Piperidines alkyl substituted

FDMR has also been used to detect the transient radical cations formed from secondary amines by pulse radiolysis. As mentioned earlier this technique has been used to study a variety of systems such as the radical cation of triethylamine. The radical cations of diethylamine, n-propyl amine and f-butylamine, have also been studied25. The results have shown that the FDMR signal is enhanced with increasing alkyl substitution of the amine as in the pyrrolidines (18) and the piperidines (19)25. 

N-Alkyl-substituted piperidines react autocatalytically at room temperature (in 82-84% yields). However, in the case of acceptor substituents (COMe, C02pt) a basic catalyst is required (triethylamine, yields 64-79%). In addition to EtsN, an electrogenerated base from n-Bu4NBr in CH3CN was applied, enlarging yields by 12-15%. Charge consumption was 0.03-0.05 Faradays/mol, consistent with the catalytic mechanism. The other advantage of the three-component... 

This reaction can furthermore be applied on chiral aminals, affording a straightforward route to optically pure frawi-2,5-pyrrolidines or chiral alkyl-substituted 1,3-oxazoUdines. This method was used for the en an tio selective synthesis of substituted piperidines . 

Oxidative reactions at carbon predominate in the biotransformation of cyclic amiiies, and an important consequence of this is often the cleavage of the carbon-nitrogen bond. For example, A-dealkylation of N- alkyl substituted pyrrolidine (or piperidine, morpholine, etc.) involves an initial oxidative attack at the a- alkyl carbon atom to yield an N hydroxyalkyl derivative (carbinolamine), which is then metabolized to a secondary amine and the corresponding aldehyde. The metabolic conversion of nicotine to nornicotine (30 see Scheme 3) probably involves this mechanism, although the iminium ion (31) has also been suggested as an intermediate in the biotransformation (76JMC1168). Carbinolamines are unstable intermediates and have been identified only in a few cases, e.g. A-hydroxymethylcarbazole... 

As expected, macroscale reduction gave products corresponding to those from reduction of the parent pyridine, that is, piperideines and piperidines. Electrolysis of a series of N-alkyl-substituted 2-pyridones, for example N-methyl-(79), yielded a mixture of A-methylpiperidine and -piperideine 80.126 Reduction of the methyl ether of 2-pyridone gave piperidine only.127... 

C NMR shifts of a number of alkyl substituted piperidines have been documented. (166)... 

Unfortunately, in 3-alkyl-substituted piperidine IV-oxides there is generally little discrimination between the ring a-carbon centers, and mixtures of regioisomeric products are obtained. When a double bond is present in the starting TZ-oxide, however, this functionality will direct the Polonovski reaction towards elimination of one of the allylic hydrogens. Thus, the (Z)-ethylidene product (18) is obtained from (16) after reduction of the conjugated iminium ion intermediate (17 equation S). ... 

A novel and efficient synthesis of 2,5-substituted-l,2,4-triazol-3-ones where various alkyl, aryl, and heterocyclic groups can be introduced successfully at both the N2 and C5 positions has been described <05TL7993>. A practical synthesis of piperidine-/tropane-substituted 1,2,4-triazoles has been reported <05SL1133>. Novel isonucleosides with 1,2,4-triazole-3-earboxamide attaehments were prepared from D-ribose and D-xylose <05SC2653>. 

Following the initial discovery of alkyl-substituted piperidines in Solenopsis venom, a very large number of structurally related alkaloids were identified in the venom from ants of the subfamilies Myrmicinae and Pseudomyrmicinae, all of which share a carbon skeleton based on a single unbranched chain. Analyses of ants from the genera Solenopsis, Monomorium, and Diplorhoptrum revealed 2,5-dialkylated pyrrolidines,... 

While alkyl substituted piperidines have low levels of SRTD activity, the amides, carbamates, and ureas are much more active compounds (Table 2). The 4-fluorophenylurea, Compound 10, has the highest SRTD activity of any compound in the diaminoquinazoline area. The substitution patterns on the aniline and benzo portions of the molecule were reinvestigated with the more active group in Position 4, but the structure-activity relationships were found to be the same as for the 4-cyclohexylamino compounds as described in Figure 1. 

Piperidine alkaloids a group of alkaloids containing the piperidine ring system. Simple P.a. are the alkyl substituted piperidines which occur sporadically. The other P.a. are classified according to their origin, e.g. Coninm alkaloids (see), Punica alkaloids (see), Sedum alkaloids (see) and Lobelia alkaloids (see). These various groups are structurally different and have different mechanisms of biosynthesis. Other P. a. are found in water lilies, and are biosynthesized from mevalonic acid (see Nuphara alkaloids). A de-hydropiperidine structure is present in the Areca alkaloids (see) and the Betalains (see). 

We found that the kinetic resolution of racemic piperidines alkylated at the 2- or 3-p>osition was performed using the provisional enantiomeric conformation of naphthamide 3a derived from chiral crystals. ) Chiral crystals of naphthamide 3a were added to a THF solution of racemic lithium amides prep>ared by the reaction of substituted piperidines with w-BuLi at -80°C the reaction mixture was stirred for 5 hours at -20°C because the substitution reaction did not proceed below -20°C. 

Spin labels are almost invariably di-t-alkyl-substituted nitroxide (nitroxyl or aminoxyl) free radicals. These are used because they are quite stable to heat and light, and nitroxides with a wide variety of structures and functional groups can be readily synthesised, so facilitating the labelling of a range of polymers [4]. Many labels are functionalised piperidine and pyrroline derivatives (Table 9.1), although other types are also sometimes used. 

S.J. Aitken, G. Grogan, C.S.Y. Chow, N.J. Turner, S.L. Flitsch, Biohydroxylations of Cbz-protected alkyl substituted piperidines by Beauveria bassiana ATCC 7159,1. Chem. Soc. Perkin Trans. 1 (1998) 3365-3370. 

The key intermediate, normeperidine (81), is obtained by a scheme closely akin to that used for the parent molecule, Thus, alkylation of phenylacetonitrile with the tosyl analog of the bischloroethyl amine (78) leads to the substituted piperidine... 

The phenothiazine duoperone (5) combines structural elements found in phenothiazine and buty-rophenone antipsychotic agents. Alkylation of substituted piperidine 1 with 3-chloropropanol affords the intermediate 2 treatment of this with thionyl chloride converts the terminal hydroxyl to chloride. Alkylation of the phenothiazine 4 with halide 3 affords the antipsychotic agent duoperone (5) [1]. 

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