2-oxazolinium salts

Electrochemical reduction of oxazolinium salts 36 gives the anions 37, which add efficiently to alkyl halides or, in the presence of McsSiCl, to methyl acrylate, methyl vinyl ketone, and acrylonitrile. Simple acid hydrolysis then gives the ketone products 38 and 39, and this method is quite general since the starting salts are readily prepared from carboxylic acids, R C02H (87TL4411). 

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],... 

The electroreduction of oxazolinium salts gives acylanion equivalents that react in a Michael addition with activated olefins as shown for methylacrylate in Scheme 145 [263]. 

Scheme 145 Cathodic Michael addition of an oxazolinium salt.

Reduction of IV-alkyl iminium salts also ought to afford radical-derived products. Indeed, reduction of oxazolinium salts (31) results in isolation of the corresponding dimers, which can in turn be converted to the corresponding benzils by acid hydrolysis33 (equation 14). In a similar vein, electrochemical reduction of IV-butenyl iminium salts (32) affords cyclopentane derivatives (equation 15)34. 

When the A-ethylnitrilium salt 35 reacts with pinacolone 117, it gives the N-acyliminium intermediate 302 (equation 83) which can undergo a retropinacol rearrangement to yield the 2-oxazolinium salt 30386. 

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

The oxazolinium salts 40 (isomeric form of the corre nding tertiary oxonium salt) formed according to Eq. (40) are in equilibrium (because of the high nucleo-philicity of the bromide anion) with the corresponding alkyl bromide ... 

Oxazoles have also been used to generate azomethine ylides in intramolecular [3+2] cycloadditions with alkynes <2000JA5401 1 he nucleophilic attack of cyanide ion on the oxazolinium salt 75 led to the formation of azomethine... 

Reduction of oxazolinium salts in DMF yields the anion of the tetrahydro-oxazole, which may be used as an acyl anion equivalent [278]. 

The C-2 to C-1 participation of iV-acetyl and iV-benzoyl groups in sugars has been reported by Micheel and coworkers. The 2-acetamido-2-deoxy-D-glucose derivative (156) rearranged to the amine salt (157), simply on keeping a solution in water or acid an oxazolinium salt such as... 

The synthetic utility of this method is increased by intercepting the oxazolinium salts with various nucleophiles to prepare lactams that bear an (o-fiinctionalized carbon chain. It is also possible to form azacycles containing a 2-dicyanomethylene group. Direct reduction of the oxazolinium salts with NaBH gives amines. ... 

A2-oxazolinium salts, electrochemical generation 43, 585 -, Michael addition with - 43,603... 

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... 

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