Acetylenic diols

The various products obtained from acetylenic diols 54 in the presence of acids suggest the formation and interconversion of acetylene-allene-diene cationoid intermediates (equation 18)33. The allene intermediates can be sometimes isolated and they were reported as participants in the acid-catalyzed reactions of alkynylpyrylium salts 55, a driving force of which is an aromatization of the pyrane ring (equations 19-21)34,35. 

Aasen, A. J., J. R. Hlubucek, and C. R. Enzell. Tobacco chemistry. The structures of four stereoisomeric 8,12 XI-epoxylabd-14-en-13-XI-ols isolated from Greek Nicotiana tahacum. Acta Chem Scand Ser B 175 29 589. Fujimori, T., R. Kasuga, H. Kaneko, and M. Noguchi. A new acetylenic diol, 3 hydroxy-7,8-dihydro-betaionol, from burley Nicotiana tahacum. Phytochemistry 1975 14 2095. 

The formation of potassium acetylide is presumably an equilibrium yet it appears to be possible to convert the ketones completely into the ethynyl carbinols in greater than 90% yield, using a 1 1 molar ratio of r-BuOK and ketone. In the case of cyclohexanone even a 1 2 molar ratio gave > 85% yield of ethynylcyclohexanol, suggesting that a catalytic amount of starting base may suffice. However, the formation of acetylene diols appears to become increasingly important as the ratio r-BuOK/ketone is diminished. 

The acetylenic diol Me2C(OH)-C C-C(OH)Me2 (ac) forms complexes of the types K PtCl3ac] and cis- and 2mns-[PtCl2(ac)(am)] (am = amine), by reactions commonly used in the preparation of olefin complexes 23, 25,... 

Other Degraded Carotenoids. The acetylenic diol (115), prepared by reaction of but-3-yn-2-ol dianion with 2,6,6-trimethyl-4,4-ethylenedioxycyclohex-2-en-l-one (116), afforded 3,5,5-trimethyl-4-(2-butenylidene)-cyclohex-2-en-l-one (117), a major constituent of Burley tobacco, on LiAlH4 reduction and hydrolysis.53... 

Figure 8. Influence of glycoconjugation on the rate of reaction products 19 and 20 formed from acetylenic diol 18 and its 9-O-glucoconjugate 16 according to Skouroumounis et al. (39).

A by-product from the reaction of acetone and sodium acetylide is the acetylenic diol, (CHj)2C(OH)C= C(OH)(CH,)j, formed by condensation of two molecules of acetone with one molecule of sodium acetylide. A general method for the preparation of acetylenic diols of this type is from calcium carbide, potassium hydroxide, and ketones. Ciethynyl glycols in which the triple bonds are separated by two or four carbon atoms are made from sodium acetylide and a- or /S-diketones. ... 

The ring-closure mechanism of 2-chloroethanol has been studied on the basis of kinetic and equilibrium chlorine isotope effects. Epoxidation of the terminal double bond of farnesyl acetate has been achieved via the bromohydrin, obtained with NBS. A stereospecific method has been elaborated for the preparation of 1-alkynyloxiranes, starting from the monotosylate ester of acetylenic diols. 1-Alkynyloxiranes are also formed from a-hydroxy quaternary ammonium salts in alkaline medium (Eq. 57). ... 

The application of the reaction of the allenyltitanium Ti[RG=GH(propargyl)](OPr1)3 to generate acetylenic diol systems has been studied. (Scheme 129).41... 

Rearrangements.— Both propargyl alcohol and propargyl mercaptan give the corresponding allenylphosphonates (90) and (91) on reaction with tervalent phosphorus acid chlorides. In the case of a similar reaction with the acetylenic diol (92) a double rearrangement occurs to give the diphosphonate (93),... 

The reagent has also been used for the synthesis of acetylenic diols.4 Thus 3-methyl-l-butyne-3-ol (6) is heated with two moles of the reagent to form the dilithio derivative. Cyclohexanone is added and the diol (7) is obtained in 60% yield. The reaction can also be carried out with acetylene and two different ketones. 

