pyrrole-based amino acids have been prepared through the microwave assisted Paal–Knorr reaction of 1–4 ketoesters derived from the corresponding β-ketoester with a functional homologation. The carboxylic group is located in position 3 of the pyrrole, whereas the amino group, protected with the Cbz moiety, is present on the side chain in positions 1 or 2. These compounds were used to prepare constrained oligopeptides
Microwave-Assisted Paal−Knorr Reaction. A Rapid Approach to Substituted Pyrroles and Furans
作者:Giacomo Minetto、Luca F. Raveglia、Maurizio Taddei
DOI:10.1021/ol0362820
日期:2004.2.1
An array of tetrasubstituted pyrroles (and trisubstituted furans) was obtained using a simple three-step procedure. Functional homologation of beta-ketoester with an aldehyde followed by oxidation gave a series of differently substituted 1,4-dicarbonyl compounds that can be rapidly cyclized with the Paal-Knorr procedure carried out under microwave irradiation.
Lewis Acid-Catalyzed Selective [2 + 2]-Cycloaddition and Dearomatizing Cascade Reaction of Aryl Alkynes with Acrylates
selective [2 + 2]-cycloaddition and dearomatizing cascade reaction of aryl alkynes with acrylates with high chemo- and stereoselectivity. The obtained cyclobutene could be easily converted into cyclobutane as well as synthetically useful 1,4- and 1,5-diketones with high chemo- and stereoselectivity. On the basis of mechanistic studies, plausible reaction mechanisms were proposed for both the [2 + 2]-cycloaddition
Microwave-Assisted Paal-Knorr Reaction - Three-Step Regiocontrolled Synthesis of Polysubstituted Furans, Pyrroles and Thiophenes
作者:Giacomo Minetto、Luca F. Raveglia、Alessandro Sega、Maurizio Taddei
DOI:10.1002/ejoc.200500387
日期:2005.12
An efficient and highly versatile synthesis of furans, pyrroles and thiophenes is described. Starting from commercially available or easily prepared β-keto esters, functional homologation provides differently substituted 1,4-diketones that can be transformed, through a microwave-assisted Paal–Knorr condensation, into the corresponding methoxycarbonyl heterocycles. The methoxycarbonyl moiety can be