Applications of Pyridines

An excellent example of the application of pyridine lithiation is the synthesis of the fully substituted pyridine atpenin B 255, an antibiotic produced by Penicillium. Its first synthesis, in 1994, was achieved by a series of directed metallations (Scheme 126) which started with 2-chloropyridine 256 and introduced the substituents stepwise around the ring. 2-Chloropyridine can be lithiated ortho-directed by the chlorine) by either LDA or by PhLi, and the organolithium 257 was oxidized to 258 with trimethylborate and then peracetic acid. 0-Methylation and substitution of chloride by methoxide gave 2,3-dimethoxypyridine 259 (Scheme 127). 

The amount of literature on applications of pyridine and benzopyridine derivatives is particularly vast. This necessarily abbreviated presentation is written not as a definitive text, but as an overview in an attempt to convey to the reader the importance and variety of pyridine derivatives in the industrial sphere. 

A final illustration of the diverse applications of pyridines is given by 4-alkyl-2-mercap-topyridines (105), which are used in flotation processes for recovery of metal concentrates from metal-bearing ores (80BRP2046747). 

Some noteworthy reviews on applications of pyridines and their derivatives deal with oligopyridine liquid crystals as novel building blocks for supramolecular architectures based on metal coordination and hydrogen bonding <2000AGE2454>, enantioselective automultiplication of chiral pyridylalkanols by asymmetric autocatalysis <2000ACR382>, and photoactive mono- and polynuclear Cu(i)-phenanthrolines <2001CSR113>. 

One Nitrogen Atom (it is self-subdivided into Pyridines, Pyridinium Compounds, Ylides, Pyridine N-Oxides, Applications of Pyridines, Bipyridines and Related Systems, Hydropyridines, Biologically Active Pyridines and Hydropyridines, Pyridines Annulated with Carbocycles, Pyridines Annulated with Heterocycles). 

The IR spectra (with and without application of pyridine as a probe molecule) of H-ZSM-5 and Co-ZSM-5 prepared via SSIE confirmed the suggestion that in the case of nco/nAi 1.0 the acid Bronsted OH groups were completely consumed. Two types of newly formed acid sites, most likely Lewis acid sites, were indicated, viz., C0CI+ species (vide supra) and possibly true Lewis sites , i.e., Al-containing extra-framework species (cf. [171,172]). 

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