Electrochemical synthesis pyridines

The industrial and pilot plant applications of electrochemistry of pyridine derivatives will be included in a later chapter6 in this series that chapter will give a description of electrochemical cells employed in large-scale electrochemical synthesis and the problems in scaling up laboratory processes these problems are also treated in some books.7,8... 

W. Flitsch and G. Jones provide the first comprehensive review of pyrrolizine chemistry, an area of increasing interest. The chemistry of the arene oxides has been brought up-to-date by G. S. Shirwaiker and M. V. Bhatt. Following the overall treatment of the electrochemistry of heterocycles given by Lund in Volume 36 of this series, J. E. Toomey has now reviewed electrochemical synthesis and modification of pyridines, a subject of great industrial and academic interest. 

The coordination unit MN6 exists in adducts of the complexes of tosylated 2-aminopyridine with pyridine, 2,2 -bipy, and 1,10-phen (L), obtained as a result of one-step electrochemical synthesis (3.249) [577] ... 

Pyridine is not polarographically reducible in aqueous media in MeCN catalytic hydrogen evolution is the main reaction of protonated pyridine at the cathode [224]. Pyridine can, however, be reduced to piperidine at a lead cathode in 10% H2SO4 [225] the yield is very dependent on the purity of the lead and other components. Side products are a,a, a,y-, and y,)/-dipiperidyl. Pyridine may be reduced to a dimer in liquid ammonia [226]. In MeCN pyridine is reduced in a two-electron wave dihydropyridine and cyanomethylated tetra-hydropyridine are formed, the latter by attack of (CH2CN) on the dihydropyridine [227]. Electrochemical synthesis involving pyridine and its derivatives has been reviewed [Ic]. 

Electrochemical synthesis of pyridines 84AHC(37)167. )8-Hydroxypyridines 82KFZ(4)28. 

A different route to pyrones is the preparative electrochemical oxidation of enamines in acetonitrile in the presence of tetraethylammonium perchlorate (88MI2) (Scheme 46). The synthesis of 2-pyrone derivatives has been carried out by reaction of /3-dicarbonyl compounds with methyl-a-benzoylamino-/3-dimethylaminoacrylate (96JHC751). Thiapyran derivatives can be obtained by interaction of enamines based on (/3-amino-a-cyanoacryloylmethyl)pyridinium chloride derivatives with carbon disulfide (95M711).The synthesis of pyridine derivatives based on analogous enamines has been described as well (95M711). 

Whereas the first synthesis of chemicals by electrolysis dates back over 180 years, the equipment and techniques to understand the fundamentals of these reactions were not developed until recently. This review of electrochemical citations of pyridine compounds of industrial interest is keyed to the functionality of the starting pyridine hence the electrochemistry of pyridines is indexed and not their preparation by electrolysis. 

Electrochemical reduction of the pyridinium compounds (22, R = H, Bu1), prepared by reaction of 6-bromohexan-2-one and the respective pyridine, yields mixtures of the the fused azepines (23) and (24), albeit in low yield <95aG(K)2007>. A new synthesis of claviciptic acid has been published <95Joci486>. 

Electrochemical preparation of an arylzinc bromide and its coupling with 2-chloropyridine synthesis of 2-(4-methoxyphenyl)pyridine... 

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