Tosylates alkynyl iodonium

An interesting reaction between the bis phenyl iodonium triflate of acetylene and the silyl enol ether of acetophenone afforded an allene (PhCOCH=C=C=CHCOPh, 84%) [6], Also, alkynyl iodonium tosylates and carbon monoxide in methanol or ethanol, with palladium catalysis, furnished alkyne carboxylates [53]. 

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) ... 

Sodium azide with alkynyl iodonium tosylates at — 70°C afforded an unstable ylide which in the presence of triethylsilane was transformed to different products, depending on the solvent [58] ... 

Alkynyl(phenyl)iodonium Tosylates Preparation and Stereospecific Coupling with Vinylcopper Reagents. Formation of Conjugated Enynes P. J. Stang and T. Kitamura, Department of Chemistry University of Utah, Salt Lake City, UT 84112... 

Recent examples of the rearrangement or alkynylation pathway include conversions of arylethynyl- and er -butylethynyl(phenyl)iodonium tosylates 24 and 25 to alkynylphosphonates, -selenides, and -tellurides with the appropriate anion salts in DMF (Scheme 50) [145-147], and a similar synthesis of push-pull selenides and tellurides from alkynyliodonium triflates containing electron-withdrawing groups in the alkynyl moiety [148]. 

An alternative approach for alkynyl carboxylates involved reaction between [bis(acyloxy)iodo]benzenes and lithium acetylides [59]. Alkynyl iodonium salts afforded with sodium carboxylates in the presence of water 1-acyloxyketones heating in an excess of acetic acid gave similarly a-acetoxy ketones [60], Alkynyl tosylates and mesylates were obtained from the thermal decomposition of isolable alkynyl iodonium sulphonates. 

The conversion of terminal alkynes to alkynyl (phenyl) iodonium tosylates with HTIB, considered here as an instructive example, is best understood as a polar process initiated by electrophilic attack of HTIB on the triple bond of the alkyne (equation 5)46. Loss of H2Q... 

The synthesis of the first alkynyliodonium tosylates was achieved by the treatment of terminal alkynes with [hydroxy(tosyloxy)iodo]benzene (HTIB) (equation 8)8,10,11. Such reactions are generally conducted with an excess of alkyne in chloroform at reflux, although they can be carried out at room temperature, and dichloromethane can be employed as solvent. This procedure is, however, restricted to terminal alkynes in which R is either an aryl group or a bulky alkyl group. With linear alkyl groups (i.e. R = n-Pr, n-Bu, fl-C5Hn), phenyl(/ -tosyloxyvinyl)iodonium tosylates are obtained instead (equation 9)8. In some cases (R = /-Pr, /-Bu), mixtures of alkynyl- and (/ -tosyloxyvinyl)iodonium tosylates are produced8. ter -Butylacetylene appears to be the optimum substrate for this approach and has been employed with a series of [hydroxy(tosyloxy)iodo]arenes for the synthesis of various aryl(ter/-butylethynyl)iodonium tosylates (equation 10)9. 

The presence of catalytic amounts of cuprous triflate or silver(I) sulfonates exerts a remarkable influence on the activation energy and regiochemistry of alkynyl(phenyl)-iodonium tosylate and mesylate decompositions5,6. Such reactions proceed in acetonitrile at room temperature and afford moderate yields of alkynyl tosylates and mesylates (equations 82 and 83)5,6. It is noteworthy, however, that the treatment of alkynyliodonium triflates (R = n-Bu, r-Bu) with cuprous triflate in acetonitrile does not afford alkynyl triflates6. Silver(I) catalysis has similarly been applied to the conversion of bis(alkynyliodo-nium) tosylates to bisalkynyl tosylates (equation 84)43. As might be expected, mono-tosylate esters are also produced in these reactions. 

ALKYNYL(PHENYL)IODONIUM TOSYLATES PREPARATION AND STEREOSPECIFIC COUPLING WITH VINYLCOPPER REAGENTS. FORMATION OF CONJUGATED ENYNES. 

Alkynyl(phenyl)iodonium sulfonates are stable, microcrystalline substances that can be stored and used indefiniteiy with little or no decomposition. They have been employed in the formation of aryl (2-furyl)iodonium tosylates, alkynyl sulfonate, carboxylate and phosphate esters, tricoordinate vinyliodinane species,fO and alkylidenecarbene-iodonium ylides. <... 

ALKYNYL(PHENYL)IODONIUM TOSYLATES PREPARATION AND STEREOSPECIFIC COUPLING WITH VINYLCOPPER REAGENTS. FORMATION OF CONJUGATED ENYNES. I-HEXYNYL(PHENYL)-IODONIUM TOSYLATE AND (E)-5-PHENYLDODEC-5-EN-7-YNE... 

