Halonium-Induced Electrophilic Addition Reactions Of Unsaturated Carbon-Carbon Multiple Bonds

The addition reactions between electrophilic and nucleophilic reagents with unsaturated carbon-carbon multiple bonds belong to important research objectives in organic chemistry. Among them, halonium-induced regio/stereoselective electrophilic addition reactions of alkene, allene and alkyne have garnered extensive attraction. Due to the simultaneous formation of carbon-halogen bond and carbon-heteroatom bond or carbon-carbon bond in a one-pot manner, this metal-free protocol has been developed as a mean for the assembly of haloalkanes, multisubstituted alkenes, heterocycles and carbocycles. It is helpful to explore new reactivity and novel methodology to construct heterocycle and carbocycle by adjusting different type of halonium reagent, carbon-carbon multiple bond and nucleophilic reagent in the electrophilic addition reactions. The thesis consists of two parts as follows:Part I NIS-induced regio/stereoselective electrophilic addition of1H-benzotriazole to alkynes Using1H-benzotriazole as nucleophilic reagent, we explored the electrophilic addition reaction of aromatic alkynes under the promotion of NIS, which resulted in the formation of2-vinyl-2H-benzotriazoles. When H, alkyl or phenyl was attached on the alkyne terminus, only E-adducts were obtained. On the contrary, when bulky trimethylsilyl was attached, Z-adducts were yielded. Part Ⅱ Domino reaction initiated by NBS-induced bromocarbocyclization of enamine estersUsing micahel adduct prepared from tryptamine and methyl propiolate as substrate, we explored the halocarbocyclization induced by NBS. A domino cyclization triggered by bromocarbocyclization has been established to generate tetrohydroazepino[4,5-b]indole derivatives. A mechanism involving ring expansion-rearrangement of aziridine intermediate was proposed.