Phosphorus pentaselenide

Another method, due to V an Dormael (57) involves heating acelamidoethanoi with phosphorus pentaselenide (Scheme 57),... 

Phosphorus pentaselenide prepared from red, amorphous selenium effects cyclization of 1,4-diketones (22) to substituted selenophenes (23) in moderate... 

Phosphorus pentaselenide, obtained by heating together an intimate mixture of selenium and red phosphorus, when warmed with water gives a steady stream of hydrogen selenide.4... 

Phosphorus Pentaselenide or Phosphoric Selenide, P2Se5, may be prepared3 by melting together phosphorus and selenium in the atomic proportions until combination takes place. 

Selenophosphates and Oxyselenophosphates.—By the action of phosphorus pentaselenide on aqueous solutions of the selenides of... 

The oxyselenophosphates may also be prepared by the action of phosphorus pentaselenide on the hydroxides of the metals. Normal salts are only obtained in the case of the alkali metals the alkaline earth metals give monohydrogen salts. The following oxyselenophosphates have been prepared and described 1... 

Sodium Triowyselenophosphate, Na3PSeO3.20H2O, obtained by the action of phosphorus pentaselenide on either sodium hydroxide or sodium hydroselenide, crystallises in needles. 

Barium Dioxydiselenophosphate, BaHPSe202.14H20, formed when phosphorus pentaselenide is treated either with a solution of barium hydroxide or with a saturated solution of hydrogen selenide in barium hydroxide, is a white, microerystalline powder. 

Calcium Oxyselenophosphate has been obtained in the same way, using calcium hydroxide instead of strontium hydroxide. With the smaller proportion of phosphorus pentaselenide the crystals have the composition CaHPSejk0y.5lI20, whilst with the larger proportion their composition is CaHPSeOs.8H20. 

The original synthesis of 2,5-disubstituted selenophenes from 1,4-diketones and phosphorus pentaselenide (1885CB2255) has been greatly improved by the introduction of a method of producing phosphorus pentaselenide from red amorphous selenium (77CS(12)ll). 

Tetrabenzoylethane (315) and freshly prepared phosphorus pentaselenide were reacted in both pyridine and xylene as solvents. In either case, only the reduced selenides (316) (cis/trans) were formed, along with minor amounts of the substituted selenophenes (317) and (318 Scheme 109) (77CS(l2)li). 

Phosphorus pentaselenide is heated with a mixture of concentrated potassium or sodium hydroxide and potassium alkyl sulphate, the resulting product being fractionated ... 

Phosphorus pentaselenide, 24 grams, is boiled with 23 grams of powdered selenium in an aqueous alcohol solution of sodium hydroxide for two to three hours. To the resulting solution 39 grams of p-chloronitro-benzene in hot alcohol are added and boiling continued for a further two hours. The precipitate which forms is washed with water and extracted with boiling ethyl acetate. The selenide melts at 170° to 171° C.7... 

Selenodiazoles are prepared by the interaction of sz/m.-diacetyl- or dibenzoyl-hydrazines and phosphorus pentaselenide, or by treating arylselenamides with iodine in alcohol solution. The formulas proposed for these compounds are... 

Diphenyl-EGaAS -dithia-O-selenapentalene has been prepared by two different methods (a) reaction of phosphorus pentaselenide with2-phenyl-(5-phenyl-l,2-dithiol-3-ylidene)ethanal86 and (b) reaction of sodium hydrogen selenide with the Vilsmeier salt (70).49... 

Phosphorus pentasulfide has often been used for converting an O—S—S sequence into an S—S—S one <71AHC(13)161,p. 192,77AG(E)403,80JOC3909). Similarly, an O—S—O sequence can be transformed into an O—S—S one and an O—Se—Se sequence into an S—Se—Se one. All these reactions involve an attack at position 2 by a nucleophilic sulfur atom, while the oxygen atom in position 1 is removed by fixation on phosphorus. In the same way, phosphorus pentaselenide converts O—S—S sequences into Se—S—S ones. 

Selenophene (C4H4Se) is a five-membered heterocyclic compound containing one heteroatom. The first compound of this series to be prepared was 2,5-dimethylselenophene, obtained in 1885 by Paal1 from acetonylacetone by heating it with phosphorus pentaselenide. Unsubstituted selenophene was obtained much later it was mentioned... 

Disubstituted-l,3,4-selenadiazoles (174) were obtained by Stolle and Gutmann in 1904, through the reaction of iV,iV -diacylhydrazines (173) with phosphorus pentaselenide. [Eq. (45)]. 

The chemistry of selenazoles is reviewed in a book <04MI777>. Addition of malonic dinitrile with phosphorus pentaselenide in aqueous ethanol affords selenomalonic diamide 282, which undergoes double cyclization with phenacyl bromide to furnish bis(selenazole) 283 <04S875>. 2-Acyl-l,3-selenazoles 287 are prepared in two steps from bromomethyl ketones 284 and selenoamides 285. A facile preparation of l,3-selenazole-5-carboxylic acids 289 is based on the cyclization of selenazadienes 288 with chloroacetyl chloride <048233>. 

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