Tantalum Ureate Complexes for Photocatalytic Hydroaminoalkylation

Overview

Journal Chem Sci

Publisher Royal Society of Chemistry

Specialty Chemistry

Date 2023 May 14

PMID 37181785

Authors

Han Hao

Manfred Manssen

Laurel L Schafer

Affiliations

Soon will be listed here.

Abstract

Using a tantalum ureate pre-catalyst, photocatalytic hydroaminoalkylation of unactivated alkenes with unprotected amines at room temperature is demonstrated. The combination of Ta(CHSiMe)Cl and a ureate ligand with a saturated cyclic backbone resulted in this unique reactivity. Preliminary investigations of the reaction mechanism suggest that both the thermal and photocatalytic hydroaminoalkylation reactions begin with N-H bond activation and subsequent metallaaziridine formation. However, a select tantalum ureate complex, through ligand to metal charge transfer (LMCT), results in photocatalyzed homolytic metal-carbon bond cleavage and subsequent addition to unactivated alkene to afford the desired carbon-carbon bond formation. Origins of ligand effects on promoting homolytic metal-carbon bond cleavage are explored computationally to support enhanced ligand design efforts.

References

Bielefeld J, Doye S . Fast Titanium-Catalyzed Hydroaminomethylation of Alkenes and the Formal Conversion of Methylamine. Angew Chem Int Ed Engl. 2020; 59(15):6138-6143. PMC: 7187458. DOI: 10.1002/anie.202001111. View

Edwards P, Schafer L . Early transition metal-catalyzed C-H alkylation: hydroaminoalkylation for C-C bond formation in the synthesis of selectively substituted amines. Chem Commun (Camb). 2018; 54(89):12543-12560. DOI: 10.1039/c8cc06445h. View

Askey H, Grayson J, Tibbetts J, Turner-Dore J, Holmes J, Kociok-Kohn G . Photocatalytic Hydroaminoalkylation of Styrenes with Unprotected Primary Alkylamines. J Am Chem Soc. 2021; 143(39):15936-15945. PMC: 8499025. DOI: 10.1021/jacs.1c07401. View

Choi G, Zhu Q, Miller D, Gu C, Knowles R . Catalytic alkylation of remote C-H bonds enabled by proton-coupled electron transfer. Nature. 2016; 539(7628):268-271. PMC: 5704892. DOI: 10.1038/nature19811. View

Zi G, Zhang F, Song H . Highly enantioselective hydroaminoalkylation of secondary amines catalyzed by group 5 metal amides with chiral biarylamidate ligands. Chem Commun (Camb). 2010; 46(34):6296-8. DOI: 10.1039/c0cc01265c. View

Ruiz Espelt L, McPherson I, Wiensch E, Yoon T . Enantioselective conjugate additions of α-amino radicals via cooperative photoredox and Lewis acid catalysis. J Am Chem Soc. 2015; 137(7):2452-5. PMC: 4547529. DOI: 10.1021/ja512746q. View

Bexrud J, Eisenberger P, Leitch D, Payne P, Schafer L . Selective C-H activation alpha to primary amines. Bridging metallaaziridines for catalytic, intramolecular alpha-alkylation. J Am Chem Soc. 2009; 131(6):2116-8. DOI: 10.1021/ja808862w. View

Geik D, Rosien M, Bielefeld J, Schmidtmann M, Doye S . Titanium-Catalyzed Intermolecular Hydroaminoalkylation of Alkenes with Tertiary Amines. Angew Chem Int Ed Engl. 2021; 60(18):9936-9940. PMC: 8251730. DOI: 10.1002/anie.202100431. View

Eisenberger P, Ayinla R, Lauzon J, Schafer L . Tantalum-amidate complexes for the hydroaminoalkylation of secondary amines: enhanced substrate scope and enantioselective chiral amine synthesis. Angew Chem Int Ed Engl. 2009; 48(44):8361-5. DOI: 10.1002/anie.200903656. View

10.

Reznichenko A, Hultzsch K . The mechanism of hydroaminoalkylation catalyzed by group 5 metal binaphtholate complexes. J Am Chem Soc. 2012; 134(6):3300-11. DOI: 10.1021/ja211945m. View

11.

Prochnow I, Zark P, Muller T, Doye S . The mechanism of the titanium-catalyzed hydroaminoalkylation of alkenes. Angew Chem Int Ed Engl. 2011; 50(28):6401-5. DOI: 10.1002/anie.201101239. View

12.

Weers M, Luhning L, Luhrs V, Brahms C, Doye S . One-Pot Procedure for the Synthesis of 1,5-Benzodiazepines from N-Allyl-2-bromoanilines. Chemistry. 2016; 23(6):1237-1240. DOI: 10.1002/chem.201604561. View

13.

Trowbridge A, Walton S, Gaunt M . New Strategies for the Transition-Metal Catalyzed Synthesis of Aliphatic Amines. Chem Rev. 2020; 120(5):2613-2692. DOI: 10.1021/acs.chemrev.9b00462. View

14.

Miyake Y, Nakajima K, Nishibayashi Y . Visible-light-mediated utilization of α-aminoalkyl radicals: addition to electron-deficient alkenes using photoredox catalysts. J Am Chem Soc. 2012; 134(7):3338-41. DOI: 10.1021/ja211770y. View

15.

Bielefeld J, Doye S . Dimethylamine as a Substrate in Hydroaminoalkylation Reactions. Angew Chem Int Ed Engl. 2017; 56(47):15155-15158. DOI: 10.1002/anie.201708959. View

16.

Lin S, Sun G, Kang Q . A visible-light-activated rhodium complex in enantioselective conjugate addition of α-amino radicals with Michael acceptors. Chem Commun (Camb). 2017; 53(54):7665-7668. DOI: 10.1039/c7cc03650g. View

17.

Zhang Y, Lee T, Favale J, Leary D, Petersen J, Scholes G . Delayed fluorescence from a zirconium(IV) photosensitizer with ligand-to-metal charge-transfer excited states. Nat Chem. 2020; 12(4):345-352. DOI: 10.1038/s41557-020-0430-7. View

18.

McManus J, Onuska N, Nicewicz D . Generation and Alkylation of α-Carbamyl Radicals via Organic Photoredox Catalysis. J Am Chem Soc. 2018; 140(29):9056-9060. DOI: 10.1021/jacs.8b04890. View

19.

Hioe J, Sakic D, Vrcek V, Zipse H . The stability of nitrogen-centered radicals. Org Biomol Chem. 2014; 13(1):157-69. DOI: 10.1039/c4ob01656d. View

20.

Musacchio A, Lainhart B, Zhang X, Naguib S, Sherwood T, Knowles R . Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines. Science. 2017; 355(6326):727-730. PMC: 5426363. DOI: 10.1126/science.aal3010. View