Pyrrolidinium salt

The enamino ketone (49) was reported to give no identifiable products on reaction with N,N-dimethyl carbamoyl chloride 63). However, reaction of (49) with N,N-diethyl carbamoyl chloride in refluxing chlorobenzene gave the N-(3-diethyl-amino-5,5-dimethylcyclohex-2-en-1 -ylidene)pyrrolidinium salt, isolated as the perchlorate. The latter must have been formed as outlined in Scheme I, involving initial O carbamoylation followed by an addition-elimination reaction to give 138 cation which can react with diethylamino anion by a further addition-elimination displacement to give the product 46). 

A variety of imidazolidinium and pyrrolidinium salts (Fig. 2.38) have been found to catalyze the reaction between nitrones and cyclic a, p-unsaturated aldehydes, affording bicyclic adducts with high diastereoselectivity and enantioselec-tivity (Scheme 2.256) (759). 

The cyclization process can be promoted by using a single electron transfer mediator. Electron transfer from the mediator generates the carbonyl radical-ion away from the electrode surface so that cyclization can occur before there is opportunity for a second electron transfer. Thus reduction of 16, R = Me, in dimethyl-forraaraide at mercury in the presence of tetraethylammonium fluoroborate leads only to conversion of the ketone function to the secondaiy alcohol. However addition of a low concentration of N,N-dimethyl pyrrolidinium fluoroborate alters the course of reaction and the cyclized tertiary alcohol is now formed. This pyrrolidinium salt is reduced at -2.7 V vs. see at mercuiy to yield a complex DMP(Hg5) which is thought to act as a single electron transfer mediator [94]. Cyclization can... 

Succinimides, e.g., cis- and /ra .r-3,4-dimethylpyrrolidine-2,5-dione 1, show virtually the same behavior as their anhydride analogs the H-3 chemical shifts are 3.12 and 2.68 ppm, respectively 502. The pyrrolidinium salts 2 have been studied in mixtures of diastereomeric cis j trans pairs504. 

Synthesis of telechelic poIy(DMS) having pyrrolidinium salt groups... 

Table 1. Synthesis of Telechelic Poly(DMS) Having Hydroxyl (la, l a), Tosyl (lb, l b) and Pyrrolidinium Salt Groups (lc, l c)...

Thus a quantitative ion-exchange reaction was confirmed to take place by a simple precipitation of a THF solution of lc and l c into aqueous solution containing a benzoate anion, and the subsequent ring-opening reaction of the pyrrolidinium salt groups was found to proceed by the heating treatment at 100°C. 

Diastereoselectivity and enantioselectivity were observed to increase substantially when proline-derived diamine salts were used as organocatalysts. In particular, the pyrrolidinium salt 41-2HC1 was found to be very useful, furnishing the target molecule 38 in 70% yield with diastereoselectivity of d.r. = 95 5 and enantioselec-... 

Chlorotrimethylsilane with zinc in THF reduces 3-oxo-5 a-steroids directly to A2-olefinic derivatives, but most other oxo-groups are unreactive, allowing selective attack on the 3-oxo-group in diones.178 The 5)8-steroidal iminium perchlorate (204), obtained179 by reduction of the A4-unsaturated analogue with the Hantzsch ester (a dihydropyridine), can be reduced further with the same reagent to give the 3/3-pyrrolidinium salt (205) stereospecifically.180... 

We should also mention that simple nitrogen-containing derivatives of keto groups, such as 3-azo (D-150), 3-azine (D-5), and 3-hydrazone (D-15) derivatives, may also sometimes favorably affect the activity or the dissociation of activities, while others work in the opposite direction, such as 3-dimethylhydrazone (S-115,S-116) or 17-N-pyrrolidinium salt derivatives (E-15). 

In the next step a positively charged pyrrolidinium salt (C6o(C4HiqN+)) was probed, not only to overcome the Coulombic charge repulsion, but, more importantly, to attract a reaction with the hydrated electrons (Eq. 10) [90, 93, 94]. 

Because monofunctionalization of fullerenes shows that a single hydrophilic addend is insufficient to prevent the strong hydrophobic interactions among the compounds [89, 90, 93, 94], multiple functionalized derivatives were examined as water-soluble probes. In particular, introduction of a second hydrophilic ligand (e.g., pyrrolidinium salts or carboxylates) to the fullerene core enhances the surface coverage of the hydrophobic fullerene surface. In turn, it was expected that fullerene aggregation might be suppressed. It should be stated that these water-soluble derivatives are important alternatives to the y-CD-incorporated and surfactant-embedded fullerenes. 

A series of water-soluble bis-carboxylates and bis-pyrrolidinium salts (e.g. Ceo [C(COO )2]2 and C6o(C4HioN )2) were studied in aqueous solutions and compared... 

The first enantioselective organocatalytic 1,3-dipolar cycloaddition of acyclic nitrones with acrolein and crotonal-dehyde has been reported <2000JA9874>. In particular, the reversible formation of iminium ions from a,/3-unsatu-rated aldehydes and the enantiopure imidazolidinone 535 provided ( A-4-formylisoxazolidines in high yields and ees (Equation 86). A polymer-supported version of catalyst 535 was also prepared <2004EJ0567>. The catalytic performance of various chiral pyrrolidinium salts in the cycloaddition of 1-cycloalkene-l-carboxaldehydes was also evaluated <2003EJO2782>. 

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