An Atom-Economical Approach to Conformationally Constrained Tricyclic Nitrogen Heterocycles via Sequential and Tandem Ugi/Intramolecular Diels−Alder Reaction of Pyrrole1,2
Citations Over TimeTop 10% of 2004 papers
Abstract
An efficient approach to rigid tricyclic nitrogen heterocycles via sequential and tandem Ugi/intramolecular Diels-Alder (IMDA) cycloaddition of pyrrole is described. The one-pot Ugi four-component condensation (4CC) reaction was used as the key transformation to prepare trienes with a carboxamide substituent on the tether. The use of acrylic acid (21) and N-propyl- and N-benzylmaleamic acids (24b and 24C) as the acid components provided trienes 22, 25b, and 25c, respectively, which upon heating at 120 degrees C for 12 h yielded the corresponding [4 + 2] cycloaddition products. In the case of maleic acid derivative 24a, heating the reaction mixture at 60 degrees C for 6 h promoted the cycloaddition reaction and provided the desired product 26a in 78% yield. In contrast, fumaric acid monoethyl ester (27a) and 3-acetyl- and 3-(4-methylbenzoyl) acrylic acids (27b-c) directly yielded the corresponding Ugi/IMDA cycloaddition products 29a-c in high yields at room temperature without any trace of initially formed trienes 28a-c. The IMDA cycloaddition reactions proceed with excellent stereoselectivity with the formation of five stereogenic centers and three rings.
Related Papers
- → Resolution/Deracemization of Chiral α-Amino Acids Using Resolving Reagents with Flexible Stereogenic Centers(2009)95 cited
- → Asymmetric Silaboration of Terminal Allenes Bearing α-Stereogenic Centers: Stereoselection Based on “Reagent Control”(2006)53 cited
- → Dibenzylamine substituted cyclotetraphosphazenes: Synthesis, characterization and their stereogenic properties(2018)5 cited
- → Synthesis of atropisomeric diamides with remotely related stereogenic axes by stereoselective additions to imines(1999)24 cited
- → 2.4 General Principles of Diastereoselective Reactions: Acyclic Control of Diastereoselectivity(2012)1 cited