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Ramachandran PV, Lin R, Alawaed AA, Hamann HJ. Aryl carbonyls and carbinols as proelectrophiles for Friedel-Crafts benzylation and alkylation. RSC Adv 2024; 14:15554-15559. [PMID: 38741965 PMCID: PMC11090089 DOI: 10.1039/d4ra02213k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 05/02/2024] [Indexed: 05/16/2024] Open
Abstract
Friedel-Crafts benzylation/alkylation using benzylic, tertiary, and homobenzylic alcohols; aryl aldehydes, aryl ketones, and the highly challenging aryl carboxylic acids and esters as proelectrophiles has been achieved using borane-ammonia and TiCl4, greatly broadening the scope of useable substrates. Incorporation of deactivated aromatic proelectrophiles and specificity for substitution at the benzylic position are demonstrated in the synthesis of various di- and triarylalkane products. Dual protocols allow for the use of standard nucleophilic solvents (benzene, toluene, etc.) or for stoichiometric addition of more valuable nucleophiles including furans, thiophenes, and benzodioxoles.
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Affiliation(s)
- P Veeraraghavan Ramachandran
- Department of Chemistry, Herbert C. Brown Center for Borane Research, Purdue University West Lafayette Indiana 47907 USA
| | - Randy Lin
- Department of Chemistry, Herbert C. Brown Center for Borane Research, Purdue University West Lafayette Indiana 47907 USA
| | - Abdulkhaliq A Alawaed
- Department of Chemistry, Herbert C. Brown Center for Borane Research, Purdue University West Lafayette Indiana 47907 USA
| | - Henry J Hamann
- Department of Chemistry, Herbert C. Brown Center for Borane Research, Purdue University West Lafayette Indiana 47907 USA
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Alawaed AA, Ramachandran PV. TiF 4-catalyzed direct amidation of carboxylic acids and amino acids with amines. Org Biomol Chem 2024; 22:1915-1919. [PMID: 38353662 DOI: 10.1039/d3ob01943h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Unlike other metal fluorides, catalytic titanium tetrafluoride enhances the direct amidation of aromatic and aliphatic carboxylic acids and N-protected amino acids in refluxing toluene. While aromatic acids were converted to amides with 10 mol% of the catalyst within 24 h, aliphatic acids underwent a faster reaction (12 h), with lower catalyst loading (5 mol%). This protocol is equally efficient with alkyl and aryl amines providing a variety of carboxamides and peptides in 60-99% yields.
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Zang Y, Ma Y, Xu Q, Li G, Chen N, Li X, Zhu F. TiCl 4-mediated deoxygenative reduction of aromatic ketones to alkylarenes with ammonia borane. Org Biomol Chem 2024; 22:932-939. [PMID: 38180250 DOI: 10.1039/d3ob01977b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
A rapid and mild protocol for the exhaustive deoxygenation of various aromatic ketones to corresponding alkanes was described, which was mediated by TiCl4 and used ammonia borane (AB) as the reductant. This reduction protocol applies to a wide range of substrates in moderate to excellent yields at room temperature. The gram-scale reaction and syntheses of some key building blocks for SGLT2 inhibitors demonstrated the practicability of this methodology. Preliminary mechanistic studies revealed that the ketone is first converted into an alcohol, which then undergoes a carbocation to give the alkane via hydrogenolysis.
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Affiliation(s)
- Yongjun Zang
- Anhui Province Key Laboratory for Quality Evaluation and Improvement of Traditional Chinese Medicine, Department of Biological and Pharmaceutical Engineering, West Anhui University, Lu'an, 237012, Anhui, P.R. China.
| | - Yunfeng Ma
- Anhui Anlito Biological Technology Co., Ltd, Anhui Huoshan Economic and Technological Development Zone, 237200, Anhui, P.R. China
| | - Qilin Xu
- Anhui Province Key Laboratory for Quality Evaluation and Improvement of Traditional Chinese Medicine, Department of Biological and Pharmaceutical Engineering, West Anhui University, Lu'an, 237012, Anhui, P.R. China.
| | - Guosi Li
- Anhui Province Key Laboratory for Quality Evaluation and Improvement of Traditional Chinese Medicine, Department of Biological and Pharmaceutical Engineering, West Anhui University, Lu'an, 237012, Anhui, P.R. China.
| | - Naidong Chen
- Anhui Province Key Laboratory for Quality Evaluation and Improvement of Traditional Chinese Medicine, Department of Biological and Pharmaceutical Engineering, West Anhui University, Lu'an, 237012, Anhui, P.R. China.
| | - Xing Li
- College of Pharmacy and Chemistry & Chemical Engineering, Taizhou University, Taizhou, 225300, Jiangsu, P.R. China.
| | - Fucheng Zhu
- Anhui Province Key Laboratory for Quality Evaluation and Improvement of Traditional Chinese Medicine, Department of Biological and Pharmaceutical Engineering, West Anhui University, Lu'an, 237012, Anhui, P.R. China.
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