- Reactions of (Aryloxy)oxosulfonium Ylides with Carbonyl Compounds
-
Reactions of (aryloxy)oxosulfonium salts with alkyllithium followed by the additon of carbonyl compounds gave β-aryloxy sulfones, β-aroyloxy sulfones, and α,β-unsaturated or β,γ-unsaturated sulfones in 1.4-17.9percent, 1.2-7.2percent, and 4.5-13.5percent yields, respectively.Ylides obtained by treatment of these sulfonium salts with n-BuLi reacted with carbonyl compounds to give betaines, which formed unusual four-membered cyclic alkoxyoxosulfonium salts.The aryloxy anions thus formed attacked β-carbons of these salts to afford β-aryloxy sulfones.The aroyloxy anion that might be formed by autoxidation also attacked β-carbons of these salts to afford β-aroyloxy sulfones.When these anions attacked the α- or γ-protones of these salts, unsaturated sulfones were obtained.This is the first example that the reaction of ylide with carbonyl compounds gave sulfone derivatives via four-membered cyclic alkoxyoxosulfonium salts that were produced by the intramolecular SN2 mechanism.The yields of unsaturated sulfones were raised up to 35-60percent by a one-pot reaction.
- Okuma, Kentaro,Nakanishi, Kazuto,Ohta, Hiroshi
-
p. 1402 - 1407
(2007/10/02)
-
- Conversion of Sulfones to Sulfoxides via Hydride Reduction of (Aryloxy)sulfoxonium Salt Intermediates
-
The conversion of sulfones into sulfoxides by a two-stage procedure, involving initial reaction of the sulfone with 4-chlorobenzenediazonium tetrafluoroborate to form an (aryloxy)sulfoxonium salt, R2+S(O)OArBF4-, and subsequent reduction of this with NaBH4*Al2O3, has been investigated.Variations in the nature and amount of the diazonium salt used and its counterion, the temperature of the reaction, and solvent and concentration effects have been investigated in a largely unsuccessful attempt to improve significantly upon the yields in the first stage.It has been found, by using NaBD4, that the hydride reduction of the (aryloxy)sulfoxonium salt in the second stage proceeds mainly by hydride attack at sulfur, rather than by a Pummerer-type mechanism.The latter mechanism, however, does occur when strong base is added to the (aryloxy)sulfoxonium salt prior to hydride reduction.
- Still, Ian W. J.,Ablenas, Fred J.
-
p. 1617 - 1620
(2007/10/02)
-