| Organostibines are organic compounds that contains at least one C–Sb bond.Ac-cording to their valence,organostibines are usually classified as monovalent,bivalent,trivalent and pentavalent organostibines.Trivalent organostibines are the key species to join other valence organostibines,which can be easily converted into other organos-tibines by oxidation and reduction.As an important class of molecules,trivalent o r-ganostibines are widely used to form complexes with transition metals such as Cr,Mo,W,Fe,Ru,Co,Ir and Pt etc.It can also be used as coupling agents in reactions of C–C bond formation.At present,trivalent organostibines are mainly prepared by the rea c-tion of antimony trichloride or tribromide with organolithium reagents or organoma g-nesium reagents.The following problems exist:（1）There is no general synthetic method;（2）Utilization of highly reactive organometallic reagents,which are moisture to air and water,makes it difficult to operate and has a high risk factor;（3）Functional groups are poorly tolerated,for example,halogens（F,Cl,Br and I）,esters,aldehydes,alkenes,and alkynes are not compatible.Although great progress of trivalent organos-tibines has been made in the formation of C-C bond,there are still some shortcomings:（1）The overall efficiency of Csp2-Csp2 bond formation is low.Substrate suitability is poor.It is urgent to develop high efficient catalytic systems of the transformation of organostibines;（2）The synthesis of biphenyl derivatives with similar functional groups has been a great challenge in the field of cross-coupling,and none of the synthetic methods using organostibines as coupling partners can achieve this selec tive conver-sion;（3）The related reports that organostibines were applid in the formation of Csp2-Csp3 bond has not been revealed.In view of the above-mentioned problems of synthesis and transformation of tri-valent organostibines,as well as the properties that halostibines bear organic halides,nickel-catalyzed cross-coupling strategies between organic boron reagents or organic halides and halostibines were proposed.Two different synthetic methods of trivalent organostibines have been developed,which have made groundbreaking progress in re-action efficiency,substrate suitability and functional group tolerance.In view of the shortage of trivalent organostibines in the formation of C-C bond,based on the under-standing of the unique nucleophilic properties of arylated organostibines,palladi-um-catalyzed strategies between organic boron reagents or benzyl halides and ary-latedorganostibines were proposed.And two different methods for construction of C-C bond were developed.Selective oxidative cross-coupling between trivalent organos-tibines and arylboronic acid was achieved,and the application of organostibines was extended to the synthesis of diarylmethane compounds.The main research results of this thesis are as follows:（1）A nickel-catalyzed method for the synthesis of organstibines by Suzu-ki-Miyaura cross-coupling of boronic acids with halostibines was developed.Reactions of aryl boronic acid and alkyl boronic acid with halostibines proceeded smoothly,and63 organostibines were obtained in good yields.The 30 gram-scale synthetic experi-ment demonstrates the practicability of this method.Kinetic results clearly indicate that transmetalation process of organoboronic acids could be a rate-determining step.The separation and characterization of reaction intermediates show that oxidative addition of halostibines to Ni（0） occurred.Based on these experimental results,the possible mechanism involved Ni（0）/Ni（II）was proposed.（2）A highly efficient strategy for the synthesis of organostibines by cross-electrophile coupling of chlorostibines with organic halides was developed.This method is suitable for the cross-coupling of chlorostibines with aryl iodides,aryl bro-mides,aryl chlorides and alkyl iodides,and shows wide substrate scope and good functional group tolerance.Drug derivatives 3cc,3cd and 3ce were afforded in good yields.Natural product derivatives 3cf and 3cg were also obtained in good yields.The successful synthesis of these complex molecules shows that this method has a certain practicability.Compared with nickel-catalyzed cross-coupling of boronic acids with halostibines,this method is more direct and efficient.The kinetic results clearly indi-cate that the possible rate-determining step of the reaction is the reaction process in which chlorotibines participate.The results of control experiments suggest that Ni（II）species formed by the oxidative addition of organic halides to Ni（0）is the key inter-mediates.Based on the above experimental results,the possible reaction mechanisms involved Ni（0）/Ni（II）or Ni（0）/Ni（I）/Ni（III）were proposed.（3）A method for highly selective synthesis of biaryls by palladium-catalyzed cross-coupling reaction of organostibines with arylboronic acids was disclosed.Com-bination Pd Cl2,Selectfluor and Cs2CO3 as catalyst system could effectively solve the problem of selectivity in oxidative cross-coupling.Biaryls with similar functional groups can be synthesized in a highly selective manner.The results of kinetic experi-ments indicate that transmetalation process of arylboronic acids could be a rate-determining step,and the reaction belongs to 2/3 order.The results of stoichio-metric experiments show that the rate of transmetalation between organostibines and Pd（II）is higher than that between arylboronic acid and Pd（II）.Based on these experi-mental results,the possible mechanism involved Pd（0）/Pd（II）was proposed.（4）A method for the synthesis of diarylmethanes via palladium-catalyzed cross-coupling reaction of organostibines with benzyl halides was revealed.The system is suitable not only for benzyl bromides,but also for benzyl chlorides.It is noted that the unique selectivity of alkyl bromides to aryl bromides provides the possibility for the synthesis of functionalized unsymmetric diarylmethanes.The gram-scale synthesis of benzylclofibrate and celecoxib derivative and the recovery of chlorostibine demon-strate the practicability of this method.The possible catalytic mechanism was proposed based on the control experiment. |
