Cycloadditions Of Aryne And Halopalladation-Annulation Reactions

Arynes as important intermediates have been received considerable attention in organic synthesis. After the excellent precursors were found, benzyne chemistry has won a rapid and sound development, especially in the synthesis of benzo-heterocycle compounds with important biological and powerful pharmacological activities. Halopalladation has been proven to be an extremely important and convenient method for the formation of both carbon-carbon bond and carbon-halide bond in one step, and has been widely studied and applied. This dissertation mainly focus on aryne-promoted ring-expending reaction and cycloaddition of arynes; halopalladation/annulation to synthesize halo-substituted polycyclic aromatic hydrocarbons (PAHs).1. A novel and efficient aryne promoted ring-expanding reaction of aziridinylimines to synthesize 1,4,5,6-tetrahydropyridazine has been developed. In the presence of KF and 18-crown-6, ortho-(trimethylsilyl)-aryl triflates were reacted with N-(1-phenylethylidene)aziridin-l-amine smoothly at 80℃ to provide 1,3-aryl-1,4,5,6-tetrahydropyridazine in moderate to good yields.2. A mild and general [3+2] cycloaddition of arynes with iodonium ylides protocol was discovered for the synthesis of benzofurans. In the presence of CsF, ortho-(trimethylsilyl)aryl triflates were reacted with iodonium ylides smoothly at room temperature to afford benzofurans in moderate to good yields.3. A [3+2] cycloaddition of two carbonyl groups attached diazo compounds with ortho-(trimethylsilyl)aryl triflates was established to furnish indazoles. These substrates underwent an 1,3-dipolar cycloaddition with benzynes, followed by acyl-migration to provide 1,3-diacyl-1H-indazoles. Use of an excess of the aryne precursor afforded N-aryl-1H-indazoles.4. A novel and general halopalladation/decarboxylation/carbon-carbon forming domino protocol was disclosed for the synthesis of 5-halo-6-substituted benzo[b]naphtho[2,1-d]furans. The protocol represents a novel example of trapping the σ-vinylpalladium intermediate, generated from halopalladation of alkynes, by the decarboxylative coupling reaction. This protocol provided an efficient way for the synthesis of nature products and functional materials involving cabon-halide bond formation.5. A halopalladation/annulation protocol has been developed for the synthesis of 5-halo-6-substituted benzo[b]naphtho-[2,1-d]furans. The corresponding products,5-halo-6-substituted benzo[b]-naphtho[2,1-d] thiophenes and 5-chloro-6-phenyl-11H-benzo[a]carbazole, could be obtained in good yields.