A Convenient and Scaleable Synthesis of 11,12-Diamino-9,10-dihydro-9,10-ethanoanthracene and Its Enantiomers

A convenient synthesis of 11,12-diamino-9,10-dihydro-9,10-ethanoanthracene (1) is described. A Diels-Alder reaction between fumaryl chloride and anthracene provides an acid chloride. Conversion into an acyl azide followed by a thermal Curtius rearrangement and saponification affords the racemic diamine. Diastereoisomeric salt resolution provides the single enantiomer products, which are used as the chiral backbone of several ligands in asymmetric catalysis, including the Trost asymmetric allylic alkylation ligand 2.