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Kumari R, Jha AK, Khan AGH, Easwar S. Mechanistic Investigations on the Interaction of Morita-Baylis-Hillman Ketones with 2-Aminothiophenol. J Org Chem 2024; 89:7263-7269. [PMID: 38684077 DOI: 10.1021/acs.joc.3c02993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The reaction of Morita-Baylis-Hillman ketones with 2-aminothiophenol mediated by Cs2CO3 results in an oxidative cyclization to 2,2-disubstituted dihydro-1,4-benzothiazines, with the structure of the product indicating the occurrence of an aza-Michael addition along the pathway. In contrast, in the absence of a base, the parent compounds interact to produce a thia-Michael adduct instead. A deeper mechanistic study improved our understanding of the apparent contradiction and provided insight into the base-dependent switch in reactivity.
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Affiliation(s)
- Rajkiran Kumari
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri District, Ajmer, Rajasthan 305817, India
| | - Ajit Kumar Jha
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri District, Ajmer, Rajasthan 305817, India
| | - Akram Gulam Hussain Khan
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri District, Ajmer, Rajasthan 305817, India
| | - Srinivasan Easwar
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri District, Ajmer, Rajasthan 305817, India
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Kumari R, Jha AK, Goyal S, Maan R, Reddy SR, Easwar S. Acyl Transfer-Driven Rauhut-Currier Dimerization of Morita-Baylis-Hillman Ketones. J Org Chem 2023; 88:2023-2033. [PMID: 36753536 DOI: 10.1021/acs.joc.2c02244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
A serendipitous Rauhut-Currier dimerization of 1,1-disubstituted activated olefins derived from Morita-Baylis-Hillman adducts was observed in the presence of DABCO. The reaction is driven by the migration of an acyl group and produces multifunctionalized enol esters in yields greater than 90% in most cases, without necessitating column chromatographic purification. The acyl transfer is thought to proceed via a transition state typical of a Morita-Baylis-Hillman (MBH) reaction, supported by a brief mechanistic study involving computational calculations.
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Affiliation(s)
- Rajkiran Kumari
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
| | - Ajit Kumar Jha
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
| | - Sophiya Goyal
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
| | - Reena Maan
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
| | - S Rajagopala Reddy
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
| | - Srinivasan Easwar
- Department of Chemistry, School of Chemical Sciences and Pharmacy, Central University of Rajasthan, NH-8, Bandarsindri, Ajmer 305817, Rajasthan, India
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Borra S, Chae S, Kim HY, Oh K. Continuous Flow Synthesis of 1,4-Benzothiazines Using Ambivalent Reactivity of ( E)-β-Chlorovinyl Ketones: A Point of Reaction Control Enabled by Flow Chemistry. Org Lett 2022; 24:5287-5292. [PMID: 35848887 DOI: 10.1021/acs.orglett.2c01865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A continuous flow system to 1,4-benzothiazines was developed using the point of reaction control, where the ambivalent (E)-β-chlorovinyl ketones and 2,2'-dithiodianilines were confined in a diffusion controlled flow setting. The successful segregation of reactive chemical species in a flow setting allowed more defined reaction pathways that are not feasible in traditional batch reaction conditions. The point of reaction control in flow systems helps to execute the reactions often plagued with the concurrent generation of multiple chemical species.
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Affiliation(s)
- Satheesh Borra
- Center for Metareceptome Research, Graduate School of Pharmaceutical Sciences, Chung-Ang University, 84 Heukseok-ro, Dongjak, Seoul 06974, Republic of Korea
| | - Soyeon Chae
- Department of Global Innovative Drugs, Chung-Ang University, 84 Heukseok-ro, Dongjak, Seoul 06974, Republic of Korea
| | - Hun Young Kim
- Department of Global Innovative Drugs, Chung-Ang University, 84 Heukseok-ro, Dongjak, Seoul 06974, Republic of Korea
| | - Kyungsoo Oh
- Center for Metareceptome Research, Graduate School of Pharmaceutical Sciences, Chung-Ang University, 84 Heukseok-ro, Dongjak, Seoul 06974, Republic of Korea
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