Hydroxy Acetylenes

Functional groups include allene, acetylene, hydroxy, methoxy, epoxy, keto, aldehyde, carboxylate, lactone, acyl ester, glycoside, glycosyl ester and sulphate. Carotenoids with elements other than oxygen directly attached to the carbon skeleton have not been found in Nature. 

Coke and Richon have constructed the 8-lactone framework of n-hexadecalactone, the proposed pheromone isolated from Vespa orientalis, through lactonization of a hydroxy acid intermediate [39] (Scheme 3). The optically pure amino alcohol 22 obtained by resolution was converted to the optically active epoxide 23 by quatemization, followed by Hofmaim elimination. Addition of the dianion of propiolic acid to epoxide 23, and subsequent reduction of the resulting acetylenic hydroxy acid with hydrogen and palladium, provided the saturated hydroxy acid 25, which spontaneously cycUzed to afford 8-lactone 12. In a similar way, the enantiomer of amino alcohol 22 was also transformed into the antipode of lactone 12. Furthermore, using this method, any terminal epoxide can easily be converted to the corresponding saturated 8-lactone in two steps. 

Apart from lactic and hydroxyacetic acids, other a- and P-hydroxy acids have been small-volume specialty products produced in a variety of methods for specialized uses. y-Butyrolactone [96 8-0] which is the monomeric inner ester of y-hydroxybutyric acid [591-81-17, is a large-volume chemical derived from 1,4-butanediol (see Acetylene-derived chemicals). 

Since 17a-ethynyl-17 -hydroxy steroids are so readily prepared, they represent attractive starting materials for conversion to 20-ketopregnanes. Standard methods for the hydration of aliphatic acetylenes (e.g, mercuric salts alone, with aniline, or with BF3) give variable results, and sometimes no product at all, due to D-homo rearrangement. 233,235,265-7 mercury... 

In this case, the low-cost 2-methyl-2-hydroxy-3-butyne is used as a convenient source of acetylene. 

The Fiesselmann thiophene synthesis involves the condensation reaction of thioglycolic acid derivatives with a,P-acetylenic esters, which upon treatment with base results in the formation of 3-hydroxy-2-thiophenecarboxyIic acid derivatives. 

Soon after the 1946 report by Woodward on the condensation of thioglycolic acid and a,P-unsaturated esters in the presence of base to produce structures like 2-carbomethoxy-3-ketotetrahydrothiophene 4, Fiesselmann extended this reaction to a,p-acetylenic esters for the direct preparation of 3-hydroxy-2-thiophenecarboxyIic acid derivatives. ... 

The mechanism of the Fiesselmann reaction between methylthioglycolate and a,P-acetylenic esters proceeds via consecutive base-catalyzed 1,4-conjugate addition reactions to form thioacetal Enolate formation, as a result of treatment with a stronger base, causes a Dieckmann condensation to occur providing ketone 8. Elimination of methylthioglycolate and tautomerization driven by aromaticity provides the 3-hydroxy thiophene dicarboxylate 9. 

Dihydro-2f/-pyran-2-one has been prepared by reductive cycliza-tion of 5-hydroxy-2-pentynoic acid [2-Pentynoic acid, 5-hydroxy-], which is obtained in two steps from acetylene [Ethyne] and ethylene oxide [Oxirane] 3 and by the reaction of dihydropyran [277-Pyran, 3,4-dihydro-] with singlet oxygen [Oxygen, singlet].4,5 2ff-Pyran-2-one has been prepared by pyrolysis of heavy metal salts of coumalic acid [2//-Pyran-5-carboxylic acid, 2-oxo-],8 by pyrolysis of a-pyrone-6-carboxylic acid [211 - Pyran-6-carboxyl ic acid, 2-oxo-] over copper,7 and by pyrolysis of coumalic acid over copper (66-70% yield).8... 

Disconnection of the ether la now a good idea as it leaves an ct-hydroxy ketone to be made by acyl anion equivalent addition. We prefer (10) as the acetylene anion can then serve as synthon (4). 

Now the ether may be disconnected, diol (13) being the obvious starting material. This contains an i-hydroxy ketone so we might consider disconnecting an acyl anion equivalent from a ketone. If we use an acetylene, the starting material (14) is symmetrical so hydration presents no problems,... 

Reagents are available nowadays for acyl anions other than (4). Thus when Heathcock made the ketone (16), which he used in stereoselective aldol reactions, he needed a-hydroxy ketone (17), This required synthon (18) for which an acetylene is not a good choice as there are as yet no means of controlling the reglo-selectivity of hydration of (19). 

Workers studying the eyelisation of acetylenic alcohols decided to make (30), Disconnection of the acetylene leaves a-hydroxy ketone (31), Since this ketone is blocked on one side by the aromatic ring it is reasonable to make (31) from (33) via bromoketone (32). Ana lysis... 

Hydroxy(tosyloxy)iodobenzene 2014 reacts with phenyltrimethylsilane 81 in boiling acetonitrile to give diphenyliodonium tosylate 2015 and trimethylsilanol 4 or HMDSO 7 [184, 185]. Likewise, treatment of 2,5-bis(trimethylsilyl)furan 2016 with 2014 in boiling acetonitrile/methanol affords 78% iodonium tosylate 2017 and trimethylsilanol 4 [185]. In the presence of Bp3-OEt2 iodosobenzene oxidizes allyl-trimethylsilanes such as 2018 to unsaturated aldehydes such as 2019 in 63% yield, with formation of iodobenzene and trimethylsilanol 4 [186]. Analogously, vinyltrimethylsilanes such as (Z)-l-trimethylsilyl-2-phenylethylene 2020 afford, via 2021, acetylenes such as phenylacetylene in 61% yield and iodobenzene and trimethylsilanol 4 [187] (Scheme 12.54). 

Fatty Acid Esters. Defoamers that are more environmentally acceptable than convential products are based on fatty acid esters of hydroxy alcohols, such as sorbitan monooleate [1908] or sorbitan monolaurate in combination with diethylene glycol monobutyl ether as a cosolvent [451]. These defoamer compositions are as effective as conventional materials, for example, those based on acetylenic alcohols are less toxic, especially to marine organisms, and are readily biodegradable. The defoamer compositions are used in water-based hydrocarbon well fluids during oil/gas well drilling, completion, and workover, especially in marine conditions. 

C-TMS protection of the alkyne provided acceptable yields of 3-substituted indole as long as the hydroxy group was protected with a stable group. Purple colored impurities, one of which has been identified as azulene 45, were seen in both coupling reactions using C-TMS-alkynes such as 36 and 40d (Scheme 4.9). The azulene was presumably formed through the dimerization of acetylenes... 

A reinvestigation of the reactions of 3,4-dichloro- and 3-chloroH-hydroxy thiadiazoles with a variety of acetylene nucleophiles (NaC=CNa, I, iC=C-TMS, LiC=C-SnM e3) showed consumption of the starting thiadiazoles with no significant higher molecular weight products being formed <2004TL5441>. 

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