Alkynyliodonium triflates with enolates

Likewise, the reaction of the lithium enolate of aminomalonate 126 with alkynyliodonium triflates 127 affords alkynylmalonates 128 in good yields (Scheme 52) [111]. The best yields in this reaction are observed when a freshly prepared solution of the lithium enolate in THF is added to a stirred cold solution of the iodonium salt. The use of potassium enolate instead of lithium, or addition of the reagents in a different order, results in lower yields of products 128. 

The bis(alkynyliodonium) triflate 152 reacts with the enolate anions of 15-diketones to afford the respective bis-insertion products 153 (Scheme 60) [122]. 

The reactions of the lithium enolate of diethyl 2-[(diphenylmethylene)amino]malonate with several alkynyliodonium triflates are rare examples of enolate alkynylations with iodonium species other than the ethynyl(phenyl)- and (phenylethynyl)phenyliodonium ions (equation 125)16. Two experimental protocols were followed, i.e. addition of the enolates to the iodonium salts and vice versa, the former procedure giving higher yields of alkynylmalonates. As with other enolate alkynylations, these reactions are thought to involve alkylidenecarbene intermediates. It has been proposed, however, that the carbenes rearrange with migration of the diethyl 2-[(diphenyl) amino] malonate anion 16. 

Alkynyl(phenyl)iodonium salts have found synthetic application for the preparation of various substituted alkynes by the reaction with appropriate nucleophiles, such as enolate anions [980,981], selenide and telluride anions [982-984], dialkylphosphonate anions [985], benzotriazolate anion [986], imidazolate anion [987], N-functionalized amide anions [988-990] and transition metal complexes [991-993]. Scheme 3.291 shows several representative reactions the preparation of Ai-alkynyl carbamates 733 by alkynylation of carbamates 732 using alkynyliodonium triflates 731 [989], synthesis of ynamides 735 by the alkyny-lation/desilylation of tosylanilides 734 using trimethylsilylethynyl(phenyl)iodonium triflate [990] and the preparation of Ir(III) a-acetylide complex 737 by the alkynylation of Vaska s complex 736 [991]. 

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