The linkage between reversible Friedel–Crafts acyl rearrangements and the Scholl reaction

Friedel–Crafts acyl rearrangements in PPA (at 80–240 °C) and Scholl reactions in AlCl 3 /NaCl (at 140–220 °C) of benzoylnaphthalenes and fluorobenzoylnaphthalenes have been studied experimentally as a function of temperature and time and computationally. 1BzNA , 2BzNA , 1-4FBzNA , 2-4FBzNA , 1-3FBzNA , 2-3FBzNA , 1-2FBzNA , and 2-2FBzNA were synthesized by classical Friedel–Crafts acylations of naphthalene with benzoyl chloride, benzene with 2-naphthoyl chloride, fluorobenzene with 1- and 2-naphthoyl chlorides and of naphthalene with fluorobenzoyl chlorides, and served as substrates in the investigation. Their structures have been determined by X-ray crystallography and verified by their 1 H-, 13 C-, and 19 F-NMR spectra. 1BzNA , 1-4FBzNA , 1-3FBzNA , and 2-2FBzNA crystallized as the E -diastereomers, whereas 2BzAN , 1-2FBzAN , 2-4FBzAN , and 2-3FBzAN crystallized as the Z -diastereomers. The deviations of the carbonyl group from the naphthyl plane were higher as compared with the deviations from the phenyl plane and were considerably higher in the α -naphthyl ketones than in the β -naphthyl ketones. Intermolecular interactions due to C–H···O and/or C–H···F contacts in the crystal structures of 1 E -4FBzNA and 1E1′ E -3FBzAN have been revealed. 1BzNA rearranged in PPA under argon to 2BzNA via deacylation to naphthalene (e.g., 140 °C, 10 h) and underwent a regioselective intramolecular cyclodehydrogenation at high temperatures to the Scholl reaction product 7 H -benz[ de ]anthracen-7-one ( B de AN) (e.g., 200 °C, 6 h). At 80 °C, benzene was isolated. 2BzNA underwent in PPA deacylation to naphthalene (e.g., 160 °C, 6 h) and an intramolecular cyclodehydrogenation to B de AN at high temperatures (e.g., 220 °C, 6 h), necessarily via the putative intermediate 1BzNA . Higher yields of the acyl rearrangement and the Scholl reaction products were obtained under oxygen. 1-4FBzNA and 2-4FBzNA reacted in PPA analogously to 1BzNA and 2BzNA , respectively, with the following exceptions: 2-4FBzNA underwent an acyl rearrangement in PPA to 1-4FBzNA at 260–300 °C, without any formation of the Scholl reaction product 10FB de AN . 1-4FBzNA also did not yield 10FBd e AN . 1-2FBzNA and 2-2FBzNA behaved similarly. The formation of naphthalene and benzene in the deacylation steps indicated cleavages of both the 1- and 2-naphthyl–benzoyl bonds and the 1- and 2-naphthoyl–phenyl bonds to give naphthalene and benzoylium cation and benzene and 1- and 2-naphthoylium cation, respectivel