Ammonium acetylid

Neutral alkynylcopper compounds are not prepared by transmetalation of alkynyllithium compounds. Rather, they are obtained by partially deprotonating terminal alkynes with amines and capturing the ammonium acetylide formed at equilibrium with Cul (—> R-C=C-Cu + R3NH I example Figure 16.7). Copper(I) cyanide couples with aryl iodides and -bromides in a similar fashion as alkynylcopper compounds (which may well be conceived as their carba analogs). 

Cacchi- and Sonogashira-Hagihara couplings occur only if a primary, secondary, or tertiary amine is present, and it is best to have the amine present in large excess. Under these conditions the acetylene will at least form a small equilibrium concentration of the corresponding ammonium acetylide or copper complex thereof. The copper iodide serves to trap this species as a copper acetylide. The copper acetylide represents a substantially improved nucleophile in comparison to the free acetylene. Without the Cul addition, the acetylide content of the reaction mixture is so small that a reaction occurs only at higher temperatures. 

Acetaldehyde—Acetic aldehyde—Acetyl hydrid——44 —is formed in all reactions in which alcohol is deprived of H without introduction of O. It is prepared by distilling from a capacious retort, connected with a well-cooled condenser, a mixture of HjSOj, 6 pts. HgO, 4 pts. alcohol, 4 pts. and pow dered manganese dioxid, G pts. The product is redistilled from calcium ehlorid below 50° (123° P.). The second distillate is mixed with two volumes of ether, cooled by a freezing mixture, and saturated with dry NHg there separate crystals of ammonium acetylid, CgHiO, NHi, -which are -washed with ether, dried, and decomposed in a distilling apparatus, over the water-bath, with tho proper quantity of dilute HjS04 the distillate is finally dried over calcium ehlorid and rectified below 35° (95° P.). 

Epichlorohydrin (1 mol) was added dropwise over a period of 1.5 h to a solution of 2.2 mol of sodium acetylide in 1.5 1 of liquid ammonia. During, as well as for a period of 1.5 h after, the addition the temperature of the mixture was kept at about -45°C. The cooling bath was removed after this period and the mixture was agitated vigorously for another 3 h. The thermometer and vent were removed, and 75 g of powdered ammonium chloride v/ere added in 2-g portions with vigorous stirring. The atimonia was allowed to evaporate. 

The enyne system in the amines 828=88-8 8-882 can be reversed by potassium amide in liquid ammonia. Addition of the enyne amines to an equivalent amount of this reagent gives the potassium acetylides, K-8e8-88=88-8R2, from which the ynene" amines can be obtained in excellent yields by addition of solid ammonium chloride. 

Hove 1. The procedure described in Ref. 1 was modified. To a solution of 2.0 mol of lithium acetylide in 1.2 1 of liquid ammonia in a 4-1 round-bottomed, three-necked flask (see Fig. 2) was added 1.5 mol of freshly distilled benzaldehyde with cooling at about -45°C. After an additional 30 min finely powdered ammonium chloride (2 mol) was introduced in 15 min. The ammonia was allowed to evaporate, then water (1.1 1) was added and the product was extracted with diethyl ether. After drying over magnesium sulfate the extract was concentrated in a water-pump vacuum. High-vacuum distillation,... 

Terminal alkynes are only reduced in the presence of proton donors, e.g. ammonium sulfate, because the acetylide anion does not take up further electrons. If, however, an internal C—C triple bond is to be hydrogenated without any reduction of terminal, it is advisable to add sodium amide to the alkyne solution Hrst. On catalytic hydrogenation the less hindered triple bonds are reduced first (N.A. Dobson, 1955, 1961). 

With stirring, 6 g of ammonium chloride (to decompose excess acetylide) is added and the remaining ammonia is allowed to evaporate. To the residue is added cautiously 50 g of crushed ice followed by 150 ml of water the contents are mixed and steam distilled rapidly to obtain the 1-hexyne. The organic layer is separated, dried (magnesium sulfate), and distilled through a short column. 1-Hexyne has bp 71-72° the yield is about 28 g (68 %). 

Methylsulfinyl carbanion (dimsyl ion) is prepared from 0.10 mole of sodium hydride in 50 ml of dimethyl sulfoxide under a nitrogen atmosphere as described in Chapter 10, Section III. The solution is diluted by the addition of 50 ml of dry THF and a small amount (1-10 mg) of triphenylmethane is added to act as an indicator. (The red color produced by triphenylmethyl carbanion is discharged when the dimsylsodium is consumed.) Acetylene (purified as described in Chapter 14, Section I) is introduced into the system with stirring through a gas inlet tube until the formation of sodium acetylide is complete, as indicated by disappearance of the red color. The gas inlet tube is replaced by a dropping funnel and a solution of 0.10 mole of the substrate in 20 ml of dry THF is added with stirring at room temperature over a period of about 1 hour. In the case of ethynylation of carbonyl compounds (given below), the solution is then cautiously treated with 6 g (0.11 mole) of ammonium chloride. The reaction mixture is then diluted with 500 ml of water, and the aqueous solution is extracted three times with 150-ml portions of ether. The ether solution is dried (sodium sulfate), the ether is removed (rotary evaporator), and the residue is fractionally distilled under reduced pressure to yield the ethynyl alcohol. 

Alone, or Metals, or Metal compounds Mellor, 1940, Vol. 8, 327 1967, Vol. 8, Suppl. 2.2, 84, 96 It is an explosive of positive oxygen balance, less stable than ammonium nitrate, and has been studied in detail. Stable on slow heating to 300°C, it decomposes explosively on rapid heating or under confinement. Presence of zinc, copper, most other metals and their acetylides, nitrides, oxides or sulfides cause flaming decomposition above the m.p. (70°C). Commercial cobalt (cubes) causes an explosion also. 

Several explosive salts including the acetylide, azide, borate, bromate, chlorate, chromate, iodate (and ammonium iodate double salt), nitrite, perchlorate (and ammonium perchlorate double salt), periodate, permanganate, picrate and trinitrobenzoate were prepared. The 3 latter salts and the acetylide, azide and bromate are impact-sensitive detonators [1], It appears probable that many of the explosively unstable compounds [2], formed in various ways from interaction of mercury or its compounds with ammonia or its salts, may have the common polymeric structure now recognised for Millon s base [3], This is a silica-like network of N+ and Hg in 4- and 2-coordination, respectively, with OH and water in the interstitial spaces. Individually indexed compounds are Poly(dimercuryimmonium acetylide)... 

Aluminium, 0048 Ammonium phosphinate, 4554 Barium phosphinate, 0210 f Benzaldehyde, 2731 1,4-Benzenediol, 2333 Bis(hydrazine)tin(II) chloride, 4070 Calcium acetylide, 0585 Calcium phosphinate, 3931 Chromium(II) chloride, 4052 Chromium(II) oxide, 4241 Chromium(II) sulfate, 4244 Copper(I) bromide, 0265 Diacetatotetraaquocobalt, 1780 Diisobutylaluminium hydride, 3082 f 1,2-Dimethylhydrazine, 0955... 

Formation of complex 26 by oxidation of the allenylidene-acetylide derivative 25 with cerium(IV) ammonium nitrate merits to be highlighted since 26 represents a unique example in which two allenylidene ligands are bonded to a metal (Scheme 10) [181]. 

Nitrogen halides are destroyed with cold base. Azides and fulminates-may often be destroyed with acid, while heavy metal acetylides are decomposed by ammonium sulfide. The removal of peroxides by reduction has been described above. 

---