PUB - Publikationen an der Universität Bielefeld

The construction of the polycyclic frameworks of phenanthro-annelated all-cis-[5.5.6.6]fenestrane, cis,cis,trans,cis-[5.5.6.6]fenestrane, and a related broken [6.5.6]fenestrane is reported for the first time. On the basis of our established synthesis of benzoannelated fenestrindanes, spirocyclic di(9-phenanthryl)methyl-1,3-indanediols were prepared with complete stereocontrol and subjected to cyclodehydration. Surprisingly, the 9-phenanthrylmethyl residues underwent preferential peri attack, rather than ortho attack, to generate 1,10-phenanthro rather than 9,10-phenanthro units. In this way, the cyclodehydration of 2,2-di(9-phenanthryl)methyl-1,3-indanediol gives rise to two new six-membered rings with the [6.5.6]fenestrane skeleton. The cyclodehydration of the related trans- and cis-diphenanthryl spiro(cyclohexane-1,2-indanediols) generated one new five- and one new six-membered ring stereospecifically to afford the respective all-cis- and cis,cis,trans,cis-benzodiphenanthro[5.5.6.6]fenestranes in good yields. The crucial constitutional and stereochemical features of the new fenestranes were determined by single-crystal X-ray structure analysis and variable-temperature (VT) NMR spectroscopy.