Butyne-l,4-diol

Butynediol. Butynediol, 2-butyne-l,4-diol, [110-65-6] was first synthesized in 1906 by reaction of acetylene bis(magnesium bromide) with paraformaldehyde (43). It is available commercially as a crystalline soHd or a 35% aqueous solution manufactured by ethynylation of formaldehyde. Physical properties are Hsted in Table 2. 

Ethynylation. Base-catalyzed addition of acetylene to carbonyl compounds to form -yn-ols and -yn-glycols (see Acetylene-DERIVED chemicals) is a general and versatile reaction for the production of many commercially useful products. Finely divided KOH can be used in organic solvents or Hquid ammonia. The latter system is widely used for the production of pharmaceuticals and perfumes. The primary commercial appHcation of ethynylation is in the production of 2-butyne-l,4-diol from acetylene and formaldehyde using supported copper acetyHde as catalyst in an aqueous Hquid-fiHed system. 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

Diol Components. Ethylene glycol (ethane 1,2-diol) is made from ethylene by direct air oxidation to ethylene oxide and ring opening with water to give 1,2-diol (40) (see Glycols). Butane-1,4-diol is stiU made by the Reppe process acetylene reacts with formaldehyde in the presence of catalyst to give 2-butyne-l,4-diol which is hydrogenated to butanediol (see Acetylene-DERIVED chemicals). The ethynylation step depends on a special cuprous... 

Acetylenic compounds have often been used as precursors to certain pyrroles. Thus, 2-butyne-l,4-diol reacts with aniline ia the presence of alumina to produce A/-phenylpyrrole [635-90-5] (27). 

Chemical Designations-SynotQ mr 2-Butyne-l,4-Diol l,4-Dihydroxy-2-Butyne Chemical Formula HOCHjCbCCHjOH. 

Finally, a special example of transition metal-catalyzed hydrogenation in which the ionic liquid used does not provide a permanent biphasic reaction system should be mentioned. The hydrogenation of 2-butyne-l,4-diol, reported by Dyson et al., made use of an ionic liquid/water system that underwent a reversible two-... 

Acetylenic compounds have been described for inhibition in acid solutionsTypical inhibitors include 2-butyne-l,4-diol, l-hexyne-3-ol and 4-ethyl-l-octyne-3-ol. 

Butyne-l,4-diol and propargylalcohol are produced by reaction between formaldehyde in aqueous solution and gaseous acetylene in the presence of a copper acetylide catalyst supported on nickel. The process is carried out by trickle-flow operation (BIO, S4). 

Hydrogenation reactions, particularly for the manufacture of fine chemicals, prevail in the research of three-phase processes. Examples are hydrogenation of citral (selectivity > 80% [86-88]) and 2-butyne-l,4-diol (conversion > 80% and selectivity > 97% [89]). Eor Pt/ACE the yield to n-sorbitol in hydrogenation of D-glucose exceeded 99.5% [90]. Water denitrification via hydrogenation of nitrites and nitrates was extensively studied using fiber-based catalysts [91-95]. An attempt to use fiber-structured catalysts for wet air oxidation of organics (4-nitrophenol as a model compound) in water was successful. TOC removal up to 90% was achieved [96]. 

Removal of formaldehyde from aqueous 2-butyne-l,4-diol, or a similar solution, which is relevant in the subsequent manufacture of c -2-butene-l,4-diol, by batch reactive distillation with methanol or ethylene glycol in the presence of Indion 130 as catalyst has also been reported 98% conversion of formaldehyde was obtained by reactive distillation with 7 times the stoichiometric quantity of methanol, compared to 15% conversion obtained in a closed system (Kolah and Sharma, 1995). 

Going to extremes, the reactivity of internal acetylenic triple bonds compared with terminal olefinic double bonds was also checked. Diallyl ethers of commercial 2-butyne-l,4-diol and 3-hexyne-2,5-diol are available in high yield by phase transfer etherification. They are reacted under essentially the same conditions as those described in section 3.1, with the double bond now being in 100 percent excess at the beginning (Eq. 4). 

The same type of reaction has been used just recently by Sonnek and coworkers [17] to get access to di(meth)acrylate structures added to siloxanes via hydrolytically stable silicon-carbon bond formation. 2-Heptamethyltrisiloxanylbut-2-en-l,4-diylbismethacrylate is accordingly prepared in 90 % yield by hydrosilylation of the bismethacrylate of 2-butyne-l,4-diol. 

