Recent Development and Application of Chiral Phase-Transfer Catalysts

Site-specific C-functionalization of free-(NH) peptides and glycine derivatives via direct C–H bond functionalization

“…With 10 mol% CuBr and 1.0 equiv TBHP in 1,2-dichloroethane (DCE), the arylation reaction proceeded efficiently at 100°C, affording the coupling product in 75% isolated yield, using a slight excess of N-PMP glycine amide (1.5 equiv, Table 3, entry 3). Other nonchlorinated solvents, such as THF, 1,6-dioxane, or toluene, afforded low yields of the coupling product (Table 3, entries [4][5][6][7][8]. With this result in hand, we then briefly investigated the scope of this arylation reaction (Table 4).…”

“…Direct and site-specific modification of amino acids and peptides takes advantage of the existing structure and provides a convenient way to generate large arrays of diverse amino acids and peptides for biomedical applications. For amino acid C modifications, known methods include: alkylation of ␣-carbanions (preformed by deprotonation with a strong base) (1)(2)(3)(4), via radicals [␣-bromination by N-bromosuccinimide (5,6) or UV photolysis in the presence of di-tert-butyl peroxide (7)], the Claisen rearrangements (8,9), and the recently reported palladium-catalyzed arylation of an amide (10)(11)(12)(13)(14). In the field of peptide synthesis, stepwise mounting of amino acids via solution and solid phase techniques has been prevalent ever since they were first developed (15,16).…”

“…In another scenario, direct site-specific C-functionalization of peptides provides an ideal approach that takes advantage of the preexisting peptides and provides rapid access to diverse peptide libraries for biological studies. Recently, by using enolate chemistry, O'Donnell (17)(18)(19) and Maruoka (3,4,(20)(21)(22) reported an elegant method to introduce alkyl groups into activated N-terminal glycine unit of a short-chain peptide. However, a general method for site-specifically introducing various functional groups, leading to more elaborated functionalized peptides such as aryl peptides, vinyl peptides, or alkynyl peptides, still does not exist.…”

Acceleration of Acid-Catalyzed Hydrolysis in a Biphasic System by Sodium Tetracyanocyclopentadienides

“…Enantioselective phase-transfer reactions catalyzed by chiral quaternary ammonium salts are one of the representative methods for synthesizing optically active molecules. 2,3) Anionic PTCs have also been developed for reactions where lipophilic anions enhance the solubility of the reactive cationic species, thereby promoting the reactions. Kobayashi et al have reported the first anionic phase-transfer reaction using tetrakis(3,5-bis(trifluoromethyl) phenyl) borate (TFPB) anion.…”

A Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6- Trinitrobenzene under Phase Transfer Catalysis Conditions

“…Phase Transfer Catalysis (PTC), is widely used to promote reaction between two mutually insoluble phases, to give high conversion and selectivity under very mild reaction conditions, and is effective for the reaction we envisaged. Compared with other methods, phase transfer catalysis has long been recognized as a versatile methodology for organic synthesis in both industrial and academic laboratories, is a simple reaction procedure, using safe, inexpensive, environmentally friendly reagents, and affords ease of scale-up and high-pressurereactor-free conditions [19][20][21][22][23].…”