Thiazolines, aldehyde synthesis

Thiazoline, trans-2-amino-4,5-dimethyl-synthesis, 6, 310 2-Thiazoline, 2-aryl-synthesis, 6, 307, 308, 309 2-Thiazoline, 2-arylamino-tautomerism, 6, 248 2-Thiazoline, 2-dialkylamino-synthesis, 6, 308 2-liiiazoline, 5-imino-synthesis, 5, 461 2-"niiazoline, 2-mercapto-hydrolysis, 6, 272 oxidation, 6, 272 synthesis, 6, 307 2-Thiazoline, 2-methyl-aldehyde synthesis from, 1, 469 2-Thiazoline, 2-methyl-acetylation, 6, 270 acylation, 6, 270 H NMR, 6, 243... 

The ion 133 also reacts with epoxides to form y-hydroxy aldehydes after reduction and hydrolysis,and with aldehydes and ketones (16-41). Similar aldehyde synthesis has also been carried out with thiazoles " and thiazolines (five-... 

Of all the methods described for the synthesis of thiazole compounds, the most efficient involves the condensation of equimolar parts of thiourea (103) and a-haloketones or aldehydes to yield the corresponding 2-aminothiazoles (104a) or their 2-imino-A-4-thiazoline tautomers (104b) with no by-products (Method A, Scheme 46). 

As opposed to ketones, the same low-temperature action of sulfur and ammonia on aldehydes received very little attention presumably because the results of the initial exploration discouraged utilization in synthetic chemistry. Again in reference to unpublished work, the product mixture was claimed to contain 3-thiazoline, formed in 10% yield (3). The low-temperature synthesis of aldehyde-generated thiazolines (2, Rj = R2 = H), as depicted in Figure 1, possibly may have some geochemical interest when viewed in the Tight of reports that such thiazolines are dehydrogenated to thiazoles by sulfur at 130 6C ( -10). 

The photochemical addition of 2H-azirines to the carbonyl group of aldehydes, ketones and esters is completely regiospecific (77H143). Besides the formation of the isomeric oxazolines 18 from 3 and ethyl cyanoformate, there is also formed the imidazole 19 from addition to the C = N in the expected regioselective manner. Thioesters lead to thiazolines 20, while isocyanates and ketenes produce heterocycles 21 (Scheme 4). The photocycloaddition of arylazirines with a variety of multiple bonds proceeds in high yield and provides a convenient route for the synthesis of five-membered heterocyclic rings. Some of the dipolarophiles include azodicarboxylates, acid chlorides, vinylphospho-nium salts and p-quinones. 

Syndiesis of aldehydes. Meyers ei al. have described a method for synthesis of aldehydes similar to one using 2,4-dimethylthiazole (this volume). It is illustrated here for the synthesis of 2-(l-hydroxy)cyclohcxylacctaldehyde (5). The thiazoline (1) is treated in THF under nitrogen at —78° with a slight excess of n-butyllithium. The resulting lithiothiazoline is then treated with cyclohexanone first at —78° and then at... 

Startg. aldehyde allowed to react with 2-phenyl-2-thiazolin-5-one in tetrahydro-furan in the presence of basic lead acetate product. Y 11%. - This is a stage in a total synthesis of dl-Terramycin, a tetracycline derivative. H. Muxfeldt et al.. Am. Soc. 90, 6534 (1968). 

The highly stereoselective synthesis of ( )-a,P-unsaturated amides bearing (5)-a-methylbenzylamine has been achieved from readily available 2-phosphona-mides via Horner-Wadsworth-Emmons (H-W-E) reaction. " A broad range of substituted dihydropyrimidines (222) and thiazolines can be efficiently prepared using a four-component reaction involving phosphonates, nitriles, aldehydes and... 

The synthesis of trans-3-acyl- 3-lactam methyl esters 107 has been reported by Almqvist and coworkers [81, 82] by the Staudinger reaction of ketenes, generated from the Meldrum s acids 105, with methyl (i )-thiazoline-4-carboxylate 106 in benzene in the presence of hydrogen chloride (Scheme 3.36). An exceptionally low yield of 38% was obtained in the reaction of acetylketene. These esters could then be selectively reduced to the corresponding aldehydes 108 in moderate yields using diisobutylaluminum hydride (DIBAL-H). The Meldrum acids are well-known precursors of ketenes [83, 84]. They undergo a pericyclic reaction under thermal influence to generate ketenes with the release of carbon monoxide and acetone. 

A new synthesis of aldehydes with 2-methyl-2-thiazoline has the advantage of releasing the aldehydes from the thiazolidine intermediate under neutral conditions . Acetylene derivatives can be obtained from aldehydes via dibromomethylene compounds Novel reactions of alkynes with cationoid electrophiles have been published. -Diketones and 2-ketoalkoximes can be obtained by this reaction from acid chlorides and aliphatic nitro compounds respectively Addition of aldehydes to activated carbon-carbon double bonds occurs smoothly in the presence of cyanide ions as catalysts . Poly- -carbonyl compounds have been prepared by condensation of two anions, whereby the enolate salt of a y8-keto ester condenses as an electrophilic anion with strong nucleophiles such as the dianion of benzoylacetone. ... 

Lithium derivatives of 2-substituted A -thiazolines continue to be of interest in synthesis. Thus the organolithium compounds (70 R = H or Ph), prepared by metallation of 2-methylthio- or 2-benzylthio-AMhiazoline, react with aldehydes or ketones R R CO to yield the corresponding carbinols, which are useful because they decompose on being heated, or in the presence of base, to give episulphides (70a) in high yields. A -Thiazolines have been employed to prepare aldehydes, as shown in Scheme 1. A major feature of this process is... 

Hantzsch s synthesis of A -thiazolines, like that of thiazoles (see this voL, p. 567), has been shown to involve isolable intermediate 4-hydroxy-hetero-cycles. A series of 3,4-dialkyl-A -thiazoline-2-thiones (162) were prepared from N-alkyldithiocarbamates and a-halogeno-ketones or -aldehydes in this work the stereochemical course of this reaction was elucidated (see... 

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