Alkyne-Alcohols

The functional group transforms in this section are summarized as 

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Enamines can also be converted to amino alcohols via hydroboration. Allene-boranes react with aldehydes to give alkyne-alcohols. ... 

A novel gold catalyzed example of three-component addition was recently reported by Shi et al. (Equation 8.44) [106]. Terminal aryl alkynes, alcohols and 2-(arylmethy-lene) cyclopropylcarbinols provided an intermolecular tandem hydroalkoxylation/ Prins-type reaction to form 3-oxabicyclo[3.1.0]hexanes from simple materials and under mild conditions, catalyzed by the system AuClPPh3/AgOTf. The proposed mechanism for this reaction is shown in Scheme 8.19. 

The reaction of a bis-alkynic alcohol (103) with aqueous dimethylamine gives dimethyl-aminofuran (104) (74IZV206). trans-Enynols cyclize presumably through a cis intermediate with base (75RTC70) or mercury(II) sulfate, a method used for the synthesis of the terpenoid bilabone (105) (69JOC857). 

Several preparative methods exist for the synthesis of 3(2//)-dihydrofuranones. 2,5-Disubstituted or 2,2,5,5-tetrasubstituted 3(2i/)-dihydrofuranones are usually prepared by reaction of sodium or lithium acetylide with a ketone to yield an alkynic alcohol which is then treated with a carbonyl compound in the presence of base to afford alkynic diols. Mercury catalyzed hydration of the resultant diols in the presence of acid affords the furanones in good yields (76JMC709). 

Several cyclofunctionalization reactions of alkynic alcohols are synthetically useful. Metal ion-promoted cyclofunctionalization of ris-2-propargylcyclopentanol systems proceeds by the 5-exo mode (equation 77 and Table 23).197 Protiodemetallation or reductive demetallation provides the cyclic enol ether in high yields. This method has been used by Noyori in the synthesis of prostacyclin (PGh).197b,197c Reactions with catalytic amounts of mercury(II) or palladium(II) salts gave the endocyclic enol ether as the major product.197 -198 A related cyclization with Ag2C03 has been reported by Chuche.191 Schwartz... 

In certain other systems, there is compelling evidence for the insertion into a metal-caiboxylate complex (equation 37). For example, in the synthesis of a-methylene-y-lactones from alkynic alcohols,70,71 no double bond rearrangement to a butenolide occurs, a reaction shown to take place in the presence of transition metal hydrides. The source of the vinyl proton (deuterium) on the a-methylene group is indeed the alcohol function. Finally, palladium carboxylate complexes containing alkynic (equation 40) or vinyl tails (equation 41) can be isolated and the corresponding insertion reaction can be observed. 

The synthesis of a-methylenelactones from alkynic alcohols can be effected in 84% yield utilizing HPt(SnCb)(PPh3)2 (equation 53)84 This is essentially the same a-methylenelactone synthesis elegantly developed earlier utilizing a palladium catalyst (Table 7).85 The starting tram alkynic alcohols are ob-... 

Alkynes Alcohols Aldehydes and Ketones Acids and Derivatives... 

Begin to recognize the important functional groups alkene, alkyne, alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, nitrile, amide, thiol, and thioether. 

N—C—O + C—C. The construction of the oxazole ring by the condensation of a-halogeno ketones with primary amides (equation 122) is the Bliimlein-Lewy synthesis (1884/1888). The method succeeds best when the resulting oxazole contains one or more aryl substituents. The use of formamide leads to oxazoles with a free 2-position and in this case it is possible that the reaction proceeds as in equation (113). 2-Aminooxazoles are produced by the action of a-halogeno ketones on urea and its derivatives (equation 123) or on cyanamide (80ZOR2185). The mercury(II) sulfate-catalyzed condensation of alkynic alcohols or their esters with primary amides leads to trisubstituted oxazoles (equation 124). 

The chemistry and synthetic utility of cobalt complexed propargyl cations have been demonstrated by Nicholas in an impressive series of papers, and the area was reviewed in 1987.72 More recently, reviews of cluster-stabilized cations73 and propargylium complexes74 have appeared. Two general routes for the synthesis of dicobalt-propargylium complexes have been developed. The most commonly used method is the treatment of an alkynic ether or alkynic alcohol-hexacarbonyldicobalt complex with a Lewis or Bronsted acid [Eq. (7)]. 

Benzeneselenenyl chloride adds to alkynes to produce mixtures of trans-alkene adducts. For example, the addition of benzeneselenenyl chloride to the alkyne (18) produces the alkene (19), which can be transformed to yield the unusual diene (20 equation 16). Alkynic alcohols give anti-Miukovnikov addition products under kinetic control. The reaction is thought to proceed dirough the selenirenium ion (21 equation 17). Selenium electrophiles add to a, -alkynic caibonyl moieties to produce cis adducts in good yield (equation 18). ... 

Alkyne alcohols can be cyclocarbonylated to produce lactones (equation 29). A PdCl2/P(n-Bu)3/SnCl2 catalyst system has been shown to be quite efficient for this reaction at 75 °C and 8 bar CO pressure. ... 

One class of compounds that does not react particulariy well in activated dimethyl sulfoxide oxidations, however, is the alkynic alcohols, and only a few successful examples are known, e.g. (36) and (37). ... 

Cyclization of Divinyl Ketones from Alkynic Alcohols... 

Moving one step further back in the synthetic sequence towards cyclopentenoftes identifies the alkynic alcohols as viable precursors. Since the subsequent dehydration-hydration-cyclization steps are all acid-... 

A final class of oxy-Cope rearrangements leading to cyclodecenones is represented by spirodienol (120), which rearranges to a bicyclic ketone (121) containing a bridgehead double bond. ITie related alkynic alcohols (122) behave similarly, but when R is H the initial product imdergoes an intramolecular Michael addition to afford (123). 

Carbonylation reactions of organic compounds such as alkenes, alkynes, alcohols and amines are very important in organic synthesis. Ruthenium catalysts show unique catalytic activities in these reactions [2c]. 

Protonolysis can also be effected with weaker acids in some cases this may be essential. For example, hydrozirconation of alkynic alcohols Me(CH2)nC=C(CH2)mOH with 2 equiv. of (6), followed by hydrolysis with 2% aqueous NH4CI, affords the corresponding cis-alkenol in high yield and selectivity, whereas use of aqueous HCl causes both cis-trans isomerization and allylic rearrangement. Protonolysis by weak acid may be slow enough for other reactions to compete TBHP can be used as an oxidant (see below). 

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