Studies On The C-H Bond Cyanation, Alkoxycarbonylation And Sulfonation Reactions

Transition metal catalyzed reaction is one of the most effective methods to form C-C and C-X bonds. In recent years, functionalization of C-H bonds has emerged as one of the most hotspots in synthetic chemistry which meets the requirements of atom economy and exhibits excellent regioselectivity and reactivity. Based on our previous works, we have demonstrated the ruthenium-catalyzed C-H di-t-butoxycarbonylation of arenes using di-t-butyl dicarbonate as the esterification reagent. Besides, we have developed C-H cyanation and sulfonation reactions using isocyanides as the cyanide source or ligand. The results are listed as follows: 1. Ruthenium-Catalyzed Di-t-butoxycarbonylation of ArenesThe reports on ruthenium catalyzed C–H bond alkoxycarbonylation reactions are very limited. In this part, we have developed the ruthenium-catalyzed direct double C-H bond alkoxycarbonylation of arylpyrimidines and aldimines utilizing commercial available di-tert-butyl dicarbonate as efficient esterification reagent. To our knowledge, the given approach features the first example that utilizes commercial available di-tert-butyl dicarbonate as the esterification reagent in C–H bond activation reactions. This method provides an unique access to tertiary dicarboxylated products, which could be converted to medicinally valuable 3-hydroxyphthalide and isoindolinone derivatives easily. Furthermore, ortho-carboxylate aldimine could undergo smooth t-butoxycarbonylation reaction and produce the nonsymmetrical di-ester efficiently. 2. Rhodium-Catalyzed Direct C–H Bond Cyanation of Arenes with IsocyanideIn this chapter, we have developed a rhodium-catalyzed C–H bond cyanation of(hetero)arylpyrimidines using tert-butyl isocyanide as an efficient “CN” source with good regioselectivity and functional group tolerance. The present rhodium catalyst system was also successfully applied to the direct C–H cyanation of olefinic double bonds leading to cycloalkenyl nitriles in good yields. Furthermore, mechanistic studies indicated that the addition of tertiary isocyanides(e.g. AdNC and t-BuNC) might be crucial to give cyanation products through β–alkyl elimination. 3. Isocyanides Induced Activation of Copper Sulfate: Direct Access to Heteroarene Sulfonate EstersNormally, multiple steps, harsh conditions or specific reagents are required for the preperation of sulfonate esters. In this part, we have successfully revealed a direct synthesis of heteroaryl sulfonate esters by reaction of electron-rich heterocycles(indoles, aza-indoles, pyrroles, pyrazoles and carbazoles) with stable copper sulfate, alkyl halides or aryl iodonium salts. Copper sulfate was first used as a cheap and readily available sulfonation reagent, which has been activated by isocyanides. The given approach provides an efficient access to alkyl and aryl heteroaryl sulfonates with operational simplicity and a wide substrate scope.