Isolation and Crystallographic Characterization of Allylindium Species Generated from Allyl Halide and Indium(0)

Abstract

The reaction of cinnamyl bromide with indium(0) gave two allylindium species, cinnamylindium dibromide and dicinnamylindium bromide. Either species were isolated after complexation of appropriate pyridine-type Lewis bases. The use of 3,5-dibromopyridine (Br 2 py) as a Lewis base gave cinnamylindium dibromide with two Br 2 py ligands. Dicinnamylindium bromide was isolated with 4-(dimethylamino)pyridine (Me 2 Npy) ligands. In both cases, the indium atom showed a trigonal-bipyramidal coordination sphere with the

Characterization of the Nucleophilic Allylindium Species Generated from Allyl Bromide and Indium(0) in Aqueous Media

“…A relatively stable allylindium compound [cinnamylindium prepared from cinnamyl bromide (4) and In 0 ] was investigated in alcohol instead of water as a model reaction of diallylindium decomposition in water. The allylic species generated from cinnamyl bromide with indium(0) in THF, i.e., monoallylindium compound 5 and diallylindium compound 6, [8] were mixed with benzhydrol with stirring at room temperature for 30 min and analyzed by using NMR spectroscopy. [17] As expected, the monoallylindium compound 5 remained unchanged, and the diallylindium compound 6 was converted into the allylindium alkoxide 7 along with the generation of 3-phenylpropene (8) (Scheme 2).…”

“…Recently, we used X-ray crystallographic analysis to determine the structures of the allylindium(III) species generated in organic solvents both by tin/indium transmetalation [7] and by reduction methods. [8] X-ray analysis required stabilization of the indium species by use of appropriate substituents on the allylic carbon chain and ligands to the indium center. [9,10] Many practical synthetic protocols use a reductive method in aqueous media to synthesize allylindium compounds.…”

Recent advances in allylindium reagents in organic synthesis

“…The reaction of the in situ-generated allylindium compounds with benzaldehyde was monitored by NMR spectroscopy, and the results indicated that electronegative substituents retarded the nucleophilicity of the allylindium compounds. 5 This brief review summarizes recent advances in indiummediated, Barbier-type allylations of less-and un-polarized multiple bonds. We hope that the review will provide organic chemists with some insight in this field and serve as a helpful tool in designing synthetic strategies in their research.…”

“…Recently, however, the chemistry of allylindium reagents has been rapidly growing, and widening their applicability in organic synthesis. A more in-depth understanding of the structure and reactivity of allylindium reagents has been established, 5 and various reactions of allylindium reagents have been reported with less-or un-polarized multiple bonds, 6e20 especially with nitrile group-containing substrates. 7b,21e26 Very recently, Baba and co-workers reported the isolation and crystallographic characterization of cinnamylindium species generated from cinnamyl bromide and indium metal for the first time (Scheme 1).…”

“…7b,21e26 Very recently, Baba and co-workers reported the isolation and crystallographic characterization of cinnamylindium species generated from cinnamyl bromide and indium metal for the first time (Scheme 1). 5 The reaction of cinnamyl bromide (1) with indium metal gave two cinnamylindium species, cinnamylindium dibromide 2, and dicinnamylindium bromide 3. The individual species were isolated after complexation of appropriate pyridine-type Lewis bases.…”