Sequential and regioselective Friedel–Crafts reactions of gem-dihalogenocyclopropanecarbonyl chlorides with benzenes for the synthesis of 4-aryl-1-naphthol derivatives

Abstract

Novel, sequential and regioselective Friedel–Crafts type reactions of (E)-3-aryl-2,2-dihalogenocyclopropanecarbonyl chlorides 1 and 2,2-dichlorocyclopropanecarbonyl chlorides 3 with benzenes produce various 4-aryl-3-halogeno-1-naphthols 2 and 4-aryl-1-naphthols 4, respectively. One of the benzannulations involves the intramolecular cyclization of acid chlorides 1, followed by intermolecular coupling with substituted benzenes to give 4-aryl-3-halogeno-1-naphthols 2. As a demonstration of this annulation, 4-aryl-3-bromo-1-naphthols 2i and 2k are successfully converted into new analogues of 1-aryl-3-hydroxymethyl-4-methoxy-2-naphthoic acid lactones 13, a class of lignan lactones. The other benzannulation involves three series of reactions using acid chlorides 3a–c: (1) the intermolecular Friedel–Crafts acylation of 3 with one benzene molecule giving the intermediary 2,2-dichlorocyclopropyl(phenyl)methanones 14a–c; (2) the intermolecular trapping of 14a–c with another benzene molecule accompanied by regioselective ring opening; and (3) the final intramolecular cyclization giving 4-phenyl-1-naphthols 4a–c. The use of p-xylene also gives the corresponding 4-(p-xylyl)-1-naphthol 4d. The reactions of alternatively prepared ketones 14 with benzenes gives a variety of ‘unsymmetrically’ substituted 4-aryl-1-naphthols 4c,e–k under identical conditions. However, the reaction using p-methoxyphenyl ketone analogues 14g does not produce 4-aryl-1-naphthols, but gives 5-aryl-2-(p-methoxyphenyl)-3-methylfurans 16. These annulations proceed straightforwardly (in a one-pot manner) and this variation is due to the highly regioselective cyclopropane ring-openings.