3-Acetylpyrrolidines

Rearrangement of allylic acetals. 3-Acetylpyrrolidines can be obtained in good yield by an acid-catalyzed rearrangement of 5-methyl-5-vinyloxazolidines. The rearrangement involves an aza-Cope rearrangement followed by Mannich cycli-zation (equation I).1... 

A comparison was made between the mechanisms of action of the PVC costabiliser N-phenyl-3-acetylpyrrolidin-2,4-dione and existing costabilisers. The results obtained demonstrated that the performance of short-term costabilisers in calcium/zinc formulations was linked to their ability to complex zinc stearate prior to the initiation of degradation and that this prevented the early formation of prodegradant zinc chloride. 6 refs. 

Acetylpyrrolidines may be prepared from 5-methyl-5-vinyloxazolidines via a reaction which involves a directed sigmatropic rearrangement as shown in Scheme 73. The procedure allows a ready synthesis of l-azaspiro[4,5]decanes." ... 

Chemoselective anodic methoxylation at a distinct carbon atom in the a-position to an amino group in a polypeptide was achieved by prior introduction of a silyl group as an electroauxiliary at this carbon atom [156]. Amide oxidation in A-acetylpyrrolidines substituted with electron-rich phenyl rings led to either methoxylation a to the nitrogen atom or in the benzylic position. Mechanistic studies indicate that both the amide and the phenyl oxidation compete, but intramolecular electron transfer leads to... 

A stereoselective total synthesis of dendrobatide toxin 251 D was developed by Overman et al.237) involving an epoxidation of the (S)-proline derivative (237) to furnish the oxirane (238) as major product. In their approach towards the total synthesis of the same natural product Thomas et al.238) investigated the stereoselectivity of the epoxide formation from (S)-5-acetylpyrrolidin-2-one and dimethyloxosulfonium methylide. A diastereoselectivity of d.s. 50-60% was achieved 238. ... 

The absolute configuration was also established unequivocally for C-8 of naturally occurring pyrrolizidine bases.88 It was demonstrated in the course of the structural analysis of isoheliotridene (146), obtained by degradation of the alkaloid monocrotaline, that ozonolysis of this compound affords 2-acetylpyrrolidine-l-acetic acid (147).66 The (— )-methyl ester of this acid was condensed with methylmagnesium iodide to give (— )-l-(2-hydroxy-2-methylpropyl)-2-(l-hydroxy-l-methylethyl)pyrrolidine (148). The same glycol (148) was obtained... 

The pyrrolidine amides (1-acetylpyrrolidine and 1-propionylpyrrolidine) are prepared from the appropriate acid chloride and pyrrolidine (Mansson and Westfelt 1980). 

Stock solutions of 1-acetylpyrrolidine, and an internal standard (1-propionylpyrrolidine or 1-methylnaphthalene) in dioxane at a concentration of 10 mg ml-1 are prepared. A mixture of 1ml each of the 1-acetylpyrrolidine and internal standard solutions is used to establish the GC response factor. The calibration is made by injecting a 2-/A aliquot of the mixture into the gas chromatograph and measuring the peak areas. 

The acetylated lignin, dissolved in 1.0 ml of dioxane containing 5 mg of an internal standard, is treated with 1.0ml of a dioxane-pyrrolidine (1 1, v/v) solution which initiates the aminolysis reaction. The rate of the 1-acetylpyrrolidine formation is followed by periodically injecting 1-2/d of the reaction mixture into the gas chromatograph. The initial rapid phase is generally complete within 20 min, but a total of 60min is required to complete the deacetylation process. 

Fig. 7.2.1A,B. Rate of formation of 1-acetylpyrrolidine on A aminolysis of acetylated wood meal Norway spruce and of methanol on B periodate oxidation of wood meal. (Lai et al. 1990)...

The rate of 1-acetylpyrrolidine formation is followed as in the case of acetylated lignin, but the overall process is much slower and a 6-7-h reaction period may be required as illustrated in Fig. 7.2.1A for Norway spruce wood meal. 

In addition to carbon-based radicals, other radicals such as sulfur-based radicals, generated from an RSH-type precursor (R = alkyl, acyl) with AIBN also smoothly added to allylglycine.4 Optimal results were obtained when both the unsaturated amino acids and RSH dissolved completely in the reaction medium (dioxane-water or methanol-water were found to be superior solvents). Radical additions of thiophenol to carbon-carbon multiple bonds and radical cyclisation of A-allyl-2-iodoalkanamide in aqueous media proceeded smoothly to the A-acetylpyrrolidine derivative in 96% yield. Under similar... 

Pyrrolidine Acetyl chloride A/-Acetylpyrrolidine (79%) Pyrrolidine hydrochloride... 

An interesting variation in the stereochemistry of addition of dimethyloxosulphonium methylide to 5-acetylpyrrolidin-2-one is produced by the addition of anhydrous ZnCl282. In the absence of the salt a 78 22 mixture of epoxides (47 a-Me) and (47 -Me) results, whereas, with added ZnCl2, this ratio changes to 23 77-... 

Furthermore, reduction of 1,4-anhydro-iminosugar 13 with sodium cyano-borohydride in acetic acid and deprotection in basic medium (Scheme 5) led to an equilibrium between N-acetylpyrrolidine 14 and 2-oxapyrrolizidine... 

When a benzene solution of complex 8 (0.1 mol%) containing pyrrolidine and ethyl acetate was refluxed under an argon atmosphere, quantitative conversion of pyrrolidine was observed by GC after 28 h, and N-acetylpyrrolidine was isolated in 98% yield (Table 1.10, entry 1). The same results were obtained when the reaction was carried out in refluxing toluene. The scope of the ester amidation reaction was explored with various esters and amines, and the results are summarized in Table 1.10. 

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