Browsing by Subject "Frustrated Lewis Pairs"

C-H bonds are abundantly present in organic compounds and therefore represent large class of targets for activation in modern synthetic chemistry. Starting from simple and usually inexpensive compounds, direct activation of C-H bonds provides atom efficient (low waste generation) access to highly functionalized products with high added value. One of the most desirable subclass of C-H bond functionalization is its transformation to C-B bond (borylation), as organoboron compounds are important and widely used building blocks in organic synthesis, in particularly pharmaceuticals, agricultural chemicals and organic materials. Traditionally, transition metal-based catalysts have been used for C-H borylation. Recently, interest has grown towards metal-free approaches. This thesis is focused on the development of metal-free Csp2-H borylation of arenes by coupling two main concepts: borenium cations and Frustrated Lewis Pairs (FLPs). Borenium cations are positively charged boron species possessing two σ-bound substituents, and the third coordination site occupied by a ligand (L) bound through coordinative dative interaction. Due to relative stability ensured by donor ligand and enhanced reactivity owing to unsaturated coordinate sphere and positive charge, chemistry of boreniums attracted considerable attention. FLPs comprise separated (intermolecular) or bound within one molecule (intramolecular) Lewis acidic and Lewis basic components, which are prevented from formation of classical Lewis adduct due to steric repulsion. Since FLPs posses unquenched reactivity they are capable to cleave heterotically σ and π chemical bonds, including C-H bonds. The method showed in the present work implies cooperative actions of 2-aminopyridinyl-borenium based FLPs, comprising borenium cation as LA component, and bulky aminopyridine ligand as LB component to borylate aromatic Csp2-H bonds. In this approach, LA serves as a reagent itself (source of boron), while LB (ligand), which abstract proton upon C-H bond cleavage, can be fully recovered from the reaction mixture. Thus, this approach offers high atom efficiency and low waste generation. We achieved borylation of electron-rich thiophenes, furans, and pyrroles under ambient conditions. Further we dedicated our efforts to improve efficiency and economical aspect of the proposed method.