Charge-enhanced thiourea catalysts as hydrogen bond donors for Friedel‒Crafts Alkylations

Smajlagic, Ivor; Carlson, Brenden; Rosano, Nicholas; Foy, Hayden; Dudding, Travis

doi:10.1016/j.tet.2019.130757

Cited by 7 publications

(2 citation statements)

References 64 publications

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“…Our long-standing history in working with cyclopropenium ions − and catalysis ,, prompted this development. Coupled to this was the prospect of synthesizing a structurally unprecedented cationic catalyst, bearing two highly strained aromatic ring systems, namely, a cyclopropenium and a squaramide, together with an electron-deficient aryl group.…”

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Organocatalysis Linked to Charge-Enhanced Acidity with Superelectrophilic Traits

et al. 2022

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Hydrogen bonding is ubiquitous throughout nature and serves as a versatile platform for accessing chemical reactivity. In leveraging this force, chemists have utilized organocatalysts to expand the spectrum of chemical reactivity enabled by hydrogen bonding and at the extreme proton transfer. Despite this broad utility, exploiting charge as a hydrogen-bond activation strategy is unknown for squaramide catalysts. Considering this deficiency, herein, we disclose a cationic squaramide−cyclopropenium organocatalyst displaying charge-enhanced acidity. Key to this advancement was cationic charge, linked to superelectrophilic traits and strong Brønsted acidity, allowing for the construction of unprecedented oxime ether functionality among other important chemical transformations. The origin of this remarkable reactivity was delineated by computational analysis and in-depth experimental mechanistic studies.

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Organocatalysis Linked to Charge-Enhanced Acidity with Superelectrophilic Traits

et al. 2022

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“…For example, significant interest in the catalytic activation of reactants via hydrogen-bonding interactions unquestionably developed the area of hydrogen-bond-donor (HBD) catalysis. [30][31][32] In particular, Friedel-Crafts (FC) alkylation between indole and b-nitro styrene attracted widespread attention due to its acute importance in the production of indole-based biologically active alkaloids. 33 In view of undesired catalyst deactivation via selfquenching of functional groups in homogeneous HBD reactions, integration of active sites into a MOF structure via uniform spatial regulation is the best possible way to evade the unproductive selfassembly.…”

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confidence: 99%