2-Phenyl-2-oxazoline

The application of this strategy to the synthesis of chiral cyclohexadienes has been demonstrated by Kiindig. Addition of MeLi to the Cr(CO)3-complexed chiral phenyl oxazoline 43 followed by reaction with allyl bromide produced cyclohexadiene 44 in 69% yield and >98% de. ... 

Single crystals of 1 1 complex. °1 1 Catalyst obtained by evaporation of CH2CI2. After 3 months in an open air. Ligand (Ff,Ff)-isopropylidene-2,2 -bis(4-phenyl-oxazoline). Anhydrous complex catalyst prepared from NIBr2 and AgSbFg. 

In 1994, the same authors reported the synthesis of corresponding oxazolines tethered to sulfoxides by ortholithiation of the parent 2-phenyl oxazoline with butyllithium followed by addition of either (5)- or (/ )-/ -tolylmenthyl-sulfinate. Applied as ligands in the test reaetion, these diastereomerie ligands gave very different results, as shown in Seheme 1.25, thus demonstrating the... 

Gu, R.-L., Lee, I.S. and Sih, C.J., Chemo-enzymatic asymmetric synthesis of amino acids. Enantioselective hydrolyses of 2-phenyl-oxazolin-5-ones. Tetrahedron Lett., 1992, 33, 1953-1956 Crich, J., Brieva, R., Marquart, P., Gu, R.-L., Flemming, S. and Sih, C.J., Enzymic asymmetric synthesis of a-amino acids. Enantioselective cleavage of 4-substituted oxazolin-5-ones and thiazolin-5-ones. J. Org. Chem., 1993, 58, 3252-3258. 

For conversion of functionalized diorganozincs into tertiary amines, aromatic compounds which contain a directed metallation group, such as Af,Af-dialkylbenzamides, methoxymethyl phenyl ether, phenyl oxazolines and phenyl Af,Af-dialkylcarbamates, were ortho-lithiated, transmetallated and then aminated with 2a in good yields, but with a slower reaction rate (Scheme 19). 

The efficient phase-transfer-catalyzed alkylation strategy with le was successfully applied by Jew and Park to the asymmetric synthesis of a-alkyl serines, using phenyl oxazoline derivative 53 as a requisite substrate [28]. The reaction is general, however, and provides a practical access to a variety of optically active a-alkyl serines through acidic hydrolysis of 54 (Scheme 5.26). 

Typical Procedure for the Catalytic Asymmetric Benzylation of Phenyl Oxazoline Derivatives [67] (p. 144)... 

Figure 64. 01igo(thiophene)s bearing chiral />phenyl-oxazoline side chains. 

Solvent effects are essentially free-energy correlations [57] and we shall omit in this chapter those of strongly acidic media as these are clearly not pertinent to biochemistry. The effect of variation of solvent on a rate or equilibrium constant may be treated in the same way as a substituent effect. We may apply the same criteria to elucidate mechanistic or rate-determining step changes to free-energy relationships with solvent effects. Let us consider the hydrolysis of 5-phenyl-oxazoline-2-ones... 

Die aus der Reaktion von (1) und Benzonitriloxyd isolierten Produkte (37—40) lei ten sich alle von der hypothetischen Zwischenstufe (41) ab. Mit einem zweiten Mol (1) entsteht 3-Phenyl-oxazolin-l,2 (37) durch Cyclisierang und Phenyl-vinylketon-oxim (38) durch Eliminierung. Aus (38) gehen durch Addition weiteren Nitriloxyds die Oxime (39) und (40) hervor. 

This reaction has been modified by using either phenyl oxazoline or substituted benzaldehyde and nitroethane as the starting materials for preparing isoquinoline. 

In 2005, Park and coworkers reported a synthetic strategy for obtaining a-allqrlserines with phenyl-oxazoline tert-butyl ester 19 by catalytic allgflation... 

Among the potentially bidentate, P,N ligand derivatives of quite different structure can be found. The electronic and steric parameters of 2-(2 -diarylphosphino-phenyl)oxazoline-type ligand, PHOX) (81) may be varied both... 

Oxazoline was shown to be an efficient directing group for arylation of arene derivatives with Ru(II) catalyst [(Eq. 5)] [61], A -Acylimidazole was also shown to be a directing group promoting ortho monoarylation of arene. Ort/io-alkenylation of 2-phenyl oxazoline with alkenylbromide was performed using the same mthe-nium(II) catalyst [61]. 

Jaroch, S., Matsuoka, R.T., and Overman, L.E. (1999) Studies towards a total synthesis of sarains A-C. Stereospecific condensation of a.P Unsaturated esters with the phenyl oxazoline derivative of threonine. Tetrahedron Lett., 40,1273-1276. 

Jew, Park, and coworkers extended the substrate scope of phase-transfer catalytic alkylation to the oxazoline system in order to synthesize chiral a-alkyl serine derivatives. The authors chose phenyl oxazoline derivative 74 [106] as the substrate (Scheme 12.6). In the presence of Cj-symmetric chiral quaternary ammonium bromide (S,S)-31c, the asymmetric phase-transfer alkylation of 74 with alkyl halides, followed by acidic hydrolysis, provided chiral a-alkyl serines in very high yields and enantioselecti vities. 

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). 

Furo[3,4-d]oxazoline, cis-tetrahydro-2-phenyl-synthesis, 6, 1017 Furopyrans, 4, 993-995 Furopyrazines, 4, 988 Furo[2,3-6]pyrazines synthesis, 4, 988... 

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

The first synthesis and use of a chiral oxazoline was reported by Meyers in 1974. The chiral oxazoline 1 was prepared in two steps by condensation of (-i-)-l-phenyl-2-amino-1,3-propanediol (6) with the ethyl imidate of propionitrile followed by 0-methylation of the resulting alcohol 7 with NaH/Mel. Meyers demonstrated chiral oxazoline 1 could be... 

The mechanism of the asymmetric alkylation of chiral oxazolines is believed to occur through initial metalation of the oxazoline to afford a rapidly interconverting mixture of 12 and 13 with the methoxy group forming a chelate with the lithium cation." Alkylation of the lithiooxazoline occurs on the less hindered face of the oxazoline 13 (opposite the bulky phenyl substituent) to provide 14 the alkylation may proceed via complexation of the halide to the lithium cation. The fact that decreased enantioselectivity is observed with chiral oxazoline derivatives bearing substituents smaller than the phenyl group of 3 is consistent with this hypothesis. Intermediate 13 is believed to react faster than 12 because the approach of the electrophile is impeded by the alkyl group in 12. 

A more expected difference between platinum oxide and palladium-on-carbon was found in the hydrogenolysis of 5-phenyI-2-(3,4-dimethoxybenzyI)-2-oxazoline. Cleavage occurred at the benzyl-oxygen bond over both catalysts, but over platinum, the less substituted phenyl group was saturated as well (78). 

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

---