49714-67-2Relevant articles and documents
Remarkably Facile Solvolyses of Triflates via Carbocationic Processes in Dimethyl Sulfoxide
Creary, Xavier,Burtch, Elizabeth A.
, p. 1227 - 1234 (2007/10/03)
A number of triflates have been shown to undergo clean pseudo-first-order solvolysis reactions in DMSO-d6 to give products derived from carbocationic intermediates. Thus, t-BuCH(OTf)CO-t-Bu (5) and t-BuCH 2OTf (9) react readily in DMSO-d6 at 25 °C to give a rearranged oxosulfonium salts, and subsequent alkene products where methyl migration to the incipient cationic center occurs. t-BuCH(OTf)CO 2CH3 (14) gives analogous rearranged products, and 1-methylcyclopropyl triflate (21) gives a ring-opened allylic oxosulfonium salt. These triflates react primarily via kΔ pathways. 6-Methylbicyclo[3.1.0]hex-6-yl triflate (23), bicyclo[2.2.1hept-1-yl triflate (24), 1,6-methano[10]-annulen-11-yl triflate (25), (CH3) 2C(OTf)CO2CH3 (26), and (CH3) 2CCN(OTf) (29) all react in DMSO-d6 to give carbocation-derived products. PhCH(OTf)CF3 (33) and substituted analogues also react readily in DMSO-d6, and the Hammett ρ + value is -3.7. This suggests a "borderline" mechanism where the transition state has substantial charge development. The primary feature of these solvolyses is the high reactivity of all of these triflates in DMSO-d6. Thus, these triflates are all more reactive in DMSO-d 6 than in HOAc, and for most, rates are faster than in CF 3CH2OH. Triflates 5, 21, 29, and 33 are 10 8-109 times more reactive in DMSO-d6 than the corresponding mesylates. It is suggested that the decreased need for electrophilic solvation of trifiate anion, and the high cation solvating ability of DMSO, are the reasons for the high triflate reactivity in DMSO-d 6.
