Alkynyl iodonium tosylates, preparation from

Stable esters coming formally from alkynols and carboxylic, sulphonic or dialkyl phosphoric acids were prepared for the first time via alkynyliodonium salts with the corresponding anion. Several alkynyl carboxylates were obtained by anion exchange of alkynyl iodonium tosylates the initially formed salts, PhI+C=CR RCO2, were converted spontaneously into the esters on elution through a chromatographic column packed with an anion-exchange resin (Pol+ArCOj) ... 

Acetylenic ethers and esters represent an important class of functionalized acetylene derivatives of the hypothetical alkynols, RC=COH. The chemistry of acetylenic ethers has been well developed since their first preparation about 100 years ago Several exhaustive reviews covering the literature on acetylenic ethers and their analogs up to 1985 have been published in the last 30 years. In contrast to acetylenic ethers, esters of alkynols were unknown until the mid-1980s when the first preparation of alkynyl tosylates was reported. In the following years a wide variety of alkynyl carboxylate, phosphate and sulfonate esters has been prepared from alkynyl iodonium salts. The chemistry of these novel derivatives of alkynols has been summarized in a recent review. In the last 10 years considerable interest and research activity has arisen toward alkynols themselves and such derivatives as alkynolate salts and silyl ynol ethers. The present chapter will cover the chemistry of acetylenic ethers and esters as well as related derivatives of ynols with emphasis on new developments in this subject during the last 5-10 years. 

Initial methods of preparation of alkynyl(phenyl)iodonium compounds, as the tosylate salts (11), involved the interaction of terminal alkynes with [hydroxy-(tosyloxy)iodo]benzene (10) (equation 3). This method, however, suffers from lack of generality, low product yields, and separation problems from the concomitantly formed vinyl species (12) (equation 3). Recent modifications and improvements in this procedure have resulted in wider applicability and product yields of 60-90% of iodonium tosylates (11). 

The first stable class of alkynyl(aryl)iodonium salts were the tosylates, 9, prepared by the interaction of HTIB (5), with terminal alkynes in refluxing chloroform [Eq. (1)] [11-13]. Unfortunately, this method suffers from lack of generality, separation problems from the concomitantly formed alkene salt, 8, and low product yields of 9. 

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