Alkynyliodonium Salts in Organic Synthesis. Dihydrofuran Formation via a Formal Stevens Shift of a Carbon Substituent within a Disubstituted-Carbon Oxonium Ylide

Abstract

The addition of p-toluenesulfinate to the silyl, 1-furanyl, and 1-pyranyl ethers of 1-hydroxybut-3-ynyl(phenyl)iodonium triflate triggers a sequence of reactions that ultimately delivers 2-substituted 3-p-toluenesulfonyldihydrofuran products in variable yields. A putative 1,2-group shift within an unsaturated oxonium ylide (Stevens rearrangement) accounts for the oxygen-to-carbon transfer of the ether substituent. Deuterium labeling studies clarify the mechanistic course of this shift by providing evidence consistent with intramolecular substituent transfer and by identifying the primary source of the proton that intercepts the ylide in the major yield-limiting process.

Organocatalytic Deuteration Induced by the Dynamic Covalent Interaction of Imidazolium Cations with Ketones

“…13 C{H} NMR (75 MHz, CD 2 Cl 2 ) δ 171.5, 69.8, 29.5 (labeled), 22.7, 19.3. Data in agreement with the literature [16] …”

“…The influence of the nature of imidazolium salt on the efficiency of the H/D exchange was also studied. No deuteration was observed in the presence of salts [16][17][18]. The importance of the nature of counterion was also significant: the…”

“…Data in agreement with the literature. [16] Deuterated racemic methyl 2-phenylpropanoate (16-d 1 ). (R)-Methyl 2-phenylpropanoate or racemic methyl 2-phenylpropanoate were used.…”

Manganese(III) Acetate-mediated Oxidative Cyclization of a-Methylstyrene and trans-Stilbene with b-Ketosulfones

“…Dihydrofuran derivatives are known to have other useful pharmacological properties, such as antibacterial [20,21,22], antifungal [20,21] and anticancer activity [23], as well as being valuable potential intermediates in the synthesis of various substances [24]. A wide variety of methods yielding dihydrofurans and cyclopropanes substituted by a sulfonyl group have been developed [25,26,27,28,29]. We report here the reactivity of two alkenes, α-methylstyrene and trans -stilbene, extending previous work on styrene, allylbenzene [30], 1.1-diphenylethylene and derivatives [30,31] and the α,β-ethylenic ketone series [32].…”

Efficient Synthesis of 2,3-Dihydrofurans via the Highly Selective Pd(0)-Catalyzed Coupling-Cyclization Reaction of 3,4-Allenols with Aryl Iodides

“…4 2,3-Dihydrofurans can be prepared from a two-step procedure from g-butyrolactone, 5 base promoted cycloisomerization of 3,4-allenols, 6 and conjugate addition of 3,4-epoxy-2-methylene oxolanes, 7 intramolecular enolate addition to 1alkenyl sulfones, 8 base-mediated nucleophilic cyclization of 5,5-difluoro-4-enols, 9 addition reaction of 1,3-dicarbonyl compounds with alkenes, 10 transition metal-catalyzed coupling-cyclization of a-diazoketones with ethyl vinyl ether, 11 Pd-catalyzed cyclization of silyl-substituted bis(homo)propargylic alcohols, 12 Cr-mediated cycloisomerization of homopropargyl alcohols, 13 and the reaction of p-TolSO 2 Na with 1-hydoxybut-3ynyl(phenyl)iodium triflate derivatives. 14 For all these methods, some of them require lengthy procedure, some need stoichiometric amount of metal complexes. Thus, the development of new and efficient methods for the synthesis of 2,3-dihydrofurans is still catching the attention of synthetic chemists.…”