Synthesis Of N-Fused Heterocycles And Heteroatom-substituted Alkenes Through Gem-Dibromoalkenes

gem-Dibromoalkenes are important synthetic intermediate which can be easily available from aldehydes and CBr4/PPh.3. As an important building block, gem-dibromoalkenes have been used for the synthesis of polysubstituted alkenes,1,3-diynes, carboxamide, carbocycles and heterocycles by metal-catalyzed C-C and C-X (X=N, O, S) coupling reactions. Duing the past three years, I have synthesized a series fused heterocycles including imidazo[2,1-b]thiazols, imidazo[2,1-a] isoquinolines and a series of heteroatom-substituted alkenes. My major work is listed as follow:1. Develop a novel copper-catalyzed aminothiolation of gem-dibromoalkenes with unsubstantiated and substituted2-mercaptoimidazole derivatives by using a catalytic amount of Cul in combination with DMEDA. The procedure is economical and experimentally simple for the facile preparation of fused heterocyclic compounds having two different heteroatom from easily available gem-dibromoalkenes.2. Reactions of thiols and amines with gem-dibromoalkenes in the presence of TBAF-3H2O afford (Z)-2-bromovinyl sulfides and (Z)-2-bromovinyl amines regio-and stereoselectively. The reaction proceeds under catalyst-free conditions with high efficiency. The coupling reactions of the obtained products bearing bromine atoms with phenylacetylene and phenylboronic acid gave trisubstituted alkenes in good to excellent yields.3.(Z)-2-Bromovinyl sulfides and (Z)-2-bromovinyl amines coupled with various N, O, S, and P nucleophiles, selectively giving (Z)-1,2-N,O,1,2-N,S,1,2-S,P,1,2-S,S and l,2-S,O-heterodisubstituted alkenes. In addition, we developed a concise synthetic methodology for the stereoselective synthesis of (Z)-1,2-dithio-l-alkenes. Both symmetric and unsymmetric products have been obtained in very good to excellent yields.4. Pd-catalyzed direct arylation of (Z)-2-bromovinyl amines with substituted aryl iodides and subsequent Pd-catalyzed cyclization via tandem C-H activation lead to a series of benzimidazo [2,1-a] isoquinolines derivatives in moderate to good yield. This method can also be applied to caffeine substrate giving corresponding product in moderate yield.