Selenium reactions with acetylene

Reactions of acetylene derivs. with selenium monochloride 3-Chlorobenzo[b]selenophenes... 

Reaction of Sodium Acetylide in Liquid Ammonia with Selenium and Subsequent Ethylation. Formation of Bis(ethylseleno)acetylene... 

Umezawa et a/.128,129 analyzed the residue formed in the reaction of acetylene with selenium and isolated three selenophenoselenophene isomers selenopheno [ 2,3-A] selenophene (11), selenopheno[ 3,2-b]-... 

A powerful oxidizer. Explosive reaction with acetaldehyde, acetic acid + heat, acetic anhydride + heat, benzaldehyde, benzene, benzylthylaniUne, butyraldehyde, 1,3-dimethylhexahydropyrimidone, diethyl ether, ethylacetate, isopropylacetate, methyl dioxane, pelargonic acid, pentyl acetate, phosphoms + heat, propionaldehyde, and other organic materials or solvents. Forms a friction- and heat-sensitive explosive mixture with potassium hexacyanoferrate. Ignites on contact with alcohols, acetic anhydride + tetrahydronaphthalene, acetone, butanol, chromium(II) sulfide, cyclohexanol, dimethyl formamide, ethanol, ethylene glycol, methanol, 2-propanol, pyridine. Violent reaction with acetic anhydride + 3-methylphenol (above 75°C), acetylene, bromine pentafluoride, glycerol, hexamethylphosphoramide, peroxyformic acid, selenium, sodium amide. Incandescent reaction with alkali metals (e.g., sodium, potassium), ammonia, arsenic, butyric acid (above 100°C), chlorine trifluoride, hydrogen sulfide + heat, sodium + heat, and sulfur. Incompatible with N,N-dimethylformamide. 

ACETYLENOGEN (75-20-7) Contact with water, moist air, steam, alcohols forms explosive acetylene gas, corrosive calcium hydroxide, and heat. Violent reaction with acid, acid fumes, copper salts, strong oxidizers (bromine, chlorine, iodine, etc.), iron trichloride, tin dichloride, silver nitrate. Incompatible with oxidizers, hydrogen chloride, methanol, copper salt solutions, lead fluoride, magnesium, selenium, sodium peroxide, stannous chloride, sulfur. 

The increasing reactivity with alkyl substitution in the acetylenes is very pronounced something in excess of a factor of 100 in relative rates at 298°K. This, it may be observed, is substantially greater than the factor of 20 between the reactivities of ethylene and 2-butene. Such large relative reactivity differences are rare in free radical reactions, and one realizes that the triplet sulphur atom must be very selective in its reaction with different olefins. A comparison of the behaviour of the triplet state atoms of oxygen, sulphur and selenium will be deferred until the end of the discussion of this whole group of atom additions. 

Lie Ken Jie, M.S.F., M.K. Pasha, and M.S. Alam, Oxidation Reactions of Acetylenic Fatty Esters with Selenium Dioxide/tert-Butyl Hydroperoxide, Lipids 32 1119-1123 (1997). 

Selenophene itself is commercially available, but is fairly expensive. It can be conveniently obtained in 70% yield via a one-step thermal reaction between selenium and acetylene at 450 °C (Scheme 6.1) unfortunately, this pyrolytic reaction requires a troublesome gas-flow system equipped with an electric furnace, thus hindering the large-scale production of selenophene [17]. The conventional electrophilic substitution reactions of selenophene, like thiophene, can provide its substituted derivatives, but the yields are generally lower compared with those of similar reactions of thiophene [32]. Moreover, the conversions... 

Benzoselenophene [111, 112] and related fused selenophenes [113-116] were previously obtained via tedious multistep reactions involving a selenocyclization reaction from barely accessible selenium-containing compounds. Such conventional synthetic methods are unsuitable for the development of selenophene-based OFET materials. Sashida s group developed a simple one-pot preparation of benzoselenophenes by an intramolecular selenocyclization reaction of acetylene compounds with a selenolate anion [117, 118]. This allowed straightforward access to sophisticated fused selenophenes, such as 52 and 53, from commercially available chemicals [119, 120]. Scheme 6.9 depicts the key selenocyclization reaction used in the synthesis of 52. This synthetic protocol was also successfully applied to the synthesis of regioisomer 54 [121]. 

Sulphenyl Halides.— Illustrative procedures for the synthesis of sulphenyl halides reported during the period under review employ well-established methods, Tetrachloropyridine-4-sulphenyl chloride is obtained from the corresponding disulphide by chlorinolysis, while the corresponding sulphonyl chloride is formed in AcOH or hydroxylic media. 2-Methyl-2-propanesulphenyl iodide is obtained from the thiol with la, or from the sulphenamide with HI addition reactions of selenium dichloride, or seleninyl chloride, to acetylene are specific examples of generally applicable reactions - (HC=CH + SeCU C1CH=CH-Se-Cl). The chlorination of CSa under activated charcoal catalysis has been developed as a continuous process, giving trichloromethanesulphenyl chloride. 

Epoxidation of f-butyldimethylsilyl-l-(ethoxyethoxy)allene (6) with /n-chloroperbenzoic acid leads to an a-keto acylsilane, presumably through an allene oxide intermediate (eq 6). Deprotonation of (6) at C-3 and trapping of the anion with selenium, followed by iodomethane, produces an aUenyl selenide. The reaction of this material with peracid follows a different course, leading to an acetylenic acylsilane, presumably via [2,3]-sigmatropic rearrangement of an allenyl selenide (eq 6) ... 

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