2-Phenyl-2-oxazolines

Phenylmercunc chlonde, conversion to phenyltnchloromethylmercury by reaction with sodium tn-chloroacetate 46, 98 2 Phenyl 2 oxazolin-5 one, 47,... 

The discovery of oxazoline hydroxamates as potential inhibitors of LpxC was the result of high-throughput screening of large libraries of compounds at the Merck Research Laboratories in collaboration with the Department of Biochemistry, Duke University Medical Center [95]. The lead compound, L-573,655, was a racemic mixture of 4-carbohydroxamido-2-phenyl-2-oxazoline, which had been previously made by Stammer et al. [96] as a precursor in the chemical synthesis of cyclosporine. Namely, (R,S)-serine methyl ester hydrochloride (149) is converted into (R,S)-4-carbomethoxy-2-phenyl-2-oxazoline (150) via treatment with ethyl benzimidate using the Elliot procedure [97]. Treatment of this ester with one equivalent each of hydroxylamine and sodium methoxide in methanol at room temperature affords the desired (R,S)-4-carbohydroxamido-2-phenyl-2-oxazoline (151), as depicted in Scheme 30. 

Fig. 9.30 a) Normalized MALDI TOF mass spectrum of all fractions (taken after 2 h to 72 h of polymerization time) of poly(2-phenyl-2-oxazoline) freed by dissolving the gold core with NaCN solution and collection of the polymer. The calculated mass of the monomer unit (147.17) is in good agreement with the spacing of the mass signals (AM = 146.93) of the most prominent peaks. Based on ear-... 

Hoogenboom R, Fijten MWM, Schubert US (2004) The effect of temperature on the living cationic polymerization of 2-phenyl-2-oxazoline explored utilizing an automated synthesizer. Macromol Rapid Commun 25 339-343... 

Michael Reaction. 5(47/)-Oxazolones undergo base-catalyzed conjugate addition to activated unsaturated compounds to afford the corresponding C-4 Michael adducts. For example, base-catalyzed addition of a 4-monosubstituted-5(4//)-oxazolone 157 to methyl propiolate yields a mixture of diastereomeric methyl 3-(5-oxo-2-phenyl-2-oxazolin-4-yl)acrylates 158. Hydrolytic ring opening of 158 and subsequent oxidation with lead tetraacetate affords 3-acylacrylates 160... 

The requisite 2-aryl-2-oxazolin-4-ones can be synthesized using the procedure briefly described by Gordon for the preparation of 2-phenyl-2-oxazolin-4-one (65a)53K The method utilizes an intramolecular O-alkylation of an imide ambident anion. 

The lack of reactivity of the aryloxazolinones (65) in photocycloaddition to many of the olefins other than 1,1-dimethoxyethene and furan probably results from efficient decay of E2 or D. Exciplex E2 and diradical D are proposed as intermediates in these cases for several reasons. Exciplex formation is most likely dependent on olefin ionization potential, and the ionization potential of many of the un-reactive olefins are intermediate between the ionization potential of furan and 1,1-dimethoxyethene as determined from the maxima of tetracynoethylene olefin charge transfer bands60 66,67. Although ds-2-butene does not form a cycloadduct with 2-phenyl-2-oxazolin-4-one (65a), ds-2-butene is isomerized to rram-2-butene during the irradiation52. Cis-trans isomerization is expected from decay of a triplet diradical. Decay of the exciplex and diradical intermediates in competition with reaction presumably results from steric hindrance from the aryl substituent. The olefins which give cycloadducts, furan and 1,1-dimethoxyethene, are expected to produce low steric hindrance with the aryl substituent in an exciplex or diradical. 

Cl 1 HI20 1-phenyl-1-penten-3-one 3152-68-9 535.65 47.320 2 21967 C11H13NO 4,4-dimethyl-2-phenyl-2-oxazoline 19312-06-2 521.82 45.984 2... 

In a variation of this synthetic method 2-phenyl-2-oxazoline-5-one is treated with heterocyclic amines in refluxing tetrahydrofuran to give 6, which on cyclization gives the corresponding 5-heteroarylamino-2-phenyloxazole.61... 

Recently, very high-molecular-weight. polyEI was prepared by acid hydrolysis of polymer formed from 2-phenyl-2-oxazoline. According to viscosity measurements (r)sp/c = 0.15 1 g-1) the authors claim Mw = 350000 68). 

Kagiya et al. determined the reactivity ratios of 2-phenyl-2-oxazoline (Mx) in copolymerization with other substituted oxazolines in N,N-dimethylacetamide at 135 °C19). The reported values of r2 and r2 are collected in Table 15.4 l/rt (= k12/kn) and... 

Table 15.4. Reactivity ratios in the copolymerization of 2-phenyl-2-oxazoline (M,) 19)...

Preliminary results indicate the possibility of preparing ABA block copolymers containing polyacetal (as a middle block) and polyamine blocks 121). When N-t-butylaziridine or 2-phenyl-2-oxazoline are added to a solution of living polyDXP, further polymerization ensues and the products have considerably higher molecular weights than the original polyDXP. NMR analysis confirmed the block character of the product. 

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