2.5- Dimethyl-5-phenyl-2-oxazoline

In contrast to the above additions A-allyl- and substituted A-allyl-amides, -urethanes, -ureas and -thioureas undergo intramolecular cyclization only in 6(3-96% sulfuric acid to give the corresponding oxazolinium and thiazolinium salts. Treatment of these cations with base yields 2-oxazolines and 2-thiazolines in moderate to good yields. The reaction is illustrated by the conversion of A-2-phenylallylacetamide (342) into 2,5-dimethyl-5-phenyl-2-oxazoline (343) in 70% yield 70JOC3768) (see also Chapter 4.19). 

Carbonyl alkylation and condensation reactions are always of great value in synthesis, and the formation of o-ANIS ALDEHYDE via 4,4-dimethyl-2-oxazoline, 2,2-DIMETHYL-3-PHENYLPROPION-ALDEHYDE via alkylation of the magnesio-enamine salt and threo-4-HYDROXY-3-PHENYL-2-HEPTANONE via a directed aldol... 

By contrast, (4-methylphenyl)[2-(4,4-dimethyl-2-oxazolin-2-yl)phenyl]-bismuth 7/-(trifluoromethanesulfonyl)amide (5) is prepared in quantitative yield by the action of a 1 1 molar mixture of potassium tert-butoxide and trifluoromethanesulfonyl amide (TfNH2) on chloro(4-methylphenyl)[2-(4,4-dimethyl-2-oxazolin-2-yl)phenyl]bismuthine in THF at room temperature [98OM1013]. In contrast to amide 4, the amide 5 is thermally stable and does not disproportionate when stood in a solution. 

The novel concept of elaboration of unactivated olefins by nucleophiles has been reported. Nucleophilic attack is initiated by reaction of the olefin with dimethyl(tnethylthio)sulphonium fluoroborate (4) and, in conjunction with nitrogen nucleophiles, a high degree of regiocontrol is observed in an azasul-phenylation reaction (Scheme 7), the products of which not only permit an overall olefin amination, but also an oxazoline synthesis, a m-hydroxyamination, and an aziridine synthesis. The analogous selenium reagent, dimethyl(phenyl-seleno)sulphonium fluoroborate, p-phenylselenates a variety of anilines in moderate yield. ... 

Oxazoline, 2-alkenyl-polymerization, 1, 282 2-Oxazoline, 2,5-dimethyl-5-phenyl-synthesis, 5, 141 Oxazolines... 

Phenyl-A2-oxazolin-4-one forms the furan (282) on treatment with dimethyl acetyl-enedicarboxylate. The reaction may be interpreted as proceeding through a Diels-Alder addition to the tautomeric oxazole (281) (Scheme 74) (72CC1000). 

Heine and co-workers693 prepared the adduct 5 from 2,2-dimethyl-4-phenyl-6-p-nitrophenyl-1,3-diazabicycIo [3,1,0]hex-3-ene (4) and DEAD in refluxing xylene acid hydrolysis gave (7). The aroylaziridine 6 with DEAD also gave 7 (14%), as did the oxazolin-5-one 8 and DEAD via the benzylpyrrole 9. 

The best known of the potential mercaptoimidazoles are the imidazoline-2- and benz-imidazoline-2-thiones, which resemble imidazolin-2-ones in that the tautomeric form (53 X = S) is the preferred form. The crystal structure and the HNMR spectrum of 1,3-dimethyl-3H-imidazoline-2-thione have been interpreted as showing partial double bond character in the N—C—N system, but no aromaticity (70CC56). However, the preference for a betaine structure (56) rather than (57) or (58) should be accepted with caution since it is really only a resonance structure similar to others which undoubtedly contribute to the overall structures of oxo-, thio- and amino-imidazoles. Measurement of the piSTa values for a series of imidazoline-2-thiones substituted variously on C-4, C-5, N-1 and N-3 by hydrogen, phenyl or methyl shows that all of the values are similar. Approximate Kr values calculated show that these compounds exist even more in the thione forms (53, X = S 58) than do the corresponding thiazoline-2-thiones and oxazoline-2-thiones. The UV spectra in aqueous solution support thione structures, as do dipole moment and X-ray studies (76AHC(S1)280, p. 400). 

The photochemistry of more complex and highly substituted alkenic partners has been studied. In 1978, Hartmann and coworkers reported the photocycloaddition of 4-oxazolin-2-one with acetone, used as a photosensitizer in the reaction of 4-oxazolin-2-one with alkenyl and alkynyl partners, to form oxe-tane (44). Recently, Scharf has described the photochemistry of 3-acetyl-2,3-dihydio-2,2-dimcthyloxa-zole (45). Irradiation of (45) in the presence of acetophenone produced the oxetane (46) with the phenyl group endo (17%), in addition to 21% of a ring-opened derivative. The stereoselectivity is in agreement with the high exo carboxyl selectivity observed in the photocycloaddition of methyl phe-nylglyoxylate with 2,2-dimethyl-1,3-dioxole to produce oxetane (47). 

Soloshonok and Hayashi applied chiral ferrocenylphosphine-gold(I) complexes to asymmetric aldol-type reactions of fluorinated benzaldehydes with methyl isocyano-acetate (27) and A, A/-dimethyl-a-isocyanoacetamide (95). It is noteworthy that successive substitution of hydrogen atoms by fluorine in the phenyl ring of benzaldehyde causes gradual increase of both the cis selectivity and the ee of cw-oxazolines [53]. 

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... 

Benzonitrile isopropylide, generated from 2,2-dimethyl-3-phenyl-2//-azirine, undergoes a cycloaddition reaction to the ester carbonyl group of diethyl (ethoxycarbonyl)phosphonate to give the diethyl 5-ethoxy-2,2-dimethyl-4-phenyl-3-oxazolin-5-ylphosphonate in 96% yield. ... 

The 2-oxazolin-S-ones are excellent acylating agents for a variety of enzymes. Thus, 2-phenyloxazolin-5-one and 4,4-dimethyl-2-phenyl-2-oxazolin-S-one react with a-chymotrypsin, trypsin, and papain to form stable acyl enzymes.15-18 The azlactone from p-nitrobenzoylvaline reacted with a-chymotrypsin and trypsin, and it was observed that the enzymic activity of chymotrypsin decreased with increasing number of p-nitrobenzoylvaline residues.19 The reaction of a-chymotrypsin with 2 has been studied extensively.20-25 In this reaction, the oxazolone dis-... 

With dimethyl fumarate, methyl acrylate, and methyl methacrylate as dipolarophiles, substituted pyrrolines are obtained.52-54 In contrast, the reaction of 2-phenyl-2-oxazolin-5-onium perchlorate with benzyl-ideneaniline follows a different course to give the imidazolin-4-one (24).55... 

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