Preparation of indium nitronates and their Henry reactions
作者:Raquel G. Soengas、Rita Acúrcio、Artur M. S. Silva
DOI:10.1039/c4ob01468e
日期:——
Indium nitronates were readily prepared from commercially available nitroalkanes by transmetallation of the corresponding lithium nitronates with indium salts. The Henryreaction of this indium organometallics with aldehydes afforded β-nitroalkanols in moderate to high yields. The use of chiral sugar aldehydes furnished the corresponding carbohydrate-derived β-nitroalkanols with excellent stereoselectivity
We present herein an improved synthesis of nitro sugars, consisting of a Henry-type reaction of bromonitromethane and sugar aldehydes. The reaction can be promoted by either SmI2 or indium metal, yielding in both cases high yields and good diastereoisomeric ratios. However, while the SmI2-promoted reaction is very sensitive to steric factors and only gives satisfactory results with bromonitromethane, the indium-mediated reaction is not subjected to this limitation, giving excellent results with bromonitromethane as well as more hindered bromonitroalkanes.