4-pentyne-, sodium

Methyl-1-pentyne Sodium 4-methylpentynylide 5-Methyl-2-hexyne (81%)... 

Ketones react with acetylide ion (Section 8.7) to give alcohols. For example, the reaction of sodium acetylide with 2-butauone yields 3-methy -l-pentyn-3-ol ... 

Preparation of 4-pentyn-l-ol from 3-bromo-1-propanol and sodium acetylide ... 

The indanols 44 and 45 can only be the products of a formal [4 + 2] cycloaddition23 of the vinylketene complex 42.a with 1-pentyne. Note that upon reaction of 42.b with diethylpropynylamine a formal [2 + 2] cycloaddition65 is seen to take place, yielding the cyclobutenone 47 along with a tricarbonylchromium complex, tentatively identified as 48.66,67 As one would expect, the vinylketene complex 42.b underwent 1,2-additions with pyrrolidine and sodium methoxide in methanol, yielding 49 and 50, respectively. The CO-insertion step leading to vinylketene formation is reversible in some systems,51,68,69 but there is no evidence of this for complex 42.a. Heating a benzene solution of complex 42.a at 80°C under an atmosphere... 

A solution of 2.5 mol of sodium acetylidc in liquid NHj (p. 17-19) is cooled to —40 C and a vigorous stream of acetylene is introduced for 2 min (31/mjn). The alkyl bromide (2.0 mol) is then added dropwise over 1 h while maintaining the temperature as close as possible to -38 C Stirring at this temperature is continued for another 1.5 h (for the type of stirrer see fig 3), then 300 ml of high-boiling petroleum ether (b.p. >170 C) is added. The mixture is cautiously poured onto 2 kg of finely crushed ice in a 5-1 wide-necked round-bottomed (fig. 13) or conical flask. The reaction flask is rinsed with a small amount of ice water which is added to the bulk. After separation of the layers, three extractions with small amounts of petroleum ether are carried out The extracts are washed with dilute hydrochloric acid and subsequently dried over MgS04. Isolation is carried out as described in exps. 1 and 3, and in Chap. 1-2.6. The product is carefully redistilled through a 40-cm Widmer column. 1-Pentyne, b.p. 

In the preparation of 1-pentyne and 1-hexyne (exp. 10) complete conversion of the alkyl bromides is effected by using an excess of sodium acetylide. A reasoning based on economics prompts the use of an excess of the alkyl halide if alkali vinylacetylide or alkali diacetylide (generated from alkali amide and dichlorobutene or dichlorobutyne, respectively) are to be alkylated. If slightly mare than the stoichiometiical amount of alkyl bromide is used, no serious separation problems will be encountered during the final distillation. A relatively small amount of DMSO is added to enhance the solubility of the alkyl bromides, thereby facilitating the alkylation reaction. 

To a flask containing 20.0 gm (0.061 mole) of l-bromo-l,l-diphenyl-4,4-dimethyl-2-pentyne, 500 ml of dry ether, and 50 ml of 40 % sodium amalgam, the air is displaced by nitrogen, the flask is stoppered, and then placed in a mechanical shaker for 48 hr. The flask is cooled, and previously boiled water is slowly added to discharge the red color. Approximately 200 ml of water is added, the ether layer separated, washed with water, dried, concentrated,... 

SYNS 5-ALLYL-l-METHYL-5-(l-METHY1 2-PENTYN-YL)BARBITURIC ACID SODIUM SALT BREVIMYTAL BREVITAL SODIUM BRIETAL SODIUM ENALLYNYMAL SODIUM ULLY 22451 METHO-HEXITONE SODIUM l-METHYL-5-ALLYL-5-(l-METHYL-2-PENTYNYL)BARBITURIC ACID SODIUM SALT SODIUM-dl-5-ALLYL-l-METHYL-5-(l-METHYL-2-PENTYNYL)BARBITURATE SODIUM METHOHEXITAL SODIUM METHOHEXITONE SODIUM dl-l-METHYL-5-ALLYL-5-(l-METHYL-2-PENTYNYL)-BARBITURATE... 

Pentyne and 1-hexyne are hydrogenated with [Ti(Cp)2(CO)2] to 1-pentene and 1-hexene, respectively, but phenylacetylene gives ethylbenzene. Reduced compounds of [Ti(Cp)2Cl2] with Na, Mg, Ca, sodium naphthalenide, or butyllithium catalyze the hydrogenation of a variety of alkynes to alkenes. 

Grignardization of 1-butynyl magnesium bromide with acetaldehyde and subsequent treatment of the resulting alcohol with PCI5 yields 2-chloro-3-pentyne. Now, ethyl (l-methyl-2-pentynyl)-eyanoaeetate is obtained therefrom by its condensation with ethyl cyanoacetate in the presence of sodium ethylate. Further condensation of the resulting produet with allyl bromide gives rise to ethyl-(l-methyl-2-pentynyl) allylcyanoaeetate. Condensation with N-methyl urea and subsequent neutralization with NaOH produees methohexital sodium. 

Suppose, for example, we wanted to prepare 4-pentyn-l-ol from 3-bromo-1-propanol and sodium acetylide. If we allow them to react directly, the strongly basic sodium acetylide will react first with the hydroxyl group, making the alkylation unsuccessfiil ... 

Draw the radical anion formed when 1,3-diphenyl-l-pentyne is treated with sodium metal in liquid ammonia and ethanol and then draw the final product of this reaction. 

This synthesis can be done in two steps Treating 1-pentene with 1 mole of bromine gives 1,2-dibromopentane. Treating this dibromoalkane with 3 moles of sodium amide followed by H O gives 1-pentyne. 

We can use a silyl ether in the following way to convert 4-pentyn-l-ol to 4-heptyn-l-ol. Treating 4-pentyn-l-ol with chlorotrimethylsilane in the presence of triethylamine gives the trimethylsilyl ether. Treatment of the terminal alkyne with sodium amide followed by bromoethane forms the new carbon-carbon bond. 

When 3,3-dichloropentane is treated with excess sodium amide in liquid ammonia, the initial product is 2-pentyne ... 

Imagine that a reaction similar to that in Problem 5.76 is carried out between sodium acetylide and (J )-2-phenylpropanal to yield 4-phenyl-l-pentyn-3-ol ... 

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