Synthesis 2022; 54(04): 887-909
DOI: 10.1055/a-1514-1049
special topic
Cycloadditions – Established and Novel Trends – in Celebration of the 70th Anniversary of the Nobel Prize Awarded to Otto Diels and Kurt Alder

Organocatalyzed Oxa-Diels–Alder Reactions: Recent Progress

Anup Biswas
a   Department of Chemistry, Hooghly Women’s College, Hooghly, West Bengal, India
,
Samrat Kundu
b   Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India   URL: www.msmlabiitkgp.com
,
Dhananjoy Pal
b   Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India   URL: www.msmlabiitkgp.com
,
Amit Pal
b   Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India   URL: www.msmlabiitkgp.com
,
Modhu Sudan Maji
b   Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India   URL: www.msmlabiitkgp.com
› Author Affiliations
M.S.M. gratefully acknowledge the Science & Engineering Research Board (SERB), Department of Science and Technology, New Delhi, India (Sanction No. CRG/2018/000317) for funding. S.K. thanks the University Grants Commission (UGC), India for a fellowship.


Abstract

The oxa-Diels–Alder reaction is a straightforward, atom-economical process for the construction of six-membered oxacycles, which are privileged structures due to their very common occurrence in several pharmaceuticals and natural products. As with many other asymmetric transformations, organocatalysis provides an elegant pathway to their synthesis via [4+2] annulation under mild reaction conditions. The oxa-Diels–Alder reaction utilizes either an α,β-unsaturated carbonyl as an oxa-diene with a suitable dienophile or a simple carbonyl as a dienophile with other dienes. A range of organocatalysts has been explored in the past decade to execute this strategy. The catalysts induce stereoselectivities via two basic reactivities: (1) The formation of chiral intermediates, or (2) selectively activating suitable reactants via a transition state. The present short review compiles organocatalyzed asymmetric oxa-Diels–Alder reactions published over the last ten years, along with detailed discussions on mechanistic approaches.

1 Introduction

2 Catalysis through Covalent Activation

2.1 N-Heterocyclic Carbenes

2.2 Amines

2.3 Isothiourea Catalysis

2.4 Phosphines

3 Catalysis through Non-Covalent Activation

3.1 Bifunctional Amines

3.2 Brønsted Acids

3.3 Guanidines

4 Multicatalysis through Both Covalent and Non-Covalent Activation

5 Conclusion



Publication History

Received: 17 April 2021

Accepted after revision: 20 May 2021

Accepted Manuscript online:
20 May 2021

Article published online:
13 July 2021

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