Alkynyl phosphates

Reactions of lithium alkynolates with dialkylchlorophosphates afford alkynyl phosphate esters as the major products (equation 14). However, reactions with acyl chlorides under similar conditions results in both O-acylation (product 20) and C-acylation (product 21) (equation 15). ... 

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. 

More recently we have reported the preparation of alkynyl esters by the reaction of lithium alkynolates with the corresponding acid chlorides (equations 14 and 15, Section II.B.2). This method works well for the synthesis of alkynyl phosphates, however, it has only limited applicability in the preparation of alkynyl carboxylates. ... 

Hydroxy(dialkylphosphoryloxy)iodo]benzenes 177 (Section 2.1.7) react with terminal alkynes under anhydrous conditions to afford alkynyl phosphates 178 (Scheme 3.76) via intermediate formation of the respective alkynyl(phenyl)iodonium phosphates [239]. 

A wide variety of aryl iodides undergo palladium catalyzed coupling with tert-butyl ethynyl ether giving intermediate tert-butyl arylethynyl ethers which upon in situ thermolysis in toluene containing morpholine give intermediate aryUcetenes that are captured as the morpholinyl esters (Scheme 4.22). Alkynyl phosphates act as nucleophiles toward histidine residues in phosphotriesterase under physiological conditions, and this has been proposed to involve ketene formation in a phosphotriesterase catalyzed reaction (Eqn (4.61)). ... 

Addition to linear 1,1-disubstituted allylic acetates is slower than addition to monosubstituted allylic esters. Additions to allylic trifluoroacetates or phosphates are faster than additions to allylic carbonates or acetates, and reactions of branched allylic esters are faster than additions to linear allylic esters. Aryl-, vinyl, alkynyl, and alkyl-substituted allylic esters readily undergo allylic substitution. Amines and stabilized enolates both react with these electrophiles in the presence of the catalyst generated from an iridium precursor and triphenylphosphite. 

In general, allylic and propargyllic electrophiles are much more reactive than alkenyl and alkynyl electrophiles. Thus, a wide variety of electrophiles containing halogens, e.g. I, Br, and Cl, and oxygen groups, e.g. sulfonates, phosphates, carboxylates, carbonates, alkyl and aryl ethers, and even silyl... 

Woerpel and Clark identified silver phosphate as the optimal catalyst to promote di-ferf-butylsilylene transfer from cyclohexene silacyclopropane to a variety of substituted alkynes (Scheme 7.25).95 While this silver salt exhibited attenuated reactivity as compared to silver triflate or silver trifluoroacetate, it exhibited greater functional group tolerance. Both di- and monosubstituted silacyclopropenes were easily accessed. Terminal alkynes are traditionally difficult substrates for silylene transfer and typically insert a second molecule of the starting acetylene.61,90 93 Consequently, the discovery of silver-mediated silylene transfer represents a significant advance as it enables further manipulation of monosubstituted silacyclopropenes. For enyne substrates, silylene transfer the alkynyl group was solely observed. The chemoselectivity of the formation of 99f was attributed to ring strain as theoretical calculations suggest that silacyclopropenes are less strained than silacyclopropanes.96 97... 

Alkynyl dialkyl phosphates of the general formula RC=COPO(OR )2, were prepared by a similar spontaneous decomposition of the less stable salts RC=CI+ PhC OPO(OR)2, some of which are isolable alternatively, either alkynes and [hydroxy(dialkylphosphoryloxy)iodo]benzene or alkynysilanes and iodosylben-zene-boron trifluoride can be used [63]. 

The same reagent with terminal alkynes also afforded a-ketol phosphates [20], or alkynyl dialkyl phosphates (see Section 9.4.3) [19], depending on the conditions. 4-Pentenoic acids underwent phosphoryloxylactonization [18]. 

Reaction with an amine, AIBN, CO and a tetraalkyltin catalyst also leads to an amide.Benzylic and allylic halides were converted to carboxylic acids electroca-talytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions.Allylic (9-phosphates were converted to allylic amides with CO and ClTi=NTMS, in the presence of a palladium catalyst. Terminal alkynes were converted to the alkynyl ester using CO, PdBr2, CuBr2 in methanol and sodium bicarbonate. ... 

R = alkyl, allyl, alkenyl, alkynyl, aryl R = alkyl, OH, 0-alkyl R = alkenyl, aryl, alkyl X = Cl, Br,l, OTf, OPO(OR)2 (enol phosphate) base = Na2C03, Ba(OH)2, K3PO4, CS2CO3, K2CO3, TlOH, KF, CsF, BU4F, NaOH, M CO-alkyl)... 

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. <... 

A second type is the reaction of alkynylphenyliodonium tosylates with benzoate loaded ion exchange resin. Alkynyl benzoates (86) and phenyl iodide were the products which could result from ligand coupling on the intermediate alkynylphenyliodonium benzoates. However, isolation of these intermediates has not been possible. 1 6 (Scheme 5.8) The same reaction with diethyl phospHate led to the corresponding phosphate esters (87). 1 5,197... 

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