4- Methylene-2-imidazolinones

Propargyl alcohol (332) and (328) react readily with isocyanates in the presence of a basic catalyst to give 4-methylene-2-oxazolidinones (334) and 4-methylene-2-imidazolinones (336), respectively (63JOC991). In the absence of sodium methoxide the intermediate methanes (333) and ureas (335) were obtained and on treatment with sodium methoxide underwent ring closure. Moderate to excellent yields were obtained. 

The target molecule contains an imidazolinone off of the C4, Cg positions. This heterocycle can be formed by adding a molecule of urea to an alpha-bromoketone. Accordingly, intermediate 18 would be brominated with a radical process using Nbromosuccinimide in methylene chloride,25 then urea would be added under acetic acid conditions to give the new heterocycle. Ammonium acetate in acetic acid would then complete the hexacyclic intermediate 21. ... 

The diester 23 was hydrolyzed to diacid 24, and then dehydrated to give anhydride 25. Subsequent reaction of this anhydride with amino amide 26 in acetonitrile gave two regioisomeric acid diamides 27 and 28 in the approximate ratio of 10 to 1. Pure 27 was isolated in 85% yield by heating the mixture in methylene chloride followed by extraction with 5% aqueous NaOH at room temperature. Treatment of 27 with 5% aqueous NaOH at 80 C then led to cyclization forming the desired imidazolinone 5. Its structure was confirmed by spectroscopic data and elemental analysis. 

Azacoumarins, e.g., 41, represent possible intermediates to the phenyl-substituted pyrano[2,3-b]pyridines. Thus, Perkin reaction of the acetylpyridone 15 with phenylacetic acids formed azacoumarins in fairly good yields. Attempts to reduce the carbonyl function of the lactone ring to the methylene function were unsuccessful. Nevertheless, the imidazolinones 42 derived from these azacoumarins were synthesized. 

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