Hydrogenation of alkenes with sodium borohydride and moist alumina catalyzed by nickel chloride

Sodium borohydride-nickel chloride hexahydrate in EtOH/PEG-400 as an efficient and recyclable catalytic system for the reduction of alkenes

“…Importantly, the appropriate amounts of the NaBH 4 were only 0.5 molar equivalents (entry 4), which were lower than those in the earlier reports. 12,15,23,24 This is possibly because the hydrogen source for the reduction can be sufficiently derived from the B-H of NaBH 4 and the O-H of ethanol in our catalytic system (ideally 1 molar of NaBH 4 can reduce 4 molar of alkenes with ethanol), as recently reported by Bai et al for the semihydrogenation of alkynes with NaBH 4 in methanol. 25 The activity of the in situ generated Ni (0) NPs catalyst in EtOH/PEG-400 (3/2 ratio) had also been compared with the commercial RANEY® nickel catalyst.…”

“…28,29 However, prolonging the reaction time from 15 min to 120 min could still keep a high yield of ethylbenzene. Notably, the activities of Ni (0) NPs from second run still higher than the corresponding heterogeneous Ni NPS on moist alumina reported by Takashi Morimoto et al 12 To explore the reason why the catalytic activity decreased aer rst run, the leaching, size and distribution of Ni NPs were characterized aer reaction. The leached Ni species were checked by ICP-AES and found to be only 0.3%.…”

“…18 Immobilized nanoparticles (NPs) on insoluble solid supports were generally used for this process in the past literature. 12,15,16 One signicant example was that Takashi Morimoto and coworkers reached 90% yield of ethylbenzene within 3 h using NiCl 2 $6H 2 O on moist alumina reducted by NaBH 4 in hexane at 30 C. 12 Unfortunately, heterogeneous catalysts of NPS on solid supports are oen more inert than corresponding soluble NPs catalysts. 19 In view of the above, we wanted to explore the use of soluble NPs generated in situ for this process.…”

A Generic Approach for the Catalytic Reduction of Nitriles.

“…28 Isolated double bonds were hydrogenated by this metal boride system (entries 14 and 15), as previously reported in the literature. 4,29 In some cases, however, when cobalt salts were employed no reduction of the double bond occurred. 13 As documented in the literature 4,30 a ketone was found to be reduced to the corresponding secondary alcohol (entry 28) in the presence of a boride species and excess borohydride.…”

NiCl2and NiCl2= 6H2O: A very Useful Mild Lewis Acid in Organic Synthesis

“…2 (H) In the presence of moist alumina, aliphatic and aromatic alkenes were hydrogenated quantitatively to alkanes under mild conditions with NaBH 4 /NiCl 2 . 8 …”