The Synthesis Of Oxazatricyclic And Spiro Compounds With Azaaromatic Quaternary Ammonium Salts

Azaaromatic quaternary ammonium salts, which can be generated from alkylation of aromatic nitrogen-containing heterocyclic compounds with active alkyl halides, are ionic compounds. Due to the strong electron-withdrawing effect of the nitrogen atom, Azaaromatic quaternary ammonium salts are very reactive compounds. In the presence of a base, aza-aromatic quaternary ammonium salts can be deprotonated to form aromatic nitrogen ylides. These nitrogen ylides have versatile reactivities and can undergo versatile reactions such as Michael addition, nucleophilic addition,1,3-dipolar cycloaddition and so on. They are widely used as important synthons to construct nitrogen-containing heterocyclic compounds in synthetic organic chemistry. In continuation of our objective to establish efficient synthetic methodology for complex polycyclic compounds, herein we wish to synthesis complex polycyclic compounds by using aza-aromatic quaternary ammonium salts as key reactants.1. A series of complex oxazatricyclic systems was efficiently synthesized in satisfactory yields by three-component reaction of isoquinolinium salts, acetone and cyclic 1,3-dicarbonyl compounds in ethanol in the presence of triethylamine as base catalyst. All the products were characterized by IR,1H NMR,13C NMR, HRMS spectroscopy. The single crystal structures of two products were determined by X-ray diffraction method.2. The base catalyzed double-cycloaddition reactions of 4-dimethylamino-l-phenacylpyridinium bromides with 3-phenacylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl-3,3’-bisoxindoles in good yields and with high diastereoselectivity. The similar double-cycloaddition reactions are also carried out. The stereochemistry of dispirocyclopentyl-3,3’-bisoxindoles was discussed on the basis of 1H NMR data and single crystal structures.3. The domino reaction of nitromethane with two molecules of 3-phenacylideneoxindoles in refluxing ethanol in the presence of DBU afforded functionalized dispirocyclopentyl-3,3’-bisoxindoles with two oxindole units at 1,2-positions of the newly formed cyclopentyl ring in good yields and with high diastereoselectivity. All the products were characterized by IR,1H NMR,13C NMR, HRMS spectroscopy. The single crystal structures of three products were determined by X-ray diffraction method.