In contrast, synthesis of 3,4-diphosphorylthiophenes requires more elaboration because of low reactivity of 3,4-positions of thiophene and unavailability of 3,4-dihalo or dimetallated thiophenes. Minami et al. synthesized 3,4-diphosphoryl thiophenes 16 as shown in Scheme 24 [46], Bis(phosphoryl)butadiene 17 was synthesized from 2-butyne-l,4-diol. Double addition of sodium sulfide to 17 gave tetrahydrothiophene 18. Oxidation of 18 to the corresponding sulfoxide 19 followed by dehydration gave dihydrothiophene 20. Final oxidation of 20 afforded 3,4-diphosphorylthiophene 16. 3,4-Diphosphorylthiophene derivative 21 was also synthesized by Pd catalyzed phosphorylation of 2,5-disubstituted-3,4-dihalothiophene and converted to diphosphine ligand for Rh catalysts for asymmetric hydrogenation (Scheme 25) [47],... 

Butyne-l,4-diol has been hydrogenated to the 2-butene-diol (97), mesityl oxide to methylisobutylketone (98), and epoxides to alcohols (98a). The rhodium complex and a related solvated complex, RhCl(solvent)(dppb), where dppb = l,4-bis(diphenylphosphino)butane, have been used to hydrogenate the ketone group in pyruvates to give lactates (99) [Eq. (15)], and in situ catalysts formed from rhodium(I) precursors with phosphines can also catalyze the hydrogenation of the imine bond in Schiff bases (100) (see also Section III,A,3). 

In 1982, the ruthenium-catalyzed isomerization of 2-butyne-l,4-diol to butyrolactone was reported. This reaction was proposed to proceed through initial isomerization of 2-butyne-l,4-diol to a,/3-unsaturated aldehyde followed by cyclization and double bond isomerization (Scheme 52).91... 

A distannation product of 2-butyne-l,4-diol oxidatively cyclizes to provide 3,4-bis(stannyl)furan, which then undergoes palladium-catalyzed cross-coupling with an aryl iodide to give 3,4-diarylfuran (Scheme 31).152,153... 

Recently, Chaudhari compared the activity of dispersed nanosized metal particles prepared by chemical or radiolytic reduction and stabilized by various polymers (PVP, PVA or poly(methylvinyl ether)) with the one of conventional supported metal catalysts in the partial hydrogenation of 2-butyne-l,4-diol. Several transition metals (e.g., Pd, Pt, Rh, Ru, Ni) were prepared according to conventional methods and subsequently investigated [89]. In general, the catalysts prepared by chemical reduction methods were more active than those prepared by radiolysis, and in all cases aqueous colloids showed a higher catalytic activity (up to 40-fold) in comparison with corresponding conventional catalysts. The best results were obtained with cubic Pd nanosized particles obtained by chemical reduction (Table 9.13). 

Table 9.13 Comparison of colloidal and heterogeneous catalysts in the hydrogenation of 2-butyne-l,4-diol. (Adapted from [89])...

The stereospecific reduction of a 2-butyne-l, 4-diol derivative and silver( I)-mediated cyclization of the resulting allene were successively applied to a short total synthesis of (+)-furanomycin 165 (Scheme 4.42) [68], Stereoselective addition of lithium acetylide 161 to Garner s aldehyde in the presence of zinc bromide afforded 162 in 77% yield. The hydroxyl group-directed reduction of 162 with LiAlH4 in Et20 produced the allene 163 stereospecifically. Cyclization followed by subsequent functional group manipulations afforded (+)-furanomycin 165. 

Bis(cyclopentadienyl)hexafluoro-2-butynechromium, 3636 Bis(dibutylborino)acetylene, 3775 Bis(dipropylborino)acetylene, 3670 Butoxyacetylene, 2428 2-Butyne-l,4-diol, 1526... 

In-the Reppe process, formaldehyde and acetylene are reacted in.the presence of a.copper acetylide catalyst to give 2-butyne-l,4-diol. That compound is then hydrogenated to give BDO. 

The influence of a number of organic ad-ditives-2-butyne-l,4-diol [388], 2-picoline [389], sodium lauryl sulfate [372],... 

Acetylenic precursors employed in the syntheses of sugars may be divided into three groups (a) aldehydes (usually in the form of acetals), (b) alkyl alkynyl ethers, and (c) alkynols or alkynediols. Some of them are commercially available (for example, 2-butyne-l,4-diol), and others are prepared by Grignard-type reactions between 1-alkynylmag-nesium halides or lithium alkynes and suitable aldehydes, ketones, or epoxides. In this way, the synthesis of substrates having the desired number of carbon atoms, as well as the necessary functional groups, can be achieved. The next step consists in partial saturation of the triple bond to afford the desired cis- or trans-alkene. ct.s-Alkene systems... 

Fraser and Raphael devised a synthesis of 2-deoxy-Di.-cn///irope n to se (2) starting from 2-butyne-l,4-diol. Monobenzov lation, followed by reaction with phosphorus tribromide, furnished l-(ben-zoyloxy)-4-bromo-2-butyne (151). Reaction of 151 with diethyl sodio-... 

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