Selenides, propargyl phenyl

Propargyl phenyl selenide is a versatile multifunctional acrylate synthon, as shown in Scheme 12. The (Uanion is prepared and reacted successively with an alkylating agent (R— X) and an electrophile (E ). The oxidative rearrangement of the propargylic selenoxide (35) to an allenic selenenate (36), and thence to the a-phenylselenoenone (37), forms the keystone of this synthetic method, and ovendl yields firom propargyl phenyl selenide are in the range of 38-68%. Further elaboration of (37) is possible... 

Dibromoselenuranes 196 can be prepared from the corresponding selenides by reaction with elemental bromine. The a,/ -unsaturated ester 196 is converted into the a-bromo-/ ,7-unsaturated ester 197 by elimination of phenyl-selenenyl bromide (Scheme 58).338 Dibromoselenuranes from propargylic selenides undergo similar reactions leading to either allenes or propargylic bromides.339... 

Decomposition of dihalogenoselenuranes 167, derived from propargylic selenides, resulted in the formation of 1,3-substituted l,3-dihalo-2-phenyl-selenopropanes 168 and 169 as well as 1-substituted 1,2,3-trihalopropanes 170 and 171 as shown in Scheme 21 177]. 

Phenyl propargyl sulfide " and selenide are rapidly deprotonated by 2 equiv. of base. The resulting dilithio derivatives react at their allylic rather than at their alkynic carbon centers (Scheme 34, entries c and d). Reduction of the sulfides allows the synthesis of 1,5-enynes (Scheme 34, entry b), whereas oxidation of the selenides leads to a-phenylseleno-a,P-unsaturated carbonyl compounds (Scheme 34, entry... 

Propargyl selenides, such as phenyl propargyl selenide, are readily deprotonated by LDA at -78 °C to give a stable dilithium reagent which is of synthetic value in preparing disubstituted propargyl selenides. 

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