Metal‐free catalytic activation and borylation of the ––H bond of 1‐methyl pyrrole using adamantane‐derived aminoborane frustrated Lewis pairs: A density functional theory study

Abstract

Frustrated Lewis pair (FLP) chemistry has developed as a novel strategy for catalysis in organic chemistry and opened a new metal-free organic catalysis area for synthesizing various compounds of interest. Adamantane as molecular scaffolds used to design new sets of FLPs (ambiphilic molecules) for the -C sp 2 -

Transition‐Metal‐Free Heterocyclic Carbon‐Boron Bond Formation

“…Recently, the Ganguly group introduced an adamantyl-based FLP 1-Pip-2-BH 2 -4-F-C 10 H 13 (Cat.-6), which contains a fluorine group at the C4 position of the adamantyl group. [71] DFT analysis showed that this FLP is catalytically most active compared to other FLPs (Cat.-3, Cat.-4, or Cat.-5) for the borylation of 1-methyl pyrrole. The negative inductive effect of the fluorine group increases the acidity of the boron center; hence it will interact strongly with the C2-nucleophilic carbon center of 1-methyl pyrrole and facilitate the CÀ H activation step.…”

Metal‐Free Catalytic Functionalization of Second −Csp2−H Bond of 1‐Methyl Pyrrole Using Bishomocubane‐Derived Aminoborane Frustrated Lewis Pairs: A Computational Study

“…[24] Recently, adamantane-aminoboranes (ADA-aminoborane) as FLP catalysts have been exploited for the À C sp 2À H bond functionalization process. [25] The computational study showed that the newly designed aminoboranes frustrated Lewis pairs with adamantane scaffolds can be a superior catalyst for the CÀ H functionalization of 1-Me-pyrrole. However, the potential energy surface calculated for the second CÀ H functionalization was not energetically feasible with the phenylene aminoboranes.…”

“…The −$${{C}_{{sp}^{2}}}$$ −H bond functionalization of 1‐methyl pyrrole has been reported via phenylene‐aminoborane (Ph‐aminoborane) FLP catalysts [24] . Recently, adamantane‐aminoboranes (ADA‐aminoborane) as FLP catalysts have been exploited for the −$${{{\bf C}}_{{{\bf s p}}^{2}}}$$ −H bond functionalization process [25] . The computational study showed that the newly designed aminoboranes frustrated Lewis pairs with adamantane scaffolds can be a superior catalyst for the C−H functionalization of 1‐Me‐pyrrole.…”

“…The FLP-catalyzed molecular activation processes mainly depend on the steric congestion and electrostatic property of frustrated Lewis pair catalysts. [24,25] The catalyst designing processes are crucial in such reactions; therefore, we have designed new molecular scaffolds for FLP that contain 1,4bishomocubane molecular scaffold and amine-borane Lewis pairs. The newly designed 1,4-BHC aminoboranes examined in this study are shown in Scheme 2 (A&B).…”