Oxazolines oxazolinium salts

The polymerization of 2-methyl-2-oxazoline is a clean reaction, which is not disturbed by chain transfer and termination. In this polymerization, the propagating species having the structure of an oxazolinium salt is not fragile, which is conveniently utilized for syntheses of block copolymers and end-reactive polymers [28],... 

Dideoxyhexopyrano[2, l-c/]oxazolines and respective oxazolinium salts, syntheses and reactions of 89MI33. 

Fragmentations of heterocycles have played an important role in the preparation of amide derivatives. Moderate to good yields of a-hydroxy-amides were obtained on reaction of a-hydroxy-acid aceto-nides with primary amines.N-Alkyl-2-methyl-2-oxazolinium salts (obtained by mixing alkyl halides and 2-methyl-2-oxazoline in dichloromethane) were found to react with sodium benzeneselenolate to yield -(2-phenylselenoethyl)-t -alkylacetamides, which after oxidation to ] -vinyl analogues with sodium metaperiodate in methanol, gave secondary amides on sequential treatment with mercuric acetate in aqueous tetrahydrofuran and sodium borohydride/3M... 

The synthesis and reactions of l,2-dideoxy-hexopyrano[2,l-d]oxazolines and oxazolinium salts have been reviewed. Acid-catalysed cyclisations of N-(glycos-2-yl)-urea and -thiourea derivatives have provided imidazolin-2-one and 2-thiazoline derivatives, e g. (76)-(78). 

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). 

N,4,4-Trimethyl-2-oxazolinium iodide is prepared by adding 49.5 g. (0.5 mole) of 4,4-dimethyl-2-oxazoline to an excess of cold methyl iodide (182 g., 80 ml., 1.28 moles) in a 500-ml. flask and stirring at room temperature under argon for 20 hours. The light brown solid is filtered with the aid of suction and then dissolved in 350 ml. of dry acetonitrile. The methiodide salt is precipitated by the addition of 750 ml. of dry ether to this acetonitrile solution. The purified salt is again filtered with the aid of suction, and the white solid is washed with 250 ml. of dry ether and finally dried under vacuum. This gives 96 g. (80%) of the methiodide, m.p. 215° (dec.). 

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