Site-Specific Preparation of 3-Fluoro-1-substituted-naphthalenes via a Novel Base-Catalyzed Cyclization Reaction from (E)-Monofluoroenynes

Abstract

A novel cyclization reaction for the preparation of 3-fluoro-1-substituted-naphthalenes is reported. (E)-Monofluoroenynes, which are prepared by Sonogashira coupling reaction from (Z)-1-bromo-1-fluoroalkenes, undergo cyclization to afford 3-fluoro-1-substituted-naphthalenes in good to excellent yields when treated with DABCO or DBU in refluxing N-methyl-2-pyrrolidinone (NMP). [reaction: see text]

Site-specific preparation of 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes via base-catalyzed cyclization of enyne derivatives

“…Similar to the mechanism proposed in our previous reports [20][21][22][23], the reaction pathway is illustrated in Scheme 2. First, the base catalyzes the isomerization of the enyne to the allene intermediate, which undergoes 6p cycloaddition to form the two-ring system.…”

“…Barton and coworkers reported fluorination of benzofurans with trifluorofluorooxymethane (CF 3 OF) to give CF 3 O and F adducts [19]. Recently, we have developed a novel base-catalyzed cyclization to site-specifically prepare substituted naphthalenes and polycyclic aromatic hydrocarbons [20][21][22][23]. Herein, we wish to report the utilization of this base-catalyzed cyclization for the site-specific preparation of substituted heterocyclic compounds, such as benzo [b]furans and benzo[b]thiophenes.…”

1,3-Dien-5-ynes: Versatile Building Blocks for the Synthesis of Carbo- and Heterocycles

“…1). 75,76,77 He has also extended this methodology to the synthesis of phenanthrenes by cycloaromatization of o-(alkynyl)biphenyls 77 (Scheme 13, eq. 2) and of benzo [b]furanes and benzo [b]thiophenes from 1-heteroaryl-1-en-3-ynes (Scheme 13, eq.…”

Development and applications of highly selective palladium-catalyzed monocoupling reactions of (cyclo)alkenes and 1,3-alkadienes bearing two or three electrophilic sites and bis(enol triflates) with terminal alkynes

“…An example of a chemoselective and stereospecific Sonogashira monoalkynylation reaction of a stereodefined 1-fluoro-1-iodo-1-alkene was described in 2006 by Burton and coworkers. 205 They prepared (E)-1,2-difluoro-1-iodo-2phenylethene (409) in 83% yield by the reaction of (Z)-1,2difluorostyrene (408) with n-BuLi in THF/Et 2 O at -100 °C for 0.5 h followed by the addition of a THF solution of iodine. Compound 409 was subsequently reacted with 1.5 equiv of 1-dodecyne, 4 mol% PdCl 2 (PPh 3 ) 2 and 0.25 mol% CuI in Et 3 N at room temperature to give (Z)-1,2-difluoro-1phenyl-1-tetradecen-3-yne (410) in 73% yield.…”