Polycyclic aromatics, synthesis cyclodehydration

Many polycyclic aromatic compounds have been synthesized by a cyclization reaction known as the Bradsher reaction or aromatic cyclodehydration. This method can be illustrated by the following synthesis of 9-methylphenanthrene ... 

Dibenzofulvene (100), which is a byproduct of fluorenylmethoxycarbonyl (FMOC) deprotection in peptide synthesis, undergoes Michael addition reactions with carbanions. Conversion of 100 with the silyl enol ether of cyclohexanone (101) and a desilylation reagent furnishes directly the ketone 102, that now can be subjected to the already described acid mediated intramolecular cyclodehydration procedure followed by aromatization. The product is again a polycyclic fluoranthene (103), that can be considered as a naphtho annelated fluor-ene in this sequence (see Scheme 50 [150]). 

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See also in sourсe #XX -- [ ]

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