![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
Regioselective Stepwise Synthesis of Unsymmetrical 1,2,5-Triarylpyrroles via Palladium-Catalyzed Decarboxylative
Cindy Buonomano1,2, Stephanie Patterson1, Judith Sorel Ngou1
1Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke O., Montréal, QC H4B 1R6, Canada.
Abstract:
Pyrrole derivatives are natural organic molecules that are important to the pharmaceutical industry due to their occurrence in nature and their use in a wide range of medical applications. In general, non-symmetric, 1,2,5-triaryl-substituted pyrroles are prepared either by Paal-Knorr condensation or cycloaddition that present synthetic challenges particularly if late-stage functionalization is required. The present study describes a modular approach to synthesizing 1,2,5-triarylpyrroles containing three different arene substituents. Using pyrrole ester building blocks, a sequence of decarboxylative cross-coupling and C-H arylation provides unsymmetrical 1,2,5-triarylpyrroles in a regioselective, stepwise manner; the scope and limitations of the sequence are disclosed.
Related Concept Videos
01:16Cycloaddition Reactions: Overview
01:34Woodward–Hoffmann Selection Rules and Microscopic Reversibility
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
01:17Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
02:27Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.