Acetylenic diols. Ref. 4, 2, 289 Definitive paper, S. Watanabe, K. Suga, and T. Suzuki, Canad. J. Chem., 47, 2343 (1969). Naphthalene-lithium was found to be superior to other metalating agents (naphthalene-sodium, n-butylmagnesium bromide) in this synthesis. 

Sporadic reports of stereoselectivity in such cyclizations appear, notably in the work of Noza-ki116-117 and a report from Witteveen and van der Weerdt118. For example, treatment of the chiral acetylenic diol 5 in hot formic acid affords the cyclopentenone 6 in modest yield. 

The leaving group X in (23) will be derived from a hydroxyl group as usual. Hence (24) could be made from the symmetrical epoxide (25) choosing the correct stereochemistry to give (24) by Sn2 inversion. The required stereochemistry is cis so that we can make (24) from the readily available acetylenic diol (26) by simple steps. 

A key intermediate for the synthesis of symmetrical central building blocks is the acetylenic diol 42 which can easily be synthesized by a Grignard reaction of acetylene dimagnesium dibromide (43) with 2-methylprop-2-enal (44) (Scheme 11). 

Fujimori, T., R. Kasuga, H. Kaneko, and M. Noguchi A new acetylenic diol, 3-hydroxy-7,8-dehydro-P-ionol, from hurley Nicotiana tabacimr. Phytochemistry 14... 

Acetylenic diols, potential building blocks for the synthesis of L-hexoses and L-pentoses, are available with either syn or anti configuration using TBPS-protected L-lactic acid derivatives as the chiral source (Scheme 108). 

For a synthesis of p,p-carotene (3), once practised industrially [9], the di-Grignard reagent of acetylene f77j is prepared by bubbling acetylene into an ethereal solution of ethyl magnesium bromide, and is then reacted with two equivalents of the Gi9-aldehyde 72 to give the acetylenic diol 13, from which P,p-carotene (3) is obtained by dehydration, Lindlar hydrogenation, and isomerization (Scheme 3). 

The acetylenic diol 1 has been used for the preparation of the phosphonium salts 9 (route 7 —and 10 (route 7 7772 70) which have been applied to the synthesis of p,p-carotene (3) [6]. The phosphonium salts 9 and 70 also proved their utility in the syntheses of 7,8-didehydroastaxanthin (402) and 7,8,7 ,8 -tetradehydroastaxanthin (400) [7] and of optically active carotenoids with 3,5,6-trihydroxy-5,6-dihydro-p-end groups [8]. Despite these interesting examples it is noteworthy that, in general, the diphosphonates are much better reagents for double olefination than the corresponding diphosphonium salts [9]. 

Synonyms 2,5-Dihydroxy-2,5-dimethyl-3-hexyne 2,5-Dimethyl-2,5-dihydroxy-3-hexyne 2,5-Dimethyl-3-hexyne-2,5-diol Definition Di-tertiary acetylenic diol Empirical C8H14O2 Formula (CH3)2COHCCCOH(CH3)2... 

Various other acetylenic substrates can also be used for the synthesis of furans by intramolecular gold-catalyzed C-O bond formation. Thus, acetylenic diols gave a variety of monosubstituted, disubstituted, or trisubstituted fiirans by dehydrative cyclization in the presence of 2 mol% Au[P(r-Bu)2(o-biphenyl)]Cl/AgOTf or AuCl at 0 °C (Scheme 4-8In the latter case, the catalyst loading can be decreased to 0.05 mol% by scavenging water with activated molecular sieves and conducting the reaction in refluxing THF. 

The olfines contain acetylenic alcohol and acetylene diol. These compounds are basically acetylene-based polyoxyethylene oxide surfactants. Acetylenic alcohols themselves are highly volatile surfactants. An example of an acetylenic alcohol is propargyl alcohol, also known as propyn-l-ol. Acetylenic nonionic surfactants and their methods of synthesis have been described in detail (79). 

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