Selenides nickel boride

Reductive deseleneniation.1 Aryl selenides and selenoketals can be reduced efficiently by nickel boride, generated in situ from NiCl2-6H20 and NaBH4. Selective deseleneniation is possible in the presence of aryl sulfides and carbon-carbon double bonds. This method is a useful alternative to reduction with triphenyltin hydride (8, 521-522 10, 451-452). 

Selenides are also nucleophilic and produce isolable selenonium salts (9) when treated with alkyl halides. They are easily oxidized to selenoxides (10) and further to selenones (11) under more forcing conditions (see Section 4). Reduction of selenides to the corresponding hydrocarbons is most conveniently achieved with nickel boride,or with tri-n-butyl- or triphenyltin hydride under radical conditions. " Other reagents for reductive deselenization include Raney nickel, lithium triethylborohydride, and lithium in ethylamine (Scheme 4). Benzylic selenides undergo radical extrusion reactions under thermal or photolytic conditions to produce... 

Thiophenes can also be desulfurized to alkenes (RCH2CH=CHCH2R from 39) with a nickel boride catalyst prepared from nickel(II) chloride and NaBH4 in methanol." It is possible to reduce just one SR group of a dithioacetal by treatment with borane-pyridine in trifluoroacetic acid or in CH2CI2 in the presence of AlCl3." ° Phenyl selenides RSePh can be reduced to RH with PhaSnH" and with nickel boride." ° ... 

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