Abstract
Copper catalysis allows the direct oxygen alkenylation of dialkyl phosphonates with alkenyl(aryl)iodonium salts with selective transfer of the alkenyl group. This novel methodology proceeds with a wide range of phosphonates under mild conditions and gives straightforward access to valuable enol phosphonates in very good yields.
Highlights
Organophosphorus compounds represent an important class of products with a wide range of applications in biology, agriculture and synthetic organic chemistry [1,2,3]
Current methodologies for the synthesis of acyclic mixed enol phosphonates include the Perkow-type reaction between phosphonites and α-halocarbonyl compounds [11], the mercury-catalyzed addition of phosphonic acid monoesters to terminal alkynes [12,13] and multistep procedures involving a Mitsunobu reaction between 2-hydroxyalkyl phenyl selenides and phosphonic acid monoesters followed by an oxidation/elimination step [14] or reaction of an enolate with a phosphonic dichloride and subsequent treatment with an alcohol [15] (Scheme 1a)
We started our studies by investigating the reaction between diethyl phosphonate 1a and styryl(mesityl)iodonium triflate (2a, Table 1)
Summary
Organophosphorus compounds represent an important class of products with a wide range of applications in biology, agriculture and synthetic organic chemistry [1,2,3]. Fañanás-Mastral and Feringa recently reported a catalytic method for the synthesis of mixed alkyl aryl phosphonates based on a copper-catalyzed arylation of phosphonates with diaryliodonium salts [32]. The resulting phosphonium-like intermediate would evolve by Arbuzov-type substitution of one of the alkyl groups, and final reductive elimination would form the new C(sp2)–O bond, providing an acyclic enol phosphonate with concomitant regeneration of the Cu(I) catalyst (Scheme 1b).
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