Intramolecular Cycloaddition Reactions of <i>cis</i>-1,2-Dihydrocatechol Derivatives Incorporating C3-Tethered Diazoketones, Nitrile Oxides, and Azides: Stereocontrolled Routes to Enantiomerically Pure Spiro[5.5]undecanes and Related Systems

A series of enantiomerically pure <i>cis</i>-1,2-dihydrocatechol derivatives incorporating C3-tethered diazoketone, nitrile oxide, or azide residues has been prepared from the precursor iodide <b>7</b> using Negishi cross-coupling reactions. Such derivatives, including diazoketone <b>12</b>, participate in regio- and stereo-selective intramolecular cycloaddition reactions to give adducts, for example, <b>15</b>, that are readily elaborated to spiro[5.5]­undecanes such as <b>18