Studies on the cycloaddition reactions of alkylidene carbenes generated from alkynyl(phenyl)iodonium salts

Abstract

Cycloaddition reactions of alkylidene carbenes generated from alkynyl(phenyl)iodonium triflate were studied. Since alkylidene carbenes from alkynyl(phenyl)iodonium salts can be generated under mild condition, 1-propynyl(phenyl)iodonium triflate 25 was chosen as alkylidene generating reagent. Our approach was the tandem cyclization through the generation of alkylidene carbenes from intermolecular reaction between iodonium salt 25 and nucleophiles which contain the moiety for cyclization. Before the cyclization reaction of alkylidene carbene, it was examined that the reactivity of TMMs generated from alkylidene carbenes. Allyl Meldrum’s acid reacted with iodonium salt 25 to afforded π-π type dimer, but in case of cinnamyl and dimethyl Meldrum’s acid derivatives, the oxygene trapped Meldrum’s acid derivatives were obtained. These results strongly indicated that the reaction of allyl Meldrum’s acid derivatives with iodonium salt 25 proceeded to the TMM through the opening of cyclopropane ring of bicyclo[3.1.0]-1-hexene which was generated from the cyclopropanation of alkylidene carbene. On the basis of dimerization study, cis, anti-fused tricyclopentanoids were synthesized from the reaction of Meldrum’s acid derivatives with iodonium salt 25. As another attempt for the synthesis of tricyclopentanoids, the reaction of three components was investigated. When benzlidene Meldrum’s acid was used as nucleophile precursor for generating alkylidene carbene, the corresponding dimers were not formed. Perhaps, this phenomenon was considered as the narrow reactivity range of iodonium salt 25 with nucleophiles. Unlike the reaction of Meldrum’s acid derivatives with 25, allyl tosylamide afforded azabicyclo[3.1.0] hexanes instead of tricyclopentanoids or dimers via 1,3-diyl trapping reaction. This results probably attributed to less ring strain of 3-azabicyclo[3.1.0]hex-1-ene than that of bicyclo[3.1.0]hex-1-ene. This new methodology can be applied to prepare for azabicyclo[3....