Site‐Selective Nitrene Transfer to Conjugated Olefins Directed by Oxazoline Peptide Ligands

Storch, Golo; Heuvel, Naudin van den; Miller, Scott J.

doi:10.1002/adsc.201900631

Cited by 4 publications

(3 citation statements)

References 60 publications

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“…In that process, the caveat of requiring a specific functional group is compensated by the fact that terminal alcohols are ubiquitous, and the resulting reaction is highly effective and general. Substrate-directed strategies have barely been explored for enantioselective aziridination, although they have been used to exert control over diastereoselectivity as well as site-selectivity (Figure c, upper). , To the best of our knowledge, the only substrate-directed aziridination to control enantioselectivity is that developed by Zhong and Bach in which a chiral lactam motif is appended to a Rh 2 (esp) 2 -derived complex (Figure c, lower) . In this system, dual hydrogen bonding interactions with a quinoline-containing substrate present the alkene to the Rh-nitrenoid in a chiral environment.…”

Section: Introductionmentioning

confidence: 99%

Substrate-Directed Enantioselective Aziridination of Alkenyl Alcohols Controlled by a Chiral Cation

et al. 2023

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Alkene aziridination is a highly versatile transformation for the construction of chiral nitrogen-containing compounds. Inspired by the success of analogous substrate-directed epoxidations, we report an enantioselective aziridination of alkenyl alcohols, which enables asymmetric nitrene transfer to alkenes with varied substitution patterns, including those not covered by the current protocols. We believe that our method is effective because it is substrate-directed, exploiting a network of attractive non-covalent interactions between the substrate, an achiral dianionic rhodium(II,II) tetracarboxylate dimer, and its two associated cinchona alkaloid-derived cations. It is these cations that provide a defined chiral pocket in which the aziridination can occur. In addition to a thorough evaluation of compatible alkene classes, we advance a practical mnemonic to predict reaction outcome and disclose a range of post-functionalization protocols that highlight the unique synthetic potential of the enantioenriched aziridine-alcohol products.

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Section: Introductionmentioning

confidence: 99%

Substrate-Directed Enantioselective Aziridination of Alkenyl Alcohols Controlled by a Chiral Cation

et al. 2023

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“…To date, the selective amination of aliphatic C(sp 3 )–H bonds has mainly been limited to the site-selectivity of unactivated substrates (e.g., tertiary alkyl C–H bonds and benzylic γ-C–H bonds) and activated substrates (e.g., allylic and benzylic C–H bonds)23, [ 25 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Due to the similar high bond-dissociation energy of aliphatic C-H bonds, only a handful of studies have been conducted to identify the selective amination of aliphatic C(sp 3 )–H bonds.…”

Section: Introductionmentioning

confidence: 99%

Silver Catalyzed Site-Selective C(sp3)−H Bond Amination of Secondary over Primary C(sp3)−H Bonds

et al. 2022

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Sulfamates are widespread in numerous pharmacologically active molecules. In this paper, Silver/Bathophenanthroline catalyzed the intramolecular selective amination of primary C(sp3)−H bonds and secondary C(sp3)−H bonds of sulfamate esters, to produce cyclic sulfamates in good yields and with a high site-selectivity. DFT calculations revealed that the interaction between sulfamates and L10 makes the molecule more firmly attached to the catalyst, benefiting the catalysis reaction. The in vitro anticancer activity of the final products was evaluated in MCF-7 breast cancer cells.

