Imidazolidine ring opening

Lithium tetrahydridoaluminate sodium hydroxide Reductive imidazolidine ring opening... 

Condensation reactions of aromatic aldehydes with a,cu-polyamines lead to Schiff bases, if the polyamine involved contains only primary amino groups or to imidazolidines, if the polyamine contains a secondary amino group. Condensation of 2-pyridinecarboxaldehyde 7V-oxide with triethylenetetramine yields derivative (31), with two imidazolidine rings, which in the presence of Cu11 undergoes a ring-opening reaction due to the formation of a complex.42... 

Imidazolidine ring closure and opening Modified Curtius degradation... 

Hydroxy-5,6-dihydrodibenzo[a, ]quinolizin-8-ones (321) were obtained from protonated 9b-hydroxyimidazo[4,3-fl]isoindol-5-ones (319) <85JCR(S)35l>. The mechanism proposed for this reaction comprises an acid-promoted ring opening of the imidazolidine unit, followed by opening of the diazocine (320) and final cyclization with loss of ammonia and formaldehyde (Scheme 72). 

Mercuric acetate ethylenediaminetetraacetic acid Oxidative N-ring opening Aminoaldehydes s. 28, 92 monoacyl-1,2-diamines from imidazolidines cf. H. Mohrle and C.-M. Seidel, M. 107, 51 (1976)... 

Tamm and coworkers [98] overcame the tendency for this FLP to form the abnormal NHC-borane adduct through the C4 carbon by using a saturated analog of the NHC. The same hydrogen activation and THF ring-opening reactions were observed for the imidazolidin-2-ylidene as shown in Scheme 15.6. 

The much-studied tetraaminoethylene (5) is oxidized slowly, but even at room temperature, by elemental sulfur to yield 1,3-diphenyl-imidazolidine-2-thione (70a, 85%) . The same transformation has been reported for aliphatic peraminoethylene (32), giving 70b . Again the simplest reasonable interpretation ofthese events is expressed by equations (6-9), where the initial step is nucleophilic attack on the Sg ring, with ring opening. Initiation by electron transfer from the ethylene to sulfur, however, is also an attractive possibility. 

When 3-benzoylimino-5,6-dihydro-37f-imidazo[2,l-c][l,2,4]dithiazole (19) is treated with methanol or ethanol in the presence of sodium hydroxide 0-alkyl-A-[2-(2-alkyl-l-benzoyl-3-iso-ureido)ethyl]thiocarbamates (119) are formed as a result of the opening of both rings. Under analogous conditions the reaction with n-propanol affords imidazolidine-2-thione (120) and the sodium salt of Y-benzoyl-O-propylcarbamate (121) (Scheme 5) <868751 >. 

On the other hand, a so-called cleavage of the imidazolidine 5-ring of 7 led to the efficacy of the open-chain 12, which is higher than that of ACh or 7 on the SADyS2 hybrid nAChR expressed in X. oocytes. The super agonist action of 12 and related ligands may account for the more potent action of 12 than that of 7 on a wide range of insect pests [200]. 

On the other hand, the sterically forbidden regions beyond the imidazolidine 3-nitrogen atom of 11 is important for binding [72]. The area around the 6steric interactions were more important for open-chain neonicotinoids than ring systems. 

Finally, it was also shown that the open-chain neonicotinoids bind to the nAChR recognition site in a similar manner to ring structures like 11, and that the electrostatic properties of the open[Pg.978]

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