coupling reaction of aromatic and aliphatic ketones including acyclic aliphatic ketones proceeded smoothly to give the corresponding pinacols in good to high yields below room temperature by the combined use of titanium(II) chloride and zinc in the presence of pivalonitrile. Meso-selective formation of the coupling products was observed in the cases with some acyclic aliphatic ketones.
Efficient method for the preparation of pinacols derived from aromatic and aliphatic ketones by using low-valent titanium reagents in dichloromethane-pivalonitrile
aldehydes and ketones, including unsymmetrical aliphatic ketones, proceeded smoothly to give the corresponding pinacols in good to high yields under mild conditions by using combination of titanium(II) chloride and zinc or titanium(IV) chloride and zinc in dichloromethane-pivalonitrile. Meso-selective formation of the coupling products was observed in the cases of some aliphatic ketones. The diastereoselectivities
The structures of diiodosamarium(II) complexes with amide compounds have been investigated basing on single crystalX-ray structural analyses. The reaction of [SmI2(thf)2] with 2 equivalents of tetramethylurea (TMU) gave [SmI2(thf)2(tmu)2] (1). The three different kinds of ligands in 1 attach to the samarium atom in a trans orientation. [SmI2(thf)2] reacted with 4 equivalents of 1,3-dimethyl-2-imidazolidione
Trimethylsilyl chloride-accelerated reduction and pinacol coupling of carbonyl compounds by means of samarium diiodide
作者:Toshio Honda、Miho Katoh
DOI:10.1039/a607774i
日期:——
The combination of samarium diiodide (SmI
2
) and
trimethylsilyl chloride (Me
3
SiCl) in THF–HMPA is found to
accelerate the reduction of sterically hindered and enolisable ketones,
and also to accelerate pinacolisation of the carbonyl compounds depending
on the reaction conditions.
A new convenient preparation of samarium dibromide in THF is reported. Pinacolcoupling reactions using SmBr2 in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonylcompounds.