Ynols—

First example for the isomerization of propargylic alcohols to isolable a,(3-enals was reported in 1989. A variety of prop-2-ynols can be isomerized to a,/3-unsaturated aldehydes in the presence of a catalytic amount of RuCl2(PPh3)3/ Pr 3P (Scheme 53).92... 

The most unique feature of furan synthesis using palladium chemistry is heteroannulation. Enones, ynones and ynols all have been annulated into furans and benzofurans. More importantly, trapping the reactive Pd(II) intermediates at different stages with electrophiles offers unique opportunities to synthesize substituted furans and benzofurans. 

The addition of secondary phosphines H PR2 to prop-2-ynols in the presence of RuCl (C5Me5)(cod) or RuCl(C5Me5)(PPh3)2 provides the first regio- and stereo-selective direct hydrophosphination of propargylic alcohols and leads to bifunctional... 

The extended pH-independent branch seen in the pH profile of phenylynol (Fig. 6) has an entirely different origin due to the high acidity of the ynol, pAT <2.7, the ynol anion is predominant over the whole observable pH range, and the pH-independent process observed above pH 5 is its protonation by solvent water, Ee K + HOe. 

Isomerization of 2-ynols.4 This Ru complex in combination with a trialkyl-phosphine is an effective catalyst for isomerization of 2-ynols to a,p-enals in refluxing toluene. 

A. J. Kresge, Flash Photolytic Generation and Study of Reactive Species From Ends to Ynols, Acc. Chem. Res. 1990, 23, 43-48. 

Most of the compounds that you have encountered in this text so far have been fairly simple. In addition to any carbon-carbon double or triple bonds, they have contained only one functional group and could be named by using suffixes such as -ynol or -dienone. However, for a compound that contains more than one heteroatom functional group, only one of these functional groups can be designated in the suffix. For example, consider the following compound, which has both alcohol and ketone functional groups ... 

Homopropargylic alcohols (but-3-ynols) as well as propargylic epoxides are suitable products to form cyclic ruthenium alcoxycarbenes upon intramolecular nucleophilic addition of the OH group to the electrophilic a-carbon of ruthenium vinylidene species. The recovery of the organic ligand as a lactone... 

The ability of the binuclear complex [Cp RuCl(p2-SR)2RuCl(Cp )] to generate cationic allenylidene complexes by activation of terminal prop-2-ynols in the presence of NH4BF4 as a chloride abstractor opens the way to a variety of catalytic transformations of propargylic alcohols involving nucleophilic addition at the Cy atom of the ruthenium allenylidene intermediate (Scheme 19). This leads to the formation of a functional ruthenium vinylidene species which tau-tomerizes into an -coordinated alkyne that is removed from the ruthenium centre in the presence of the substrate. 

Ethylenediamine (98) and l-methylprop-2-ynol (99) gave 2,3-dimethyl-5,6-di-hydropyrazine (100) [Hg(OAc)2, CHC13, reflux, 7 h 51%) homologues likewise.210... 

In this paper the pA a of phenylhydroxyacetylene (PhC=COH) is reported to be <2.8. Since the tautomeric phenylketene (PhCH=C=0) is more stable than the ynol, pATa for the ketene is greater. 

Oxabenzonorbornenes undergo a Ru-catalysed reaction with prop-2-ynols under mild conditions to give 1-substituted isochromenes (Scheme 18) <06EJO5449>. 

SYNS A YL METHYL CARBINOL HEPT.YNOL-2 2-HYDROXYHEPTANE METHYL AMYL CARBINOL... 

AETHYLCARBAMAT (GERMAN) see UVAOOO AETHYLCHLORID (GERMAN) see EHHOOO AETHYL-CHLOR YNOL see CHGOOO AETHYL-2-(3, 5 -DIJOD-4 -OXYBENZOYL)-3 CUMARON see EID200... 

This homologation via lithium ynolates has been used to prepare silyl ynol ethers, as described in Section V. 

Ynol tosylates are synthesized from terminal alkynes via a unique sequence (equation 10). The hypervalent organoiodine compound 32, prepared by treatment of iodosoben-zene diacetate with /i-toluenesulfonic acid, reacts with the terminal alkynes 31 to give the iodonium tosylates 33, which are then treated with 10 mol% of CuOTf or AgOTf to afford the ynol tosylates 34. Finally, the ynol tosylates 34 are converted into lithium ynolates 35 by treatment with MeLi. The ynolates are trapped with r-butyldimethylsilyl chloride, triethylgermyl chloride and tributylstannyl chloride to give the silyl ynol ethers 36, the germyl ketenes 37 and the stannyl ketene 38. ... 

Flash photolysis of phenylhydroxypropenone (51) in aqueous solution gives pheny-lacetic acid 53 through the ynolate 52 as a short-lived reaction intermediate (equation 21) ". Kinetic experiments revealed that the corresponding aryl ynols ArC=COH are strong acids with pKa < 2.8 5,... 

Lithium ynolates are stable and keep their reactivity at 0 °C under inert gas for several days, but they decompose in 1 day at 20 Silyl ynolates (sUyl ynol ethers) are stable for a long period and they can be purified by distillation, but they are labile to acids (Section V). The stability of ynolates of metals other than hthium is unknown. 

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