Preparation and Characterization of Alkenyl Aryl Tetrafluoro‐λ⁶‐sulfanes

Abstract

Substituted alkenyl aryl tetrafluoro-λ(6) -sulfanes have been prepared by the direct addition of readily accessible chlorotetrafluorosulfanyl arenes to primary alkynes. Substitution of an apical fluorine of the pentafluorosulfanyl group enables modulation of the reactivity of this little explored functional group while at the same time facilitating the direct investigation of aryl substituent effects on the aryl tetrafluorosulfanyl-substituted products.

Effects of substitution on the reactivity of alkyl aryl tetrafluoro-λ6-sulfanes

“…Complimentary to the previous report [18] where the alkene and alkyne addition partners were substituted by arenes, in this work the limitations of the addition of arene tetrafluoro-l 6 -sulfanyl chlorides to aliphatic alkenes and alkynes are described. The aliphatic substituted addition products were more sensitive toward substituent effects than the aromatic-substituted compounds previously communicated.…”

“…The electron density at C7 increases with the change in hybridization associated with the progressive unsaturation of 3d, 5d, and 10d. Concurrently, increase in electron density of C7 bond resulted in a systematic shortening of the S-C7 bond (1.8148(75) Å to 1.7402(17) Å ), in a manner consistent with diminution of ionic bond character [25] As shown previously a decrease in the C4-S-C7 bond angle and an increase in the S-C7 bond length accompanied the introduction of increasingly election withdrawing substituents to the aryl group of the aryl tetrafluorol 6 -sulfanyl construct [18,24]. The increased significance of an ionic resonance form on the C4-S-C5 bonding and the consequent distortion of geometry around sulfur would be predicted to result in the S-F2 bond exo to the alkane being lengthened relative to S-F4 bond.…”

“…The aliphatic substituted addition products were more sensitive toward substituent effects than the aromatic-substituted compounds previously communicated. The addition of ethereal solutions of chlorotetrafluorosulfanyl arenes 1 to 1-hexyne 2 and 1-hexene 4 [18] was catalyzed by triethylborane [8,9] (Scheme 1), forming 3 and 5, respectively, in as few as 15 min. The addition reactions could also be initiated photochemically, albeit longer reaction times were required.…”

“…Therefore an increase in s could be predicted to result in the chemical shift of C4 moving to lowerfield. However, the 13 The decrease in C7 chemical shift with strongly electronwithdrawing para-substituents was previously observed in the substitution products of aryl alkynes and alkenes [18] and was postulated to be associated with an increase in charge density at C7. This increase in density is consistent with the contribution of ionization of the S-C7 bond predicted by the Rundle-PimentelCoulson [21][22][23]/charge-shift bonding [24] description of bonding at sulfur.…”

“…The preparation and characterization of alkenyl aryl tetrafluoro-l 6 -sulfanes have only been recently reported [18]. The aryl substituents can profoundly influence both the reactivity of the aryl tetrafluoro-l 6 -sulfanyl chloride as well as the stability of the alkyl and alkenyl products formed on addition to alkenes or alkynes, respectively.…”