PUB - Publikationen an der Universität Bielefeld

The synthesis and spectroscopic characterization of several benzoanellated [5.5.5]-, [5.5.5.6]-, and [5.5.5.5]fenestranes, including the parent difuso-centrotriindan 7, the parent tetrafuso-centrotetraindan 8 (fenestrindan) as well as the tribenzo[5.5.5.6]- and tribenzo[5.5.5.5]fenestranes 27 and 35, are described and discussed in full experimental detail. The highly efficient twofold cyclodehydration of 2,2-dibenzyl-1,3-indandiol 15 and the related spiro-condensed 1,3-indandiols 23 and 29 is the keystep of the synthetic strategy. The new synthetic variant involving the one-pot cyclodehydration/deketalization of the dispiro-ketal diol 29 is particularly convenient. In the case of 7, an alternative Lewis acid-catalyzed double cyclization has been developed. Stereochemical aspects of the 1,3-indandiols and the key tribenzo[5.5.5.6]fenestranes 24 and 25 are discussed in detail.