Preparation of acetylene

Fig 23(A) shows an assembly for boiling a liquid under reflux whilst adding another liquid at a rate which can be clearly seen cf. preparation of acetophenone, p. 253). The outlet A allows expansion of the vapour content, and can be fitted with a calcium chloride or soda-lime tube. The outlet A can also be used for collecting a gas evolved during the reaction cf, preparation of acetylene,... 

To a mixture of O.BB mol of anhydrous lithium chloride and 100 ml of OMSO was added a solution of 0.40 mol of the acetylenic tosylate (for a general procedure concerning the preparation of acetylenic tosylates, see Chapter VllI-3, Exp. 3) in IBO ml of DMSO. The flask was equipped for vacuum distillation (see Fig. 5). Between the receiver, which was cooled at -75°C, and the water-pump was placed a tube filled with KOH pellets. The apparatus was evacuated (10-20 mmHg) and the flask gradually heated until DMSO began to reflux in the column. The contents of... 

Equations 37 and 38 show a convenient procedure for the preparation of acetylenes and polyenes which utilizes an excess of f-BuOK as a base in THF or THF-f-BuOH. 

The N-aminoaziridine version7 of the a,/3-epoxyketone->alkynone fragmentation is a possible alternative in situations where the simple tosylhydrazone version6-9 fails. The tosylhydrazone method often gives good yields at low reaction temperatures, but it tends to be unsuccessful with the epoxides of enones that are not cyclic or are not fully substituted at the /5-carbon atom. For example, it has been reported9 that 2,3-epoxycyclohexanone docs not produce 5-hexynal by the tosylhydrazone route. The A-aminoaziridine method can also be recommended for the preparation of acetylenic aldehydes as well as ketones. 

It occurs with the alkyls, aryls or acetylides of metals more electropositive than magnesium, but including Grignard reagents, and is often carried out by adding a solution of the organometallic compound in an inert solvent to a large excess of powdered, solid C02 it is a particularly useful method for the preparation of acetylenic acids. The Kolbe-Schmidt reaction (p. 291) is another example of carbanion carbonation. 

The preparation of acetylenic ketones from soluble silver acetylenides and acid chlorides was reported in 1956 (Scheme 108).512 Analogously to that report, the reaction of silver acetylenides with acylpyridinium salts was reported to proceed effectively.513 This chemistry was applied to the synthesis of cotarnine derivatives, as exemplified in Scheme lQ9.514 514a... 

Much early effort in 5-LO inhibition centered on substrate and product analogues. One goal, especially of the Corey group at Harvard, was to study the 5-LO reaction by creating mechanism-based irreversible inhibitors, or by removing the substrate protons which are abstracted by the enzyme. These approaches, which included preparation of acetylenic, methylated, cyclized, or thia-analogues of arachidonic acid, and cyclopropyl analogues... 

Preparation of Acetylenic Acetals from ADsynylmagnesium Bromide and... 

Miscellaneous Preparations of Acetylenic Deri vatives 1. Halogen Compounds, Sulfinates, Sulfonates and Acetates All temperatures are internal, unless indicated otherwise... 

J. Klein, "Propargylic Metallahon" D.A. Ben Efraim, "The Preparation of Acetylenes and their Protection" P.F. Huldrik, A.M. Huldrik, "Applications of Acetylenes in Organic Synthesis" F. Thdron, M. Veraey, R. Vessiere, "Rearrangements Involving Acetylenes" W.D. Huntsman, "Synthetic Acyclic... 

Another method for the preparation of acetylenic carboxylates involves the reaction of 1-alkenylboranes with CO and alcohols (equation 135). The alkenyl boranes are readily prepared from alkynes by addition of boranes. PdCl2 was again the catalyst, with NaOAc as base and benzoquinone as oxidant.541... 

Having established that the end game of the proposed synthesis of cylindrospermopsin (1) from bromoketone 4 was viable, we turned our attention to the preparation of acetylene 5 from 4-methoxy-3-methylpyridine (7). 4-Methoxy-3-methylpyridine (7) was prepared by modifications of the literature procedure.17,18 3-Methyl-4-nitropyridine A-oxide (27),19 was treated with K2CO3 in methanol at 70 °C to displace the nitro group to... 

Bowden, K., I. M. Heilbron, E. R. H. Jones, and B. C. L. Weedon (1946) Researches on acetylenic compounds. Part I. The preparation of acetylenic ketones by oxidation of acetylenic carbinols and glycols. Journal of the Chemical Society (London), 39-45. 

How to Use the Book to Locate Examples of the Preparation or Protection of Monofunctional Compounds. Examples of the preparation of one functional group from another are located via the monofunctional index on p. xiii, which lists the corresponding section and page. Thus Section 1 contains examples of the preparation of acetylenes from other acetylenes Section 2, acetylenes from carboxylic acids and so forth. 

Examples of alkylation, dealkylation, homologation, isomerization, and transposition are found in Sections 1, 17, 33, and so on, lying close to a diagonal of the index. These sections correspond to such topics as the preparation of acetylenes from acetylenes carboxylic acids from carboxylic acids and alcohols, thiols, and phenols from alcohols, thiols, and phenols. Alkylations that involve conjugate additions across a double bond are found in Section 74 (alkyls, methylenes, and aryls from olefins). 

J. Chatt, and L. A. Duncanson, Infrared Spectra and Structure Attempted Preparation of Acetylene Complexes, J. Chem. Soc. 1953, 2939-2947. 

Another procedure for the preparation of acetylenes 8 and 9 is the cleavage of substituted... 

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. ... 

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