Intramolecular Friedel-Crafts Acylation Versus Intramolecular Transacetalization – a Novel Approach Towards the Synthesis of Substituted Naphthalene Derivatives

A novel approach towards the synthesis of substituted naphthalene derivatives is accomplished. 2- Tosylnaphthalenes were prepared by treatment of 4-aryl-4- hydroxy-3-tosylbutanal ethylene acetals (10a-e) with a catalytic amount of p-toluenesulfonic acid under reflux via an intermolecular Friedel-Crafts acylation. A meta-alkoxy substitution on the 4-arylring promoted the formation of2- tosylnaphthalene derivatives over the furan formation. Analogously, treatment off I-benzyl-l-(4-benzyloxy-3- methoxyphenyl)-3-(1, 3-dioxan-2-yl) propanol (18a) under the same reaction condition afforded 5-benzyl-2-benzyloxy-3- methoxynaphthalene (19 ). The X-ray single crystal structures of 6-hydroxy-7-methoxy-2- tosylnaphthalene (13) were determined to ascertain the substituted naphthalene product from the ring closure