Selenocyanates oxidation

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

Diphenyl diselenide has been prepared by disproportionation of phenyl selenocyanate in the presence of potassium hydroxide" or ammonia/ and by air oxidation of benzeneselenol. The preparation of benzeneselenol is described in an earlier volume in this series/ In the present procedure phenylselenomagnesium bromide formed from phenylmagnesium bromide and selenium is oxidized directly to diphenyl diselenide with bromine/ Thus the liberation of the malodorous and toxic hydrogen selenide and benzeneselenol is avoided. Benzeneselenenyl chloride has been prepared by thermal elimination of ethyl chloride from ethyl phenyl selenide di-chloride/ by thermal elimination of chlorine from phenylselenium trichloride," and by chlorinolysis of diphenyl diselenide with either sulfuryl chloride " or chlorine. " ... 

The carbon-nitrogen triple bond of aryl thiocyanates acts as a dipolarophile in 1,3-dipolar cycloadditions. Reactions with nitrile oxides yield 5-arylthio-1,2,4-oxadiazoles 227 (X = O Y = S). Aryl selenocyanates behave similarly forming 5-arylseleno-l,2,4-oxadiazoles 227 (X = 0 Y = Se). Reactions of 5-aryl-... 

Olefin synthesis from the 5yn-oxidative elimination of o-nitrophenyl selenides, which may be prepared using o-nitrophenyl selenocyanate and BU3P, among other methods. 

Cyanogen Triselenide, Se3(CN)2, may be prepared by the action of a current of chlorine diluted with air on an aqueous solution of potassium selenocyanate, KCNSe. It may also be advantageously obtained by the action of nitric oxide on a paste of potassium selenocyanate with water. 

Magnesium Selenocyanate, Mg(CNSe)2, has been prepared by dissolving magnesium oxide in selenocyanic acid. On evaporation the salt is obtained as a gummy mass, apparently devoid of crystalline structure.2... 

Zinc Selenocyanate may be obtained by dissolving either the metal or its oxide in selenocyanie acid. It forms groups of prismatic needles, which are not deliquescent.4 By the action of selenium on a solution of zinc cyanide in liquid ammonia, the compound Zn(CNSe)a. 4NIT8 has been obtained.5 Similar compounds of magnesium and aluminium have also been described. 

Complexes with pyridine JV-oxide of zinc thiocyanate and selenocyanate of the stoichiometry ZnLsX2 (X = SCN, SeCN) have been reported.1066 IR evidence shows that they are best formulated as [ZnL6]2+[ZnX4f. ... 

Selenocyanates are transformed by alkali to selenides (seleno-mercaptans), the oxidation of these products yielding diselenides, an example being as follows ... 

It has already been pointed out that this compound may be prepared by hydrolysis of the selenocyanate it may also be obtained by the interaction of sodium selenide and 1-chloroanthraquinone. By the latter process orange-red plates, M.pt. 212° C., result. If 2-chloroanthra-quinone be used in the reaction, 2-anihraquinone selenophenol is obtained as an orange-yellow product, which gives a violet-red solution in sulphuric acid. Concentrated nitric acid causes oxidation to the seleninic acid. 

The selenium linker 1.45 (103), obtained from Merrifield resin and potassium selenocyanate, was treated according to oxyselenylation conditions to give a supported selenolactone. Oxidative deseleny lation (m-CPB A, DCM, rt) produced the unsaturated lactone in good yield and purity. An expansion of this chemistry, including several SP transformations prior to the cleavage, is mentioned in the original paper (103). 

Cyclizations by formation of carbon—selenium bonds represent a modern method with a high synthetic potential in the chemistry of cyclophanes. Selenocyanates such as 16 are accessible usually in excellent yields through the reaction of bromides with KSeCN [27], The reaction with benzylic bromides under reductive conditions using the dilution principle results in good to excellent yields of [3.3]di-selenacyclophanes which can be deselenized photochemically, pyrolytically (without previous oxidation), or by reaction with arynes, Stevens rearrangement and subsequent reaction with Raney nickel. [2.2]Metacyclophane (18), for example, is accessible in 47% total yield by using this sequence of reactions starting with... 

Reaction of alcohol 4.12 with o-nitrophenyl selenocyanate (4.13) and tributylphosphine gives 4.14. Oxidation of 4.14 with hydrogen peroxide gives selenoxide 4.15. Aryl selenoxide 4.15 bearing a (3-hydrogen atom is unstable and undergoes thermal syn-elimination to give styrene (4.16) with the expulsion of a selenol 4.17 in a fashion similar to that of the Cope elimination (Scheme 4.13). 

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