Isopropenyl acetylene

It is shown in exp. 27 that lithium acetylides do not react at room temperature with oxirane in a THF-hexane mixture. In contrast, the allylic pan of dilithiated isopropenyl-acetylene is smoothly hydraxyethylated at temperatures in the region of -50 C. 

The procedure of exp. 12 exemplifies the regiospecific reaction of dilithiated isopropenyl acetylene with carbonyl compounds. This example is significant in that the coupling product is a precursor of an aggregation pheromone of the baric beetle treatment with activated zinc powder in ethanol gives ipsenol H2C=CHC(=CH2)CH2CH(OH)CH(CH3)2 in almost quantitative yield. [46]... 

Formation of alkyne dimers with a GO inserted was observed in the thermal reactions of Fe3(GO)i2 with isopropenyl-acetylene two isomeric open clusters 3a and 3b were isolated and characterized by X-ray diffraction. In contrast, the thermal reactions of internal propargylic alcohols with Fe3(GO)i2 led to pentanuclear acetylide derivatives, obtained upon elimination of aldehydes or chetones from the alkynes (Figure 1). ... 

In the flask were placed 1.50 mol of the isopropenyl ether (conmercially available) and 0.10 mol of the (dry) acetylenic alcohol (also commercially available), and in the dropping funnel 0.4 mol of the latter compound. The mixture was cooled to 0°C and 100 mg of anhydrous p-toluenesulfonic acid were added with stirring. 

Industrial synthesis of nerolidol starts with linalool, which is converted into ger-anylacetone by using diketene, ethyl acetoacetate, or isopropenyl methyl ether, analogous to the synthesis of 6-methyl-5-hepten-2-one from 2-methyl-3-buten-2-ol. Addition of acetylene and partial hydrogenation of the resultant dehydroner-olidol produces a mixture of cis- and trans-nerolidol racemates. 

Many such activated acyl derivatives have been developed, and the field has been reviewed [7-9]. The most commonly used irreversible acyl donors are various types of vinyl esters. During the acylation of the enzyme, vinyl alcohols are liberated, which rapidly tautomerize to non-nucleophilic carbonyl compounds (Scheme 4.5). The acyl-enzyme then reacts with the racemic nucleophile (e.g., an alcohol or amine). Many vinyl esters and isopropenyl acetate are commercially available, and others can be made from vinyl and isopropenyl acetate by Lewis acid- or palladium-catalyzed reactions with acids [10-12] or from transition metal-catalyzed additions to acetylenes [13-15]. If ethoxyacetylene is used in such reactions, R1 in the resulting acyl donor will be OEt (Scheme 4.5), and hence the end product from the acyl donor leaving group will be the innocuous ethyl acetate [16]. Other frequently used acylation agents that act as more or less irreversible acyl donors are the easily prepared 2,2,2-trifluoro- and 2,2,2-trichloro-ethyl esters [17-23]. Less frequently used are oxime esters and cyanomethyl ester [7]. S-ethyl thioesters such as the thiooctanoate has also been used, and here the ethanethiol formed is allowed to evaporate to displace the equilibrium [24, 25]. Some anhydrides can also serve as irreversible acyl donors. 

Synthesis of fi-ketoallenes and a,fi-unsaturated ketones.1 Isopropenyl methyl ether, under acid catalysis (p-toluenesulfonic acid or phosphoric acid particularly), reacts with a tertiary acetylenic carbinol to give a/3-ketoallene in high yield, as exemplified by the reaction with 3 methylbutyne-l-ol-3 (1). The /3-ketoallene (2) is... 

The selective synthesis of pseudoionone is achieved by the acetylenic oxy-Cope rearrangement of 4-isopropenyl-3,7-dimethyl-6-octen-l-yn-3-ol (37) in A-methylpyrrolidone (NMP) as solvent containing a trace of hydrobromic acid, or iodine772,1127. 

Tertiary acetylenic alcohols react with isopropenyl ethers in the presence of a small amount of acid to yield 2-oxoalkyl allenes 9... 

The hydroxyketone, protected with isopropenyl methyl ether, (73) is coupled to the protected C6-lithium acetylenide 80. The Cj -triol 87 is formed after removal of the protecting groups. Acid-catalysed dehydration of 87 leads to the Ci5-diol 88, which is partially produced in the (9Z)-form. The (9 )-compound must be isolated by crystallization from the ( 7Z)-mixture of the acetylenic Cis-phosphonium chloride 89 prepared in the conventional manner. Successive partial hydrogenation of (E)-89, palladium-catalysed isomerization, and crystallization, give 86 in an overall yield of 43% based on 73. 

Rostami-Charati and Hossaini reported the multicomponent synthesis of phosphonates on water by the reaction of activated acetylenes 143, 4-hydroxycoumarin/l-(6-hydroxy-2-isopropenyl-1 -benzofuran-yl)-1 -ethanone (142), and trialkylphosphites 144 [78], The reaction mixtures were heated at 70°C to render the corresponding phosphate derivatives 145 in good yields (Scheme 11.29). 

As shown in Scheme 1.46, a simple synthesis of complex fused 1,4-benzoxaz-epin-2-one derivatives 86 and 87 was aehieved via a three-component leaction of quinoline or isoquinoline, acetylene dicaiboxylic esters and l-(6-hydioxy-2-isopio-penyl-l-benzofman-yl)-l-ethanone in water, in the absence of aiy catalyst [68]. Presumably, this transformation proceeds via the initial formation of a 1 1 zwitter-ionic intermediate 88 from the Michael addition of isoquinohne (or quinolone) to the activated ester. A proton transfer reaction takes then place in which this species is protonatedby the phenol group in the l-(6-hydroxy-2-isopropenyl-l-benzofuran-yl)-l-ethanone substrate, and this is followed by a second Michael addition of the resulting phenoxide anion to the isoquinohnium ion to afford intermediate 88, containing benzofuryl and isoquinoline ring systems. This intermediate then undergoes... 

Ethylene, butene-1, isobutene, acetylene, CO2, CH4, CO, acetone, isopropylaldehyde, methacrolein, butyraldehyde, methyl ethyl ketone, benzene (trace), methyl isopropyl ketones, methyl isopropenyl ketone, diethyl ketone, methyl n-propenyl ketone, cyclopentanone, methyl... 

Stable derivatives of diallgrl 2-(dialko3g hosphoryl)succinates (250) and (252) have been prepared in water, in good yields using multicomponent reactions involving activated acetylenic compounds (249), trimethyl phosphite or triphenyl phosphate, l-(6-hydro3y-2-isopropenyl-l-benzo-furan-yl)-l-ethanone (248) or 4-hydro3Q coumarin (251) (Scheme 89). °... 

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