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Parella R, Jakkampudi S, Bora P, Sakkani N, Zhao JCG. Domino Michael/Michael reaction catalyzed by switchable modularly designed organocatalysts. Org Biomol Chem 2021; 20:163-172. [PMID: 34877959 DOI: 10.1039/d1ob01991k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The domino Michael/Michael reaction between (E)-7-aryl-7-oxohept-5-enals and trans-cinnamaldehydes was investigated by using modularly designed organocatalysts (MDOs). It was found that both the enamine and iminium catalytic modes of the MDOs are switchable and can be individually switched on and off by using appropriate combinations of the precatalyst modules and the reaction conditions. When both the enamine and iminium catalysis modes of the MDOs are switched on, the desired domino reaction products can be obtained in good yields and stereoselectivities under optimized conditions.
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Affiliation(s)
- Ramarao Parella
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-069, USA.
| | - Satish Jakkampudi
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-069, USA.
| | - Pranjal Bora
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-069, USA.
| | - Nagaraju Sakkani
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-069, USA.
| | - John C-G Zhao
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-069, USA.
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Sharma P, Gupta R, Bansal RK. Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides. Beilstein J Org Chem 2021; 17:2585-2610. [PMID: 34760026 PMCID: PMC8551878 DOI: 10.3762/bjoc.17.173] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/27/2021] [Indexed: 11/23/2022] Open
Abstract
Nitrogen-containing scaffolds are ubiquitous in nature and constitute an important class of building blocks in organic synthesis. The asymmetric aza-Michael reaction (aza-MR) alone or in tandem with other organic reaction(s) is an important synthetic tool to form new C-N bond(s) leading to developing new libraries of diverse types of bioactive nitrogen compounds. The synthesis and application of a variety of organocatalysts for accomplishing highly useful organic syntheses without causing environmental pollution in compliance with 'Green Chemistry" has been a landmark development in the recent past. Application of many of these organocatalysts has been extended to asymmetric aza-MR during the last two decades. The present article overviews the literature published during the last 10 years concerning the asymmetric aza-MR of amines and amides catalysed by organocatalysts. Both types of the organocatalysts, i.e., those acting through non-covalent interactions and those working through covalent bond formation have been applied for the asymmetric aza-MR. Thus, the review includes the examples wherein cinchona alkaloids, squaramides, chiral amines, phase-transfer catalysts and chiral bifunctional thioureas have been used, which activate the substrates through hydrogen bond formation. Most of these reactions are accompanied by high yields and enantiomeric excesses. On the other hand, N-heterocyclic carbenes and chiral pyrrolidine derivatives acting through covalent bond formation such as the iminium ions with the substrates have also been included. Wherever possible, a comparison has been made between the efficacies of various organocatalysts in asymmetric aza-MR.
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Affiliation(s)
- Pratibha Sharma
- Department of Chemistry, The IIS (deemed to be University), Jaipur 302 020, India
| | - Raakhi Gupta
- Department of Chemistry, The IIS (deemed to be University), Jaipur 302 020, India
| | - Raj Kumar Bansal
- Department of Chemistry, The IIS (deemed to be University), Jaipur 302 020, India
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Bora P, Jakkampudi S, Parella R, Sakkani N, Dai Q, Bihani M, Arman HD, Zhao JCG. Diastereodivergent synthesis of 4-oxocyclohexanecarbaldehydes by using the modularly designed organocatalysts upon switching on their iminium catalysis. Chem Commun (Camb) 2021; 57:5334-5337. [PMID: 33928958 DOI: 10.1039/d1cc01020d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The cinchona thiourea moiety in the self-assembled modularly designed organocatalysts (MDOs) switches off the iminium catalysis of these catalysts. In this study, it was found that the inhibited iminium catalysis could be switched on by using an appropriate weak acid and that, once the iminium catalysis was switched on, these catalysts could be applied for the highly stereoselective and diastereodivergent synthesis of 4-oxocyclohexanecarbaldehydes via a domino reaction between ketones and α,β-unsaturated aldehydes.
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Affiliation(s)
- Pranjal Bora
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Satish Jakkampudi
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Ramarao Parella
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Nagaraju Sakkani
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Qipu Dai
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Manisha Bihani
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - Hadi D Arman
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
| | - John C-G Zhao
- Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA.
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