Electrophilic additions to allenes. VI. The role of steric versus electronic effects in the reactions of arenesulphenyl halides with allenes

Abstract

. Can. J. Chem. 58, 2737Chem. 58, (1980. The role of steric and electronic effects during the rate and product determining steps for the addition of arenesulphenyl chlorides to 1,3-disubstituted allenes has been briefly examined. Both effects appear to be generally of minimal importance during the rate determining step. The available rate data indicate the presence of little, if any, build up of positive charge on sulphur. These results are interpreted in terms of an &2 attack on bivalent sulphur leading to an alkylidenethiiranium ion intermediate. Steric effects are of greater importance in the product determining step, particularly when the sulphenyl chlorides possess two bulky ortho substituents, as in the case of 2,4,6-triisopropylbenzenesulphenyl chloride. Chem. 58,2737Chem. 58, (1980. On a examine brievement le rBle des effets sterique et klectronique dans les &tapes determinant la vitesse de la reaction et la valeur des produits d'addition des chlorures d'arene-sulphenyle sur les alltnes disubstitues en positions 1,3. Les deux effets semblent n'avoir qu'une faible importance sur I'ttape determinant la vitesse de la reaction. Les donnees cinetiques disponibles indiquent la presence d'une faible charge positive sur le soufre. On interprete ces resultats en termes d'une attaque SN2 sur le soufre bivalent conduisant a un ion alkylidenethiiranium intermediaire. Les effets steriques jouent un rBle important dans l'etape determinant la nature des produits formis en particulier quand le chlorure de sulphdnyle possede deux substituants encombrants en position ortho comme dans le cas du chlorure de triisopropyl-2,4,6 benzenesulphCnyle.[Traduit par le journal]In previous papers of this series we have reported the reactions of benzenesulphenyl chloride and some derivatives thereof with a series of 1,3-disubstituted allenes (1-3). In all cases studied the arylthio moiety was observed to attack regiospecifically on the central allenic carbon, with the E isomer formed preferentially or exclusively under conditions of kinetic control. The ratio of products was interpreted as corresponding to the percentage of attack on each face of the respective n systems, and therefore reflecting the direction of approach of the electrophile towards the allenic system. The preponderance of the E isomer led us to propose that one observes steric approach control, wherein the steric interactions in the product determining

Phosphinidine-Palladium Complexes for the Polymerization and Oligomerization of Ethylene

“…Geminal dimethyl groups on the chelate backbone should impart a more restricted conformation to the S-aryl group, possibly leading to more efficient blocking of the axial sites on the metal and potentially higher molecular weight material. The synthesis started with the reaction of tri-isopropylphenylsulfenyl chloride with the potassium enolate of isobutyraldehyde to give the corresponding α-thioaldehyde 12 . The conversion to the cationic palladium complex 14 was carried out as in the case of 11 .…”

“…NMR solvents were vacuum transferred from P 2 O 5 and degassed by repeated freeze−pump−thaw cycles. The following starting materials were made using literature procedures: Mes*PCl 2 , Mes*PH 2 , (cod)PdMeCl, 2,4,6-tri-isopropylthiophenol, α- tert- butylthioacetaldehyde, and 2,4,6-tri-isopropylphenylsulfenyl chloride . NaB(Ar F ) 4 was purchased from Boulder Scientific.…”