4-Imidazolin-2-ones

Imidazolin-2-one, 1,5-diphenyl-4-aryl-synthesis, 5, 492 4-Imidazolin-2-one, 1-hydroxy-synthesis, 5, 474—475 4-Imidazolin-2-one, l-methyl-3-phenyl- C NMR, 5, 355 Imidazolinones acylation, 5, 424, 443 alkylation, 5, 443 developers... 

Imidazolin-2-ones polymers, 1, 296 synthesis, 5, 466, 491 Imidazolium cations, 2-fluoro-nucleophilic substitution, 5, 413 Imidazolium chloride, 4-amino-l-methyl-2,3-diphenyl-... 

A comparison of the reactivity of C-N or C-P fission in P-lactams and four-membered cyclic phosphonamidates, respectively, shows the latter to be much more reactive (95PAC711). The absolute configuration of some 1,3,4-trisubstituted P-Iactams is determined by CD spectra (95TL4217). A ring expansion of 3-amido-l-hydroxy-p-lactams to 4-imidazolin-2-ones by the action of tosyl chloride and organic base is reported (95TL1617). 

The reactions of 3-amido-l-hydroxyazetidin-2-ones 327 with />-toluenesulfonyl chloride in the presence of triethyl-amine provided the ring-expanded 4-imidazolin-2-ones 328 (Equation 114) <1995TL1617>. The key step in the mechanism of this reaction involved the ring opening by cleavage of the C(2)-G(3) bond, which is followed by double bond migration and an intramolecular nucleophilic addition of the amide nitrogen to an intermediate isocyanate. 

Thermal ring-closure of enecarbamoylazides (52) gives rise to 4-imidazolin-2-ones (Scheme 28) (7UHC557). 

The common reaction of an a-bromoketone with excess urea and ammonium acetate in aqueous acetic acid (refluxed for about 3 h) to give 4-imidazolin-2-ones in 50-75% yields can be simplifled and adapted to a single-flask process from the original ketones. The ketone is initially brominated at 18-20°C in a mixture of acetic acid and urea, then, after the addition of 30% ammonia solution, the a-bromoketone which forms is heterocycUzed in about 40% yield by further heating ( 3 h) [42]. 

The 3-alkyl, benzyl and phenyl derivatives of l-(2-hydroxy-4-bromophenyl)-3-methyl-4-imidazolin-2-one have been studied by solid-state C CPMAS NMR. The differences in chemical shifts A = 5(liquid) — 8(solid) are significant for aromatic carbons C3 ( — 2.9 ppm), C4 (3.6 ppm) and C5 (—3.9 ppm) and C7 (—1.5 ppm), which are adjacent to N1-C4, and are subject to the largest changes of the environment during reorientation of the imidazolin-2-one moiety. 

S-methylisothiourea (which is more correctly termed a substituted amidine) has already been mentioned above and elsewhere <8uoci30l>. Pyruvaldehyde reacts with ureas to form 4,5-dihydroxyimidazolin-2-ones which dehydrate to hydantoins <86JHCii25>, while benzil gives 4,5-diphenyl-4-imidazolin-2-ones ((241) R R = Ph) when heated with thioureas in acidic solution (Scheme 173) <9UCS(P2)1501>. Direct cyclocondensation of an a-bromoketone with urea forms around 50% of 2-imidazolinone when refluxed in ethylene glycol in the presence of an excess of... 

Little is known about the behavior of hydantoins in dissolving metal reductions. The reaction of hydantoin (132) with 5 equivalents of lithium in tert-butyl alcohol and liquid ammonia gives the 4-imidazolin-2-one 133. The use of methanol instead of r rt-butyl alcohol gives a mixture of reduced products, probably originated by ring cleavage as well as by reduction.325 ... 

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