Halo-1,2,3-triazolium Salts as Halogen Bond Donors for the Activation of Imines in Dihydropyridinone Synthesis

Kaasik, Mikk; Metsala, Andrus; Kaabel, Sandra; Kriis, Kadri; Järving, Ivar; Kanger, Tõnis

doi:10.1021/acs.joc.9b00248

Cited by 55 publications

(43 citation statements)

References 71 publications

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“…Previous publications clearly found that for the activation of neutral compounds, counter anions more weakly coordinating than triflate are necessary . Thus, an exchange to the corresponding BAr F 4 salt was performed via simple metathesis with TMABAr F 4 , affording 9 Im‐CF3‐BArF4 …”

Section: Resultsmentioning

confidence: 99%

Preorganization: A Powerful Tool in Intermolecular Halogen Bonding in Solution

2020

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Preorganization is a powerful tool in supramolecular chemistry which has been utilized successfully in intra‐ and intermolecular halogen bonding. In previous work, we had developed a bidentate bis(iodobenzimidazolium)‐based halogen bond donor which featured a central trifluoromethyl substituent. This compound showed a markedly increased catalytic activity compared to unsubstituted bis(iodoimidazolium)‐based Lewis acids, which could be explained either by electronic effects (the electron withdrawal by the fluorinated substituent) or by preorganization (the hindered rotation of the halogen bonding moieties). Herein, we systematically investigate the origin of this increased Lewis acidity via a comparison of the two types of compounds and their respective derivatives with or without the central trifluoromethyl group. Calorimetric measurements of halide complexations indicated that preorganization is the main reason for the higher halogen bonding strength. The performance of the catalysts in a series of benchmark reactions corroborates this finding.

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Section: Resultsmentioning

confidence: 99%

Preorganization: A Powerful Tool in Intermolecular Halogen Bonding in Solution

2020

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“…Halogen bonding is being actively studied, and it has been demonstrated that it plays a significant role in biochemistry [22,23], in crystal design and design of functional materials (liquid crystals, molecular receptors, conductors, luminescence emitters, non-linear optical materials, etc.) [24][25][26][27][28][29][30][31][32], in organocatalysis [33][34][35][36][37][38] and in design of pharmaceuticals (here, halogen bonds are considered primarily as a type of hydrophobic functional groups, increasing the lipophilic properties of molecules and allowing them to pass through cell membranes) [39,40]. Besides, the halogen bond has been a subject of numerous theoretical works [41][42][43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy

et al. 2020

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An extensive series of 128 halogen-bonded complexes formed by trimethylphosphine oxide and various F-, Cl-, Br-, I- and At-containing molecules, ranging in energy from 0 to 124 kJ/mol, is studied by DFT calculations in vacuum. The results reveal correlations between R–X⋅⋅⋅O=PMe3 halogen bond energy ΔE, X⋅⋅⋅O distance r, halogen’s σ-hole size, QTAIM parameters at halogen bond critical point and changes of spectroscopic parameters of phosphine oxide upon complexation, such as 31P NMR chemical shift, ΔδP, and P=O stretching frequency, Δν. Some of the correlations are halogen-specific, i.e., different for F, Cl, Br, I and At, such as ΔE(r), while others are general, i.e., fulfilled for the whole set of complexes at once, such as ΔE(ΔδP). The proposed correlations could be used to estimate the halogen bond properties in disordered media (liquids, solutions, polymers, glasses) from the corresponding NMR and IR spectra.

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“…In recent years, despite the development of excellent proof-ofconcept XB-catalyzed reactions by multiple research groups [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] , protocols whereby XB catalysis shows clear catalytic advantages in over conventional thiourea catalysis is lacking 21 . Moreover, a conceivable configurational advantage pertaining to XB catalysis would involve the ease of σ-hole tunability via halogen swapping to accommodate challenging substrates-an advantage not well adoptable in thiourea catalysis due to strict requirements of hydrogen atoms for dual HB activation.…”

mentioning

confidence: 99%

A robust and tunable halogen bond organocatalyzed 2-deoxyglycosylation involving quantum tunneling

Xu¹,

Rao²,

Weigen³

et al. 2020

Nat Commun

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The development of noncovalent halogen bonding (XB) catalysis is rapidly gaining traction, as isolated reports documented better performance than the well-established hydrogen bonding thiourea catalysis. However, convincing cases allowing XB activation to be competitive in challenging bond formations are lacking. Herein, we report a robust XB catalyzed 2-deoxyglycosylation, featuring a biomimetic reaction network indicative of dynamic XB activation. Benchmarking studies uncovered an improved substrate tolerance compared to thiourea-catalyzed protocols. Kinetic investigations reveal an autoinductive sigmoidal kinetic profile, supporting an in situ amplification of a XB dependent active catalytic species. Kinetic isotopic effect measurements further support quantum tunneling in the rate determining step. Furthermore, we demonstrate XB catalysis tunability via a halogen swapping strategy, facilitating 2-deoxyribosylations of D-ribals. This protocol showcases the clear emergence of XB catalysis as a versatile activation mode in noncovalent organocatalysis, and as an important addition to the catalytic toolbox of chemical glycosylations.

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Halo-1,2,3-triazolium Salts as Halogen Bond Donors for the Activation of Imines in Dihydropyridinone Synthesis

Cited by 55 publications

References 71 publications

Preorganization: A Powerful Tool in Intermolecular Halogen Bonding in Solution

Preorganization: A Powerful Tool in Intermolecular Halogen Bonding in Solution

Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy

A robust and tunable halogen bond organocatalyzed 2-deoxyglycosylation involving quantum tunneling

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