Piperidines, cyanation

Urea maybe reacted with acetoacetic ester and that product nitrated to give 5-nitro-orotec acid That is hydrogenated, then reacted with urea and potassium cyanate to give tetrahydroxypy-imidopyrimidine. The tetrahydroxy compound Is converted to the tetrachloro compound POCI3. Reaction with diethanolamine and then with piperidine gives dipyridamole. 

Scheme 110 Regioselective a-cyanation of piperidine by replacement of a trimethylsilyl group...

A silyl group a to the nitrogen atom in tetrahydroisoquinolines and piperidines governs the regiochemistry, leads to an exclusive cyanation at this position, and additionally lowers the oxidation potential compared to the nonsilylated analogs [47]. Anodic cyanation of A-2,2,2-trifluoroethyl... 

Diethyl amine Fmoc-Ser-OH Boc-Leu-OH Fmoc-Trp-OH Flydrazine Piperidine Triflouroacetic acid Potassium cyanate... 

The i cyanate formed reacts with dry piperidine without cleaving the Si—Si bond ... 

In contrast to that, nucleophilic substitution in a-position to nitrogen by cyanide or methoxide predominates, if the electrolysis is carried out in acetonitrile or methanol in presence of cyanide [49], respectively, in basic methanol [50,51]. This reaction, which is supposed to occur via the iminium ion, is interesting for application in organic synthesis. The formation of synthetically valuable o -aminonitriles from 7V,7V-dialkylani-lines has been reported by Andreades and Zahnow [49]. More recently, a series of papers was published by Hurvois, Moinet, Tallec, et al. on the anodic a-cyanation of A-sub-stituted 1-benzazepines, tetrahydroquinolines, and piperidines [Eq. (9)] [52]. The reactions were performed in a special flow-through cell. In the case of the 3-methyl-substituted benzazepines the reaction is stereospecific, leading only to the trans-a-cyano diastereomer. 

TV-Substituted pyrrolidines (and piperidines) are, similarly to other tertiary aliphatic amines, anodically cyanated a to the nitrogen in aqueous methanolic solution containing sodium cyanide [216]. 

Cycloaddition of 2-(dicyanomethylene)piperidine with iso(thio) cyanates afforded 3-imino-4-cyano-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidin-l-ones or -1-thiones (198, = H, X = O or S) (78MI1). When... 

Electrochemistry has been used for both a- and p-fimctionalization of piperidines for example, oxo groups have been introduced into P-position of N-methoxycarbonylpiperidine using electrochemical oxidation <94BCSJ(67)304). a-Cyanation of A -benzylpiperidine was achieved using electrochemical oxidative cyanation approach (94H(38)1711). 

The one-pot diphenylproHnol silyl ether 1 catalyzed Michael reaction of cro-tonaldehyde and nitroalkene arrives at the intermediate 247, which is followed by the an aza-Henry reaction/hemiaminalization process to a proposed alcohol intermediate, followed by Lewis acid-mediated allylation or cyanation (Scheme 7.54). A later report of polysubstituted piperidine 251 preparation was carried out through a Michael addition of 249 and 250 and an aminahzation reaction process, remarkably in water [123]. This process was also carried out to form tetrahydropyrans... 

Z)-Alk-2-enenitriles are also available from the hydrocyanation of acetylenes, which occurs with cis stereospecificity when catalysed by a nickel(O) complex, and from the stereoselective cyanation of vinyl halides, catalysed by tetracyano-cobaltate(i). The latter procedure is equally applicable to the stereoselective synthesis of the corresponding ( )-isomers. Also, the ( )- and (Z)-isomers (17) and (18) react with piperidine with retention of configuration to provide (19) and (20) respectively (Scheme 30). In contrast, the corresponding reaction with sodium methoxide gives rise to the (Z)-isomer only. 

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