Photostimulated Reactions of o-Dihalobenzenes with Nucleophiles Derived from the 2-Naphthyl System. Competition between Electron Transfer, Fragmentation, and Ring Closure Reactions

Article abstract of DOI:10.1021/jo00061a040

The photostimulated reaction of o-dihalobenzenes 2 with 2-naphthoxide ions 1-O gave the substitution product on carbon 1 of the naphthyl moiety with retention of halogen (I, Br, and Cl) 3 as well as the ring closure product benzonaphthol<1,2-d>furan (4), with product 3 being an intermediate in the formation of 4.The products obtained in the photostimulated reaction of 2-naphthalenethiolate ions 1-S with 2 depend on the halogens.When both nucleofugal groups are iodine, only the ring closure product benzonaphtho<1,2-d>thiophene (10) is obtained.With o-bromoiodobenzene, the photostimulated reaction gave 10 and the substitution product on sulfur with retention of bromine, while with o-chloroiodobenzene the only observed product was the substitution product on sulfur with retention of chlorine.The photostimulated reaction of 2 with 2-naphthaleneselenolate ions 1-Se gave the same amount of cyclized product benzonaphtho<1,2-d>selenophene (14) and the substitution product on selenium without retention of halogen 15, although in an overall low yield.It is suggested that all these reactions occur by the S_RN1 mechanism.Theoretical studies support the different behavior found with the nucleophiles derived from the 2-naphthyl system.