Acetylene, direct reaction with

Trichloromethyl lithium (generated from BrCCl3 and CH3Li at —100 °C) adds to dialkyl acetylenes and to monoalkyl acetylenes23, thus monoalkyl cyclopropenones became accessible which could not be obtained from terminal acetylenes by reaction with the above carbene sources. The 3,3-dihaIogeno-A1,2-cycIopropenes formed as primary products in the dihalocarbene reactions are usually not isolated, but are hydrolyzed directly to cyclopropenones. 

Trimethyllead hydroxides or methoxides, sometimes used in direct reactions with acetylenic derivatives for the preparation of alkynylplumbanes, are very suitable reagents176 ... 

The high acidity of the C-H bonds in acetylene compounds allows for the synthesis of alkali metal acetylene compounds by direct reaction with the metals. 

Scheme 44 outlines three new cycloaddition - type processes which lead to cyclic non-conjugated dienes. The synthesis of methylene cyclopentenes by direct reaction of a TMM with an acetylene proved unsuccessful. Masking the acetylene by reaction with cyclopentadiene allowed efficient TMM reaction, the final... 

Alkynyl anions are more stable = 22) than the more saturated alkyl or alkenyl anions (p/Tj = 40-45). They may be obtained directly from terminal acetylenes by treatment with strong base, e.g. sodium amide (pA, of NH 35). Frequently magnesium acetylides are made in proton-metal exchange reactions with more reactive Grignard reagents. Copper and mercury acetylides are formed directly from the corresponding metal acetates and acetylenes under neutral conditions (G.E. Coates, 1977 R.P. Houghton, 1979). 

Olefin and acetylene complexes of Au(I) can be prepared by direct iateraction of the unsaturated compounds with a Au(I) hahde (190,191). The resulting products, however, are not very stable and decompose at low temperatures. Reaction with Au(III) hahdes leads to halogenation of the unsaturated compound and formation of Au(I) complexes or polynuclear complexes with gold ia mixed oxidatioa states. 

The direct reaction of androsta-l,4-diene-3,17-dione with acetylene in the presence of potassium t-amyloxide gives the 17a-ethynyl-17j -hydroxyandros-ta-l,4-dien-3-one in only 12% yield. 

The Diels-Alder reaction of 2-vinylfurans 73 with suitable dienophiles has been used to prepare tetrahydrobenzofurans [73, 74] by an extra-annular addition these are useful precursors of substituted benzofurans (Scheme 2.29). In practice, the cycloadditions with acetylenic dienophiles give fully aromatic benzofurans directly, because the intermediate cycloadducts autoxidize during the reaction or in the isolation procedure. In the case of a reaction with nitro-substituted vinylbenzofuran, the formation of the aromatic products involves the loss of HNO2. 

The discovery that photolysis of hypochlorite (14) gave chloroketone (11) directly provided a short cut in this synthesis. The ketone in (11) will need to be protected during reaction with acetylene. 

As part of a study of the reactions of metallacyclic y-ketovinyl complexes of molybdenum and tungsten with acetylenes, directed toward the synthesis of complexed -/-lactones, Stone has reported92 the isolation of several vinyl-ketene complexes. When complex 72 was heated with 2-butyne, one molecule of the alkyne was incorporated into the complex with concomitant carbonylation. X-ray analysis of the product (73) has shown unequivocally that the C-l to C-4 vinylketene fragment is bonded in a planar, rj4-configu-ration. In contrast to the thermal reaction, ultraviolet irradiation of 72 or 74 in the presence of 2-butyne affords the complexes 75 and 76, respectively, where the lone carbonyl remaining after alkyne insertion had been replaced by a third molecule of the alkyne. 

Vinyl chloride is also produced by the direct chlorination of ethylene and the reaction of acetylene and hydrogen chloride (structure 17.29). The hydrogen chloride generated in the chlorination of ethylene can be employed in reaction with acetylene allowing a useful coupling of these two reactions (equation 17.30). 

Reaction with acetylenic dipolarophiles represents an efficient method for the preparation of 2,5-dUiydrothiophenes. These products can be either isolated or directly converted to thiophene derivatives by dehydration procedures. The most frequently used dipolarophile is dimethyl acetylenedicarboxylate (DMAD), which easily combines with thiocarbonyl yhdes generated by the extrusion of nitrogen from 2,5-dihydro-1,3,4-thiadiazoles (8,25,28,36,41,92,94,152). Other methods involve the desUylation (31,53,129) protocol as well as the reaction with 1,3-dithiohum-4-olates and l,3-thiazolium-4-olates (153-158). Cycloaddition of (5)-methylides formed by the N2-extmsion or desilylation method leads to stable 2,5-dUiydrothiophenes of type 98 and 99. In contrast, bicyclic cycloadducts of type 100 usually decompose to give thiophene (101) or pyridine derivatives (102) (Scheme 5.37). 

Dihydro allyl adducts like (254) are obtained by reaction of thiazoles with allyltributyl tin in the presence of alkyl chloroformates acting as activators of the thiazole ring (Scheme 28) (94JOC1319). This reaction most likely takes place via the intermediate azolium salt. Under these conditions even organolithium compounds can add to thiazoles (84TL3633). Similarly, direct ethynylation of thiazole and benzothiazole can be achieved by reaction with bis(tributylstannyl)acetylene (Scheme 29) (94SL557). 

Under the conditions of rapid heating used, the quantity of volatile matter might well have proved quite different from that obtained with slow rates of heating. Nevertheless, Figure 8 shows that the yield of acetylene under the present conditions is directly proportional to the standard volatile matter of the coal, irrespective of whether the coal consists mainly of vitrinite or spori-nite. This suggests that the acetylene is derived mainly from the coal volatiles rather than from complete volatilization of the coal. The small extent of reaction with Neospectra carbon black, and the soot itself when returned for further reaction, show that there is little volatilization of these materials even though they have a very small particle size. 

Pyridinium methylides react with alkynes such as DMAD, alkylpropiolates, cyano-acetylene and dicyanoacetylene to give indolizines (167) directly (Scheme 22). In most of the reactions with ethylenes, however, tetrahydroindolizines (168) and dihydroin-dolizines (169) and (170) are isolated as intermediates, which can be converted to indolizines in the presence of a dehydrogenating catalyst. 

Lithiation of imines and acetylene Imines and acetylenes can be lithiated directly by reaction with metallic lithium in THF at 10° with phenanthrene as the hydrogen acceptor (it is converted into 1,2,3,4,5,6,7,8-octahydrophenanthrene). 

Reactions of the recoil C1] with several olefins have been studied, including ethylene, propylene, cyclopentene, and cfs-butene-2, as well as with several paraffins. The type of products observed indicated the existence of several general modes of interaction, such as CH bond insertion, interactions with CC double bonds, formation of methylene-C11. The most important single product in all systems is acetylene, presumably formed by CH insertion and subsequent decomposition of the intermediate. Direct interaction with double bonds is shown by the fact that, for example, in the case of propylene, yields of stable carbon atom addition products were significantly higher than in the case of propane. The same was true for ethylene and ethane. 

Irradiation of ethyleneimine (341,342) with light of short wavelength in the gas phase has been carried out directly and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified in a fast flow photoreactor included hydrocyanic acid and acetonitrile (345), in addition to those found in a steady state system. The reaction of hydrogen radicals with ethyleneimine results in the formation of hydrocyanic acid in addition to methane (350). Important processes in the photolysis of ethyleneimine are nitrene extrusion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an intermediate in the photolytic formation of hydrocyanic acid from acetylene and ammonia in the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

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