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. 

The first successful preparation of acetylenic esters involved the use of alkynyl (phenyl)iodonium salts 97-99, which are now readily available by a variety of methods. The first reported members of acetylenic esters, alkynyl sulfonates 94, have been prepared by treatment of alkynyl(phenyl)iodonium tosylates or mesylates (97) with catalytic CuOTf or AgOTf in dry acetonitrile (equation 63) . ... 

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). 

Single-crystal X-ray structural data have been reported for the following alkynyliodonium compounds the parent ethynyl(phenyl)iodonium triflate (368) [495], phenylethynyl(phenyl)iodonium tosylate (369) [477], cyanoethynyl(phenyl)iodonium triflate (370) [458], propynyl(phenyl)iodonium periodate (371) [502], trimethylsilylethynyl(phenyl)iodonium triflate (372) [503], 3,3,3-trifluoropropynyl(phenyl)iodonium triflate (373) [504], bis(alkynyl)iodonium triflate 374 [505] and complexes of ethynyl(phenyl)iodonium [506] and l-decynyl(phenyl)iodonium [507] tetrafluoroborates with 18-crown-6 (Figure 2.13). 

The reaction of HTIB with alkynes generally affords two products alkynyl- (175) and alkenyl-(phenyl)iodonium (176) tosylates (Scheme 3.75) [234-238], Alkynyl(phenyl)iodonium tosylates 175 are major products in the reactions of terminal alkynes bearing bulky substituents (R = fcrf-butyl, scc-butyl, cyclohexyl, aryl, etc.), while alkenyliodonium tosylates 176 are formed from non-sterically hindered terminal alkynes or from internal alkynes. 

Various flve-membered heterocycles can be prepared by inter- or intramolecular addition/cyclizations of appropriate nucleophiles with alkynyliodonium salts via alkylidene carbene intermediates [856, 978, 979]. The intermolecular variant of this cyclization has been employed in the synthesis of 3-substituted-5,6-dihydroimidazo[2,l-( ]thiazoles [997], 2-substituted imidazo[l,2-a]pyrimidines [998] and 2-substituted-imidazo[l,2-fl]pyridines [999]. In a representative example, 2-substituted imidazo[l,2-fl]pyridines 744 were synthesized in good yield by cyclocondensation of 2-aminopyridine (742) with alkynyl(phenyl)iodonium tosylates 743 under mild conditions (Scheme 3.293) [999]. The mechanism of this cyclization involves... 

The reaction of lithium or sodium arylteUurolate with alkynyl phenyl iodonium triflates or tosylates. ... 

Alkynyl(phenyl)iodonium salts can be efficiently coupled with various organo-copper reagents. Direct coupling of alkynyliodonium tosylates 132 with vinyl-... 

The iodonium triflate (460 mg, 1 mmol) was added to a stirred slurry of anhydrous sodium p-toluene sulphinate (180 mg, 1.01 mmol) in dichloromethane (15 ml) at 20°C under nitrogen. After 15 min water (10 ml) was added and the phases were separated the aqueous layer was extracted with additional dichloromethane (2 x 5 ml), and the combined organic extracts were dried. The filtered solution was treated with hexanes (30 ml) and concentrated. The solid residue was purified by radial chromatography (silica gel, 200-400 mesh, dichloromethane-hexanes) to afford 3-tosyl-bicyclo[3.2.0]-3-heptene-2-one (197 mg, 75%), m.p. 164-165°C. The method is general for the preparation of sulphones with a cyclopentenone moiety other alkenyl iodonium salts gave alkynyl sulphones with sulphinates (Section 9.4.4). 

The original procedure involved the coupling of aryl bromides with secondary amines. However, since then the scope has been expanded to include substrates such as aryl iodides, chlorides, fluorides, triflates, tosylates, nonaflates, iodonium salts, and even boronic acids. While the reaction has not been extensively utilized with vinyl or alkynyl substrates, it can be performed with various heteroaryl halides. Similarly, numerous types of nitrogen-containing coupling partners, including primary amines, imines, various azoles, lactams, and simple amides, can now be used in this reaction. 

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. 

In a similar manner, decomposition of alkynyl(phenyl)iodonium phosphates 98 affords acetylenic phosphate esters (equation 64) . This reaction does not require any catalyst, since alkynyl(phenyl)iodonium phosphates 98 are substantially less stable than tosylates 97, and smoothly decompose upon standing at room temperature for a few hours in CH2CI2 or CHCI3 yielding alkynyl phosphates 95 and iodobenzene as the by-product. 

---