2116-65-6Relevant articles and documents
1-acyl-4-benzylpyridinium tetrafluoroborates: Stability, structural properties, and utilization for the synthesis of acyl fluorides
Wagner, Ruediger,Wiedel, Bernd,Guenther, Wolfgang,Goerls, Helmar,Anders, Ernst
, p. 2383 - 2390 (1999)
1-Acyl-4-benzylpyridinium salts 4 containing nonnucleophilic anions X- such as CF3SO3-, FSO3-, and BF4- can be generated quantitatively and in situ from 1-acyl-4-alkylidene-1,4-dihydropyridines 1a-f and the corresponding acid, HX. The BF4- salts reveal an interesting and unexpected thermal instability which allows the convenient synthesis of carboxylic acid fluorides 5b-f. This procedure offers advantages over known methods: All operations can be performed in a standard glass apparatus and do not require high pressures. The formation of RCOF 5 is assisted by the pyridine moiety of 4, which splits off and functions as a Lewis base to intercept the BF3 acid. The structural and electronic relationships as well as dominating differences between the very reactive cations of 4 and their almost 'inert' uncharged precursors, the dihydropyridines 1, are discussed both on the fundament of experimental evidence (X-ray structures of 1f and the extremely reactive and very labile 4f) and theoretical investigations (ab initio and DFT MO calculations).
Practical and Regioselective Synthesis of C-4-Alkylated Pyridines
Baran, Phil S.,Choi, Jin,Godineau, Edouard,Laudadio, Gabriele
, p. 11927 - 11933 (2021/08/20)
The direct position-selective C-4 alkylation of pyridines has been a long-standing challenge in heterocyclic chemistry, particularly from pyridine itself. Historically this has been addressed using prefunctionalized materials to avoid overalkylation and mixtures of regioisomers. This study reports the invention of a simple maleate-derived blocking group for pyridines that enables exquisite control for Minisci-type decarboxylative alkylation at C-4 that allows for inexpensive access to these valuable building blocks. The method is employed on a variety of different pyridines and carboxylic acid alkyl donors, is operationally simple and scalable, and is applied to access known structures in a rapid and inexpensive fashion. Finally, this work points to an interesting strategic departure for the use of Minisci chemistry at the earliest possible stage (native pyridine) rather than current dogma that almost exclusively employs Minisci chemistry as a late-stage functionalization technique.
Lewis Basic Salt-Promoted Organosilane Coupling Reactions with Aromatic Electrophiles
Bandar, Jeffrey S.,Reidl, Tyler W.
supporting information, p. 11939 - 11945 (2021/08/20)
Lewis basic salts promote benzyltrimethylsilane coupling with (hetero)aryl nitriles, sulfones, and chlorides as a new route to 1,1-diarylalkanes. This method combines the substrate modularity and selectivity characteristic of cross-coupling with the practicality of a base-promoted protocol. In addition, a Lewis base strategy enables a complementary scope to existing methods, employs stable and easily prepared organosilanes, and achieves selective arylation in the presence of acidic functional groups. The utility of this method is demonstrated by the synthesis of pharmaceutical analogues and its use in multicomponent reactions.
A Supramolecular Palladium Catalyst Displaying Substrate Selectivity by Remote Control
Zardi, Paolo,Roisnel, Thierry,Gramage-Doria, Rafael
, p. 627 - 634 (2019/01/04)
Inspired by enzymes such as cytochrome P-450, the study of the reactivity of metalloporphyrins continues to attract major interest in the field of homogeneous catalysis. However, little is known about benefitting from the substrate-recognition properties of porphyrins containing additional, catalytically relevant active sites. Herein, such an approach is introduced by using supramolecular ligands derived from metalloporphyrins customized with rigid, palladium-coordinating nitrile groups. According to different studies (NMR and UV/Vis spectroscopy, XRD, control experiments), the supramolecular ligands are able to accommodate pyridine derivatives as substrates inside the porphyrin pocket while the reactivity occurs at the peripheral side. By simply tuning a remote metal center, different binding events result in different catalyst reactivity, and this enzyme-like feature leads to high degrees of substrate selectivity in representative palladium-catalyzed Suzuki–Miyaura reactions.
