Lithium diselenide

Trifluoromethyl thiirane is formed by the action of tris(diethylamino)-phosphineon l-chloromethyl-2,2,2-trifluoroethyldisulfide [S2] (equation 73) Difluoromethyl phenyl selenide is prepared by treatment of lithium phenyl-selemde with chlorodifluoroniethane via a carbene mechanism [Si] (equation 44) Bis(2,2,2-trifluoroethyl)diselenide is formed in the reaction of 2,2,2-trifluoroethyl mesylate with lithium diselenide [84] (equation 74). 

Lithium diselenide, Li2Se2 (1). This reagent is prepared conveniently by reaction of Se(0) with Li in THF at 20° with diphenylacetylene as electron carrier. 

Treatment of compound 174 with lithium ditelluride gave the heterocycle 175 in low yield (Equation 45) <2004EJO3857>. Analogous 1,2-selenazoles (derivatives of epselen) were prepared in a similar way by treatment with lithium diselenide (but in high yields) <2004EJO3857>. 

The parent 1,2-diselenolane and 4,4-dimethyl-1,2-diselenolane were prepared from the corresponding dibromo compounds and lithium diselenide in THF <88T6l 19>. l,2-Diselenolan-4-ol was synthesized from l,3-dibromopropan-2-ol and sodium hydrogenselenide <83AJC8i5>. 

Reduction with only 1 equiv. leads to the dark brownish-red lithium diselenide, which reacts with alkyl halides to form dialkyl diselenides (equation II). ... 

Lithiumboroethyrate also reacts with selenium (or tellurium) in THF to form lithium diselenide (or ditelluride) [209] ... 

Most of the other dichalcogenides are also electro-chemically active,and many show a similar singlephase behavior with lithium intercalation. Vanadium diselenide is an exception, showing two-phase be-... 

Vanadium diselenide also showed the feasibility of intercalating a second lithium into the lattice. The LiVSe2/Li2VSe2 system must be two phase, as the lithium in LiVSe2 is in octahedral coordination whereas in Li2VSe2 the lithium must move to tetrahedral coordination and both sites cannot be occupied at the same time. This two-lithium intercalation can be accomplished either electrochemically or chemically, for example, by using butyllithium. Other dilithium layered materials such as Li2Ni02 have also been formed both electrochemically and chemically... 

Figure 4. Electrochemical insertion of lithium into vanadium diselenide, showing reaction of two lithium (reprinted with permission from ref 61, copyright 1978 Elsevier) (top) open-circuit potentials, (bottom) behavior on cycling at 2 mA/cm. ...

By elimination reactions of selenides or selenoxides Diphenyl diselenide, 125 Hydrogen peroxide, 145 Other elimination reactions Chloromethyldiphenylsilane, 74 m-Chloroperbenzoic acid, 76 Hydrogen peroxide, 145 Iodomethyltrimethylsilane, 315 Lithium 4,4 -di-/-butylbiphenylide, 162... 

Ring opening of larger cyclic ethers such as tetrahydrofuran does not normally proceed with selenolates of type 77 generated from diselenides and sodium borohydride in alcohols. If diselenides are reduced with lithium aluminum hydride in tetrahydrofuran,171 or with sodium borohydride in the presence of aluminum trichloride,172 ring-opened products 89 are obtained (Scheme 20). 

The lithium alkyltelluroselenolates undergo internal redox reactions below room temperature to form dialkyl ditellurium and the diselenide anion. The phenyl derivative is stable under these conditions2. 

In aprotic solvents, such as dichloromethane and THF, potassium boro-hydride [10], lithium borohydride [8b], lithium triethylborohydride [8a, 11], and diisobutylaluminum hydride (DIBALH) [11] have been used instead of NaBH4. NaBH4 also reduces elemental selenium in alcohol or water to sodium hydrogen selenide or sodium diselenide (Na2Se2) depending on the stoichiometry of the reactants (Scheme 8) [12]. These anions are useful for the synthesis of selenides or diselenides, respectively, via nucleophilic substitution with various electrophiles. 

Compound 246 was prepared in a yield of 83% by treating lithium trimethylsilylacetylide with tellurium and carbon diselenide followed by water in the final step <2001JMC2431>. 

This type of deprotonation procedure can also be applied to prepare lithium or magnesium areneselenolates (143, 148) and sterically hindered silyltelluro-late derivatives of the Group 1 (1A) metals Li, Na, and K (149). An alternative procedure based on the reduction of a diselenide (RSeSeR) with [LiHBEt3] in THF can also afford the desired lithium areneselenolate (32). 

In the second method, the (l-selanylcyclopropyl)lithium reagent 2 is used to alkylate another a-selanyl aldehyde. Elimination, as above, of the resulting hydroxy diselenide 3 gives the alkenyl(selanyl)cyclopropane 4 with high selectivity for the E -isomer. The yields and isomer distributions of selenides 4 prepared by the two methods are indicated. These products can be converted to allylidene cyclopropanes by two cycles of alkylation and treatment with base (Section 5.2.2.4.). 

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