Oxidation of congested thiophene 1,1-dioxides with m-chloroperbenzoic acid. Formation of epoxides vs. ring-contracted thiete 1,1-dioxides

Direct synthesis of highly strained bifunctionalized 2H-thiete 1,1-dioxides

“…The m CPBA oxidative ring contraction of congested 3,4-di( tert -butyl/(adamantan-1-yl)thiophene 1,1-dioxides is an alternative method in construction of monofunctionalized 2-acyl-2 H -thiete 1,1-dioxides, but with limited examples (Scheme 1d). 9…”

“…Functionalized 2 H -thiete 1,1-dioxides are important pharmaceutical cores, 10 such as tubulin-polymerization inhibitors. 9 Our research group focuses on the synthesis and stereochemistry of four-membered heterocycles, especially via [2 + 2] annulations of imines with ketenes, 11 sulfenes, 12 and phosphenes. 13 The [2 + 2] annulations of sulfenes generated from sulfonyl chlorides with electron-rich alkenes (ketene N,N -, N,O -, and O,O -acetals, vinyl ethers, and enamines) and alkynamines have been well investigated.…”

“…The mCPBA oxidative ring contraction of congested 3,4-di(tert-butyl/(adamantan-1-yl)thiophene 1,1-dioxides is an alternative method in construction of monofunctionalized 2-acyl-2H-thiete 1,1-dioxides, but with limited examples (Scheme 1d). 9 Because of limited synthetic strategies, decoration of simple 2H-thiete 1,1-dioxides became a choice to construct new 2H-thiete 1,1-dioxide derivatives recently. 2H-Thiete 1,1dioxides were modified via the Pd-catalyzed α-arylation/styryla-tion/acylation and via α-metalation followed by reactions with several electrophiles.…”

An Investigation of the Reactivity of MCPBA and α-Bromoalkenes under ­Traditional or Microwave-Assisted Conditions: Selective Formation of ­Epoxides or Allylic Bromides

“…1 Since Prilezahev's discovery in 1908, 2 the reaction of alkenes with m-chloroperbenzoic acid (MCPBA) was constantly reported in the literature as the basic synthetic method for epoxide formation, 3 but only few examples appeared using peracids with more complex substrates, such as 2-alkenyl-2-halo-esters or amides. 4 On the other hand, an interesting study by Kocienski 5 on the 1,3-rearrangement of allylic sulphones caused by MCPBA in the presence of aqueous sodium hydrogen carbonate, 6 has been reported in the literature. The author proposed for this reaction a radical-chain mechanism.…”

“…In aqueous biphasic media, the reactivity of peracid is slightly diminished, however, the system is still sufficiently reactive and a mixture of 2 and 3 in approximate equal proportion, as estimated by 1 H NMR, was obtained. Finally, in the presence of aqueous sodium bicarbonate, a procedure described for the preparation of acid sensitive epoxide, 6 the exclusive rearrangement of bromide was obtained, due to the lower rate of the epoxidation, that is known to be enhanced by acid catalysts. The results observed in the reaction with hydroquinone, which is known to capture radicals, strengthen the hypothesis on a radical mechanism for the bromine 1,3-shift, with respect to a possible S N 2 mechanism from a transient bromide ion.…”