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“…Aziridines are important synthetic intermediates in organic synthesis, medicinal chemistry, and polymer chemistry, Catalytic approaches to their syntheses have rapidly expanded in recent years , . Transition metal‐catalyzed reactions involving nitrene transfer to alkenes have gained prominence in this regard , .…”

Section: Introductionmentioning

confidence: 99%

Silver(I) and Copper(I) Complexes of Semi‐Bulky Nitrogen‐Confused C‐Scorpionates

et al. 2020

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Two new sterically demanding nitrogen-confused C-scorpionate ligands with a bis(3,5-diisopropylpyrazol-1yl)methyl group bound to the 3-position of a normal pyrazole ( H L iPr2 ) or an N-toluenesulfonyl pyrazole ( Ts L iPr2 ) have been prepared. Reactions between the ligands ( x L iPr2 ) and silver trifluoromethanesulfonate, AgOTf, gave four new compounds of the types [Ag(Ts, 1b; x = H, 2b) depending on the initial metal:ligand ratio. Similarly, the reactions with [Cu(CH 3 CN) 4 ](PF 6 ) produce [a] Dr.to trap and spectroscopically characterize the nitrene intermediates {[(2-py)Bpm R3R5 ]Cu(NTs)} + in CH 2 Cl 2 at -78°C using (2-tBuSO 2 )C 6 H 4 I=NTs [34] as a soluble nitrene source. The spectroscopic and magnetic data were consistent with diamagnetic, singlet species at -78°C. Calculations showed ground state triplet but all spin states [ 1/3 Cu I -nitrene or 1/3 Cu II -N·(iminyl)] and nitrene binding modes (κ 1 N-, κ 2 N,O-) are thermally accessible. These intermediates were capable of stoichiometrically transferring a nitrene unit to a variety of substrates. Then, different {[(2-py)Bpm R3R5 ]Cu(CH 3 CN)}(PF 6 ) complexes were found to be capable catalysts for nitrene transfer to unsubstituted or p-substituted styrenes giving modest yields (> 65 %) of aziridine under mild ocnditions (PhI=NTs/CH 2 Cl 2 /295 K, 24 h).In a previous study, [27] eight complexes of the type [Ag( x L R ) n ](OTf ) (n = 1, 2 and x L R = H L, Ts L, H L*, and Ts L*) were characterized and evaluated for their ability to catalyze aziridination of styrene. Both ESI(+) MS and NMR spectroscopic studies indicated that the analytically pure [Ag( x L R ) n ](OTf ) compounds did not retain their structure in CH 3 CN rather were involved in multiple dynamic equilibria in solution. These dynamic processes remained in the fast exchange regime on the NMR timescale down to the freezing point of the solvent, thereby obfuscating structural information. These silver complexes of nitrogen-confused C-scorpionates showed no or very little capacity to participate in styrene aziridination using PhI= NTs in room temperature CH 2 Cl 2 . However, [Ag( x L R ) n ](OTf ) showed modest catalytic activity at 80°C in CH 3 CN when employing a nitrene generated in-situ from H 2 NTs and PhI(OAc). Interestingly, the bulkiest derivative [Ag( Ts L * ) 2 ](OTf ) was reported to have the highest activity giving 34 % yield of the desired N-tosyl aziridine. This observation prompted the current study to determine if further increasing steric bulk of the ligands would lead to an increase in catalytic activity of silver complexes. Herein we report on the preparation of two new semi-bulky nitrogen confused scorpionates, Ts L iPr2 and H L iPr2 and their silver(I) and copper(I) complexes. The copper(I) complexes were prepared to compare catalytic activity with their silver congeners, and possibly to demonstrate the generality of any trends in ligand sterics on catalytic activity. It was also hoped that the slower ligand exchange rates associated with the smaller copper(I) compared ...

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Site‐Selective Nitrene Transfer to Conjugated Olefins Directed by Oxazoline Peptide Ligands

Cited by 4 publications

References 60 publications

Substrate-Directed Enantioselective Aziridination of Alkenyl Alcohols Controlled by a Chiral Cation

Substrate-Directed Enantioselective Aziridination of Alkenyl Alcohols Controlled by a Chiral Cation

Silver Catalyzed Site-Selective C(sp3)−H Bond Amination of Secondary over Primary C(sp3)−H Bonds

Silver(I) and Copper(I) Complexes of Semi‐Bulky Nitrogen‐Confused C‐Scorpionates

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