2- Pyrrolidinopyridine, reaction with

An important class of IPTC reactions involves the conversion of a reactant and the IPTC catalyst in the organic phase to an ionic intermediate that is transported into the aqueous phase for reaction with the second reactant to yield the organic product and to regenerate the catalyst. This class of IPTC catalysts includes 4-(dimethylamino)pyridine (DMAP), 4-pyrrolidinopyridine, pyridine-1-oxide (PNO), tetrahydrothiophene, and diethylsulfide, etc. Mathias and Vaidya studied the first acylation reaction of alanine with decanoyl- or p-chlorobenzoyl chloride in H2O/CH2CI2 medium catalyzed by DMAP [124]. In this system, the acid chloride reacted with DMAP in the organic phase to form the ionic intermediate,... 

In order to determine the efficiency of the polymers as reagents in nucleophilic catalysis, it was decided to study the rate of quaternization with benzyl chloride. Table I shows the second-order-rate constants for the benzylation reaction in ethanol. Comparison with DMAP indicates that poly(butadiene-co-pyrrolidinopyridine) is the most reactive of all the polymers examined and is even more reactive than the monomeric model. This enhanced reactivity is probably due to the enhanced hydrophobicity of the polymer chain in the vicinity of the reactive sites. 

However, the reaction always led to some overreduction of the pyridine ring. Reduction with BH /THF was unsuccessful. However, NaBH /BF2 Et20 proved to be an excellent reagent for the reduction step, resulting in the formation of the desired polymer. The polymer was shown by UV and NMR spectroscopy to be 67% functionalized primarily with 4-pyrrolidinopyridine moieties by UV and NMR spectroscopy according to these data no starting polymer is present anymore, and the nature of the remaining 23% of functionalization is unknown. 

The reaction of secondary sulfonamides with carboxylic acids in the presence of DCC and4-pyrrolidinopyridine affords N-tosylamides. Also intramolecular cyclization to lactames is achieved using DCC. 

Finally, the application of high-pressure methods (85S1) to the amination of chloro- and bromoquinolines and chloro- or bromopyridines (88H3I9) has been described. Thus, 2-chloropyridine (86) reacts at 60°C and 8 kbar pressure with piperidine to form 2-piperidinopyridine (111) in 12% yield. Analogously, 3-chloropyridine (112) reacts at I00°C with pyrrolidine to give a 10% yield of 3-pyrrolidinopyridine (113), which is, however, obtained in 71% yield under the same reaction conditions from 3-bromo-pyridine (99) (88H3I9). 

Transesterification. Zwitterionic adduct of 4-pyrrolidinopyridine and an electron-deficient aryl isothiocyanate (e.g., p-nitrophenyl and 3,5-bis(trifluoromethyl)phenyl isothiocyanates) catalyzes transesterification of methyl esters, requiring only stoichiometric quantity of the alcohol. The reaction is best performed by azeotropic refluxing, with assistance of 5A-molecular sieves to absorb the liberated MeOH. 

Another strategy for in situ activation, used for the s3uithesis of aliphatic cellulose esters, is the exploitation of DCC in combination with 4-pyrrolidinopyridine (PP) [35]. Among the advantages of this method are the high reactivity of the intermediately formed mixed anhydride with PP and a completely homogeneous reaction in DMA/LiCl up to hexanoic acid. If the reaction is carried out with the anhydrides of carboxylic acids, the carboxylic acid liberated is recycled by forming the mixed anhydride with PP, which is applied only in a catalytic amount. The toxic DCC can be recycled from the reaction mixture (Fig. 16.4). In addition, the method is utilized to obtain unsaturated esters (e.g. methacrylic-, cinnamic-, and vinyl acetic acid esters) and esters of aromatic... 

Aldol-Type Reactions. The facile condensation of 2-trialkyl-silyloxyfurans with carbonyl compounds and their derivatives has spawned many synthetic applications. Aldol products derived from aldehydes, ketones, or acetals can be readily transformed into 4-ylidenebutenolides. Dehydration of 5-(l -hydro-xyalkyl)-2(5//)-furanones is achieved by using acetic anhydride and 4-pyrrolidinopyridine (PPY) in triethylamine (eq 7). ... 

Obtained by reaction of 4-chloro-2-hydroxyacetophenone with 2,4-dichlorobenzoic acid in the presence of N,N-dicyclohexylcarbodiimide and 4-pyrrolidinopyridine in methylene chloride under nitrogen at r.t. for 24 h (81%) [3766]. 

The grafting of nucleic acid base derivatives with a hydroxyl group onto poly(ethyleneimine) polymer backbone was also carried out by the activated ester method. Since the reactivity of the lactone is low, the direct reaction of the lactone derivative with poly(ethyleneimine) was not effective. Therefore, the lactone derivatives were at first hydrolyzed to the 3-hydroxybutyric acid derivatives, followed by condensation with poly(ethyleneimine) using the activated ester method. The grafting reaction was carried out in N,N-dimethylformamide, where a small amount of 4-pyrrolidinopyridine was added as an effective catalyst. Nucleic acid base contents of the polymers were determined by UV spectroscope of hydrolyzed samples. A quantitative calculations were made by using the corresponding carboxyethyl derivatives as standards. The nucleic acid base units (unit mol%) on the polymer are tabulated in Table 1. 

Ester and Thioester Formation. These reactions occur through the same O-acylurea or anhydride active intermediate as in the amide coupling reactions, and the discussion of associated problems applies here as well. In general, alkyl and (particularly) aryl thiols can be efficiently coupled to carboxylic acids using DCC. Reactions of primary and secondary alcohols proceed reliably, but require the presence of an acylation catalyst. This is usually 4-Dimethylaminopyridine (DMAP), " (see also 1,3-Dicyclohexylcarbodiimide—4-Dimethylaminopyridine), but others have been used including 4-pyrrolidinopyridine and pyridine (.solvent) with catalytic p-Toluenesulfonic Acid The acylation of more hindered alcohols often re.sults in reduced yields however, even f-butanol can be acylated, providing a useful route to t-butyl esters. Various other carbodiimide derivatives have also been used in the preparation of esters. As with amides, which are not limited to intermolecular reactions, a wide variety of lactones can also be synthesized. ... 

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