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Updated: Jul 12, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
10:17

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones

Published on: February 7, 2019

Base-Catalyzed 1,6-Conjugate Addition/ipso-Cyclization of Ynone-Tethered Pyrroles with para-Quinone Methides: Access

Sofia O Karnakova1, Denis N Tomilin1, Igor A Ushakov1

  • 1A. E. Favorsky Irkutsk Institute of Chemistry SB RAS, 1 Favorsky St, Irkutsk 664033, Russian Federation.

The Journal of Organic Chemistry
|July 10, 2026
PubMed

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Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
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The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
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Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
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