Benzannulated Cycloheptanones from Binaphthyl Platforms
Grégory PietersKamal SbargoudAlexandre BridouxA GaucherSylvain R. A. MarqueFlavien BourdreuxJérôme MarrotDavid FlotGuillaume WantzOlivier J. DautelDamien Prim
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Abstract Preparations of benzannulated cycloheptanones starting from unique binaphthyl molecular platforms are described. Binaphthyl acetic acids proved suitable percursors for fused cycloheptanone architectures. Seven‐membered rings embedded in binaphthyl units were selectively generated by use of Eaton's reagent. Isomeric helical architectures arising from electrophilic cyclisation processes at second reaction sites in the precursors could also be obtained under different acidic conditions. Unambiguous discrimination between isomeric geometries was provided by multiple quantum NMR sequences. DFT calculations were performed and gave evidence of different behaviour of the substrates towards intramolecular electrophilic substitution. The theoretical approach confirmed the experimental results, agreeing completely with X‐ray data.Keywords:
Electrophilic substitution
Abstract The effects of electrophiles and solvents on the stereochemistry of electrophilic substitution of a lithiocarbanion generated from ( S , E )‐1‐phenylbut‐2‐en‐1‐yl diisopropylcarbamate were examined using various acids and carbon electrophiles. The stereochemical outcomes were influenced by the relative ability of the electrophiles and solvents to coordinate to lithium.
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The relative reactivities of selenophen and thiophen in five electrophilic substitutions have been determined by kinetic or competitive procedures. The results have been compared with those available in the literature for furan. In all the reactions examined selenophen exhibits a reactivity intermediate between furan and thiophen.
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Abstract The general synthesis, isolation and characterization of electrophilic iodine reagents of the general formula R 4 N[I(O 2 CAr) 2 ] is reported. These compounds are air‐ and moisture‐stable iodine(I) reagents, which were characterized including X‐ray analysis. They represent conceptually new iodine(I) reagents with anions as stabilizers. These compounds display the expected performance as electrophilic reagents upon interaction with electron‐rich substrates. The performance of these compounds in a total of 47 different reactions of vicinal iodooxygenation of alkenes is studied and some key features on the reagents are revealed.
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A new electrophilic monofluoromethylthiolating reagent N-fluoromethylthiophthalimide PhthSCH2F 1 was developed. Reagent 1 could be readily synthesized from easily available starting materials benzyl mercaptan and CH2FCl in three steps. N-fluoromethylthiophthalimide 1 is a powerful electrophilic monofluoromethylthiolating reagent that allows the monofluorome-thylthiolation of a wide range of nucleophiles including alkynes, aryl/vinyl boronic acids, electron-rich heteroarenes,-ketoesters and oxindoles, as well as thiols under mild conditions.
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A comparative study between a relative experimental scale of electrophilicity and a theoretical absolute scale based on electronic reactivity indexes is presented. The theoretical scale correctly predicts the experimental electrophilicity within the dihalogen and inter-halogen subseries (XY) including F2, Cl2, Br2, BrCl, and ClF and the HX (X = F, Cl, Br) series. It is shown that the best correlation is obtained for the local electrophilic index that encompasses the global electrophilicity power weighted by a local factor described by the electrophilic Fukui function. This result is in agreement with the electrostatic model of Legon (Angew. Chem., Int. Ed. Engl. 1999, 38, 2686), as the electrophilic power of molecules is mainly determined by the local properties of the electrophilic ends of HX and XY species. We also evaluated the electrophilicity of Li2, LiH, LiF, and LiCl species for which experimental data are not available. Whereas LiH is predicted to have an electrophilic potential comparable to that shown by the dihalogen and inter-halogen series but higher than that of the HX species, LiF and LiCl are predicted to display an electrophilic pattern even higher that those of the XY and HX molecules. On the other hand, Li2 displays an electrophilic pattern even lower than that of F2.
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