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Wang et al. Chem Synth 2023;3:9 Chemical Synthesis
DOI: 10.20517/cs.2022.44

Research Article Open Access

Organocatalytic regio- and enantioselective formal

[4 + 2]-annulation of chiral nitrogen-containing
dipoles

Tao Wang, Boming Shen, Xuling Chen, Qianran Wan, Peiyuan Yu, Pengfei Li *

Shenzhen Grubbs Institute and Department of Chemistry, Guangdong Provincial Key Laboratory of Catalysis, College of Science,
Southern University of Science and Technology (SUSTech), Shenzhen 518055, Guangdong, China.
* Correspondence to: Prof./Dr. Pengfei Li, Shenzhen Grubbs Institute and Department of Chemistry, Guangdong Provincial
Key Laboratory of Catalysis, College of Science, Southern University of Science and Technology (SUSTech), No. 1088
Xueyuan Avenue, Shenzhen 518055, Guangdong, China. E-mail: lipf@sustech.edu.cn; flyli1980@gmail.com

How to cite this article: Wang T, Shen B, Chen X, Wan Q, Yu P, Li P. Organocatalytic regio- and enantioselective formal [4 + 2]-
annulation of chiral nitrogen-containing dipoles. Chem Synth 2023;3:9. https://dx.doi.org/10.20517/cs.2022.44

Received: 30 Dec 2022 First Decision: 19 Jan 2023 Revised: 31 Jan 2023 Accepted: 6 Feb 2023 Published: 15 Feb 2023

Academic Editors: Bao-Lian Su, Da-Gang Yu Copy Editor: Ke-Cui Yang Production Editor: Ke-Cui Yang

Abstract
Quinidine-catalyzed regio- and enantioselective formal [4 + 2]-cycloadditions of 2-(4H-benzo[d][1,3]oxazin-4-
yl)acrylates with N-tosyl-2-methylenebut-3-enoates and 2-methylene-3-oxoalkanoates have been developed for
the first time. The reaction features the in situ formation of chiral nitrogen-containing dipolar intermediates, a ring-
opening/Michael addition/annulation cascade reaction, and works well over a broad substrate scope to furnish the
tetrahydroquinolines in high yields with high asymmetric induction under mild conditions.
Keywords: Annulation, benzoxazine, diene, organocatalysis, tetrahydroquinoline

INTRODUCTION
The enantioenriched tetrahydroquinoline subunit is widely present in compounds with a wide range of
biological activities [Scheme 1A] . Moreover, chiral 1,2,3,4-tetrahydroquinoline phosphoramidites have
[1]
[2]
also been proven to be promising ligands in Ir-catalyzed asymmetric reactions . Accordingly, the
development of new methodologies for the catalyzed asymmetric synthesis of these significant frameworks
[3-7]
continues to be a very active field of research . Particularly, metal-catalyzed decarboxylative
transformations of vinyl benzoxazinones have been identified as a powerful and versatile tool for the

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