Reactions of haloarenes, haloheteroarenes and dihalobenzenes with triphenylstannyl anions in DMSO and acetonitrile

We studied different haloarenes, haloheteroarenes and dihalobenzenes with Ph3Sn- ions in DMSO or acetonitrile (CH3CN) as solvents, in the dark or under irradiation to determine whether the halogen metal exchange (HME) reaction or the S(RN)1 process prevails. With p-chloroanisole the photostimulated reaction is sluggish in DMSO. There is an HME reaction with 2- and 3-chlorothiophene. Bromoarenes (p-bromoanisole, p-dibromobenzene and 1-bromonaphthalene) and p-iodoanisole react with Ph3Sn- ions faster by an HME mechanism than by the S(RN)1 process. In the photostimulated reaction of 1-chloronaphthalene, 2-chloro and 3-chloropyridines with Ph3Sn- ions in DMSO, the substitution products are obtained in 72, 82 and 93% yields, respectively. With p-dichlorobenzene the di-substitution product is obtained in 90% yield. All these reactions occur by the S(RN)1 mechanism. Yields improve when the reactions are carried out in DMSO rather than in CH3CN. (C) 1999 Elsevier Science S.A. All rights reserved.