Electrophilic addition of p-nitrobenzenesulfonyl peroxide to 3,4-dihydro-2H-pyran

Abstract

The addition of p-nitrobenzenesulfonyl peroxide to 3,4-dihydro-2H-pyran (DHP) in alcohols gives high yields of 3-[ [ (p-nitrophenyl)sulfonyl] oxy] -2-alkoxytetrahydropyrans. The stereochemistry of the addition process is dependent on the steric bulk of the attacking alcohol. For small alcohols, trans addition predominates, while bulky alcohols give mostly cis product. The results are compared with analogous haloalkoxylations of DHP.

Bis(arylsulfonyl) Peroxide-Mediated Difunctionalization of Cyclic Enol Ethers

“…30 The nosylate is incapable of engaging in anchimeric assistance, thus the trapping of the cation by a nucleophile results in a diastereomeric mixture. 22 The incorporation of a nosylate at the anomeric position would be a reversible process under the acidic conditions, which is supported by experiments in which NsP and d 4 -AcOH were added in subsequent reaction steps in one pot, which Scheme 2. Carboxylic Acid Scope of Cyclic Enol Ether Difunctionalization a a Reactions were conducted on a 0.2−0.25 mmol scale using the corresponding carboxylic acid as a cosolvent (1 mL).…”

“…We postulate that the nosylation of the enol ether by the peroxide leads to the formation of an oxocarbenium intermediate (Scheme ). The nosylate is incapable of engaging in anchimeric assistance, thus the trapping of the cation by a nucleophile results in a diastereomeric mixture . The incorporation of a nosylate at the anomeric position would be a reversible process under the acidic conditions, which is supported by experiments in which NsP and d 4 -AcOH were added in subsequent reaction steps in one pot, which resulted in the formation of E1 (observed spectroscopically) before substitution to give E2 .…”

“…Bearing the aforementioned reactivity in mind, we sought to leverage this ionic reactivity of bis­(arylsulfonyl) peroxides to perform a 1,2-difunctionalisation (Figure E). Hoffman and co-workers previously demonstrated that 3,4-dihydropyran (DHP) can undergo reaction with NsP; thus, we identified cyclic enol ethers as ideal nucleophile candidates for this reaction, as sulfonylation may be achieved exclusively at the 2-position to generate an oxocarbenium intermediate species that may be intercepted with a nucleophile. The sulfonate may be used as a handle for further modifications (such as nucleophilic displacement, elimination, or deprotection with a thiol).…”