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Updated: Oct 25, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Direct Pyridine Dearomatization via Organocatalytic Enantioselective [4 + 2] Cycloaddition Accessing Polyfused
Shuo Ma1, Xiaotong Li1, Duo Zhou1
1Molecular Synthesis Center & Key Laboratory of Marine Drugs, Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, Qingdao266003, China.
Abstract:
Herein, we report the first chiral phosphoric-acid-catalyzed asymmetric [4 + 2] dearomatization of monocyclic pyridines. Distinct from previous activation modes, this transformation proceeds under purely thermal conditions and does not require external irradiation or photoredox catalysis. Readily accessible nicotinic acid derivatives undergo efficient intramolecular [4 + 2] cycloaddition to furnish polyfused aza-bicyclo[2.2.2]octane frameworks with high levels of enantiocontrol. This work addresses the longstanding challenge associated with the functionalization of monocyclic pyridines and represents the first example of an asymmetric [4 + 2]-cycloaddition-based dearomatization of pyridines.
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Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.

