Transition Metal-Catalyzed Carbon-Heteroatom Bond Formation Reactions Starting From Tetraalkylthiuram Disulfides

Benzamides,N,N-dialkylbenzothiazoles,N,N-dialkylthiocarbamates are universal in the core building blocks in medicines,pesticides and materials.Thus it is of great significance to investigate their synthetic methods.This paper mainly explored the C-N bond and C-S bond formation reactions regarding the synthesis of these important compounds strating from tetraalkylthiuram disulfides.The details of the study are as follows:1.By using benzoic acids and tetraalkylthiuram disulfides as starting materials,the copper-catalyzed C-N bond formation reactions to generate N,N-dialkylbenzamides were explored.The type and amount of the catalysts,the type and amount of the oxidants,the solvents,the temperature,the molar ratio of the substrates were screened to obtain the optimal conditions(CuBr as catalyst,DTBP as oxidant,EtOAc as solvent,heating under120? for 10-12 h).Under the optimal conditions,a series of 14 N,N-dialkylbenzamides were furnished in good to excellent yields(74%-95%).All the product structures were identified by necessary spectra.The protocol has the advantages such as easily available raw materials,simple operation,wide substrates computability,broadening the synthetic methods of N,N-dialkylbenzamides.2.By using thioamide as directing group,the palladium-catalyzed ortho C-H activation to generate benzothiazoles(C-S bond formation)was studied.The type and loading amount of the catalysts,base,oxidants were screened,as well as the solvents,temperature and other factors.Under the optimized reaction conditions,a series of 16N,N-dialkylbenzothiazoles were synthesized smoothly in 62%-89%yields,and all the products were identified by necessary spectra.This protocol bears the advantages of avoiding the use of environmentally unfriendly oxidants,efficiency,good substrate suitability,providinganalternativeapproachforthesynthesisof N,N-dialkylbenzothiazoles.3.Copper-catalyzed S-arylation of tetraalkylthiuram disulfides by using diaryliodonium salts was investigated.By screening the reaction parameters,such as type and loading of catalysts,base,solvents,temperature,molar ratio of substrates and other factors,the optimal reaction conditions were as follows:CuI as catalyst,KOt-Bu as base,DMF as solvent,heating at 110?,for 4-6 h.A series of 17 N,N-dialkylthiocarbamates were obtained in good to excellent yields(61%-89%),and all the products were identified by necessary spectra.This method has the advantages of efficiency,good atomic economy,broad substrate scope.Furthermore,two kinds of S-aryl dithiocarbamates were obtained in one step.This method might provide an alternative pathway for the fast preparation of some potentially biologically active compounds.