Piperidinium salt

A nitrogen atom at X results in a variable downfield shift of the a carbons, depending in its extent on what else is attached to the nitrogen. In piperidine (45 X = NH) the a carbon signal is shifted by about 20 p.p.m., to ca. S 47.7, while in A-methylpiperidine (45 X = Me) it appears at S 56.7. Quaternization at nitrogen produces further effects similar to replacement of NH by A-alkyl, but simple protonation has only a small effect. A-Acylpiperidines show two distinct a carbon atoms, because of restricted rotation about the amide bond. The chemical shift separation is about 6 p.p.m., and the mean shift is close to that of the unsubstituted amine (45 X=NH). The nitroso compound (45 X = N—NO) is similar, but the shift separation of the two a carbons is somewhat greater (ca. 12 p.p.m.). The (3 and y carbon atoms of piperidines. A- acylpiperidines and piperidinium salts are all upfield of the cyclohexane resonance, by 0-7 p.p.m. 

Piperidinium chloride, I,I-dimethyI-as plant growth regulator, 1, 191 Piperidinium salts antistatic agents, 1, 409 hair conditioning, 1, 408 NMR, 2, 160 Piperidinols polymers, 1, 284... 

Thioacylsulfanylarsines (RCS2)AsPh2 were synthesized by treating piperidinium dithiocarboxylates with Ph2AsCl.189 The reaction of a -diphenylarsanyl selenoester with piperidine gave diphenylselenoarsinous and diphenyldiselenoarsinic acid piperidinium salts (Scheme 14).190... 

Diphenyldiselenoarsinic acid piperidinium salt was synthesized by the reaction of an dipheny 1 arsany 1 seleno-... 

The formation of lactam 79b from amide 79a as recently published (09OBC3561) is placed first here it proceeds in two steps via acetal hydrolysis and electrophilic cyclization of the intermediate piperidinium salt. 

Very recently the synthesis of the hitherto unknown aromatic xanthate ligands was reported by Fackler et al., who also determined several crystal structures of arylxanthate complexes (117, 238). The synthesis and reactions of air-stable piperidinium salts of aliphatic dithioacids have been reported (377). 

These reactions are best carried out in toluene and/or EtOAc using piperidine/Ac20, or piperidinium salts as well as other amine salts. Hydrochloride salts tend to be even more reactive. L-Proline does not work well for this reaction contrary to other literature accounts, especially in EtOAc. 

Benzaldehyde itself could be the electrophile in this Knoevenagel reaction. However, it is also possible that the piperidinium salt derived from benzaldehyde acts as the electrophile. Similarly, several plausible mechanisms can be formulated for the decarboxylation step—they depend, among other things, on the stage at which it may occur. Because of these ambiguities, we do not want to discuss any of the details of these reaction steps. Instead, we want to focus on a mechanistic detail of the first step and that is the question of which species acts as the nucleophile and initiates the C—C bond formation. 

Tellurium tetrachloride and the potassium or piperidinium salts of thiolobenzoic acid reacted to form tellurium bis[thiolobenzoates]3. 

Tellurium tetrachloride and tellurium tetrabromide reacted with four molar equivalents of dithiocarboxylic acids or their piperidinium salts. Tellurium bis[dithiocarboxylates] were formed1. However, the reaction between tellurapentathionate and dithiocarboxylates is the preferred method for the preparation of tellurium bis[dithiocarboxylates] ... 

Apart from the omnipresent imidazolium based ionic liquids, other classes of low melting salts have been successfully applied in carbon-carbon coupling reactions, notably tetraalkyl ammonium and phosphonium salts. The former include pyrrolidinium and piperidinium salts, but particularly tetrabutylammonium bromide, [(C4)4N]Br (mp. 103-105°C), which has been evaluated quite extensively in Heck reactions and a remarkable increase in reactions rates is frequently observed with this solvent. Those examples where [(C4)4N]Br acts merely as co-catalyst[2"61 rather than as reaction medium shall not be discussed here. 

We were led to the conclusion that in solution as well, at least at low temperature, there is significant interaction between the cation and the chelate anion, perhaps by way of some sort of ion pairing. Although it showed only about 10% more dissociation and no appreciable difference in its usual spectroscopic properties from the piperidinium salt, the tetrapropylammonium salt of the benzoylacetone chelate did not undergo laser action. A cation effect is shown by the data listed in Table II where the tetrapropylammonium ion shows an adverse effect on the laser behavior of BTFA chelates as well. 

At 243°K. in acetonitrile presumably the figure compared with the piperidinium salt at the same temperature will be higher. 

Tellurium tetrachloride and tellurium tetrabromide were converted to tellurium dithiocarboxylate halides in reactions with two or fewer molar equivalents of dithiocarboxylic acids or their piperidinium salts Reactions with a 3 1 molar ratio of the reagents (dithiocarboxylate/tellurium tetrahalide) were not carried out. 

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