nature,it is still difficult to synthesize and separate them under mild reaction conditions.The research on their reaction is still insufficient,and the reaction mechanism is lack of theoretical support.In this paper,the mechanism of addition reaction between a number of silylenoids and germylenoids with some substances has double bond,such as aldehydes,ketones and dienes,has been studied by quantum chemistry calculations.The main contents are as follows:The addition reaction of silylenoid H₂SiLiClwith formaldehyde are investigated using DFT M062X and QCISD methods.The calculation result indicates that the addition reaction between H₂SiLiCland formaldehyde is divided into two steps,step one is generating ternary ring structure products,followed by generating two five membered ring structure products which are isomers with each other,namely 2,4-dioxasilolane and2,5-dioxasilolane,in which,the path to generate 2,4-dioxasilolane is more prone to happen.The addition reaction of H₂SiLiClwith acetone is studied by the same methods,it is also divided into two steps and there are two competing reaction paths can produce the end products of isomers.On that basis,it explores the mechanism of addition reaction between（SiMe₃）ClSiLiCland phenylacetone by theωB97XD method,finding four possible reaction paths,one of which was the most likely reaction path.The results proofed that the addition reaction between silylenoid H₂SiLiF have two addition reaction modes,that is,1,2-addition reaction and 1,4-addition reaction.In between,there is one transition state on the path of 1,2-addition reaction,and there are two transition states on the path of1,4-addition reaction.The channel of 1,4-addition reaction is more likely to occur.In addition,this paper also studies the addition reaction mechanism of H₂SiLiCland thioacetone.The results indicate that the reaction mechanism resembles that of H₂SiLiClwith acetone.The five-membered ring structure products containing sulfur and silicon atoms can be formed eventually.Germanium is a homologous element of silicon,then theoretically germylenoid has similar reaction characteristics to silylenoid.The DFT M062X and QCISD methods are adopted to study the addition reactions of some germylenoid with formaldehyde,acetone,thioacetone and 1,3-butadiene.According to the reaction results,the mechanisms of the addition reactions of germylenoid are similar to those of silylenoid.