Efficient Preparation of Polysubstituted Naphthyl Phenyl and Dinaphthyl Ketones from Naphthalenic Esters by Anionic Homo-Fries Rearrangement

Abstract

The anionic homo-Fries rearrangement of naphthalenic esters can be effected in good yield to provide regiocontrolled access to complex diaryl ketones.

Key words

Homo-Fries rearrangement - naphthyl phenyl ketone - dinaphthyl ketone - xanthone

References

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• 7c

  For the preparation of the naphthalenic precursors, see ref. [3]

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8

Anionic Homo-Fries Reaction of Ester 5a: A solution of ester 5a (269 mg, 0.397 mmol) in THF (1.59 mL, from which residual water had been eliminated with n-BuLi and o-phenanthroline) under argon was cooled to -55 to -45 °C and treated dropwise with n-BuLi (0.203 mL, 0.437 mmol). After being stirred for 2 h at this temperature, the reaction mixture was treated with sat. aq NH₄Cl solution, allowed to warm to 20 °C, and diluted with EtOAc. The crude product was isolated with EtOAc in the usual manner and purified by radial thin-layer chromatography (hexane in EtOAc, 9:1 to 1:1) to give 43 mg (16%) of recovered starting material, 32 mg (13%) of debrominated starting material, and 130 mg (55%, 65% brsm) of dinaphthyl ketone 6a as a white solid. Ketone 6a: Mp 220-224 °C (cyclohexane-dichloromethane); IR(neat): 3454, 1619, 1573 cm^-1; ¹H NMR (200 MHz, CDCl₃): δ = 3.41 (s, 3 H), 3.57 (s, 3 H), 3.83 (s, 3 H), 3.87 (s, 3 H), 3.90 (s, 6 H), 4.55 (d, J = 6.8 Hz, 2 H), 5.03 (s, 2 H), 6.37 (d, J = 2.4 Hz, 1 H), 6.45 (d, J = 2.4 Hz, 1 H), 6.60 (d, J = 2.1 Hz, 1 H), 6.70 (d, J = 2.1 Hz, 1 H), 6.87 (s, 1 H), 7.05-7.35 (m, 5 H), 7.41 (s, 1 H); ¹³C NMR (75.4 MHz, CDCl₃): δ = 55.3 (CH₃), 55.4 (CH₃), 56.0 (CH₃), 63.9 (CH₃), 64.0 (CH₃), 64.1 (CH₃), 64.7 (CH₂), 70.2 (CH₂), 97.4 (CH), 98.7 (CH), 99.3 (CH), 103.2 (CH), 111.1 (C), 114.7 (C), 124.4 (CH), 125.4 (C), 127.4 (2 CH), 127.8 (CH), 128.3 (2 CH), 131.3 (C), 136.3 (C), 139.3 (C), 139.5 (C), 155.1 (C), 156.0 (C), 157.6 (C), 157.8 (C), 159.4 (C), 159.6 (C), 198.6 (C); MS (DCI): m/z (%) = 599 (50) [MH⁺], 279 (100); Anal. Calcd for C₃₅H₃₄O₉: Mr, 598.2203. Found: Mr (mass spectrum, EI), 598.2211.