3-Thiazolines, synthesis from ketones

The synthesis of 3-thiazolines from ketones requires that the latter is treated neat or in dry solvents (3). The presence of water diminishes the yield however. 3-Pentanone with aqueous sodium polysulfide in the presence of ammonia gave an 18% yield (after correction for recovered ketones) of 3-thiazoline but under anhydrous conditions, an 85% yield (13). 

Synthesis of thiazolines from ketones, sulfur and NH3 with the possibility to obtain thioketones. 

Asinger zl -thiazoline ring synthesis from 2 ketone molecules... 

The production of substituted thiazolines from ketones, sulphur, and ammonia under restrained conditions is well documented. - Asinger et have successfully employed ethyleneimine as one of the reactants in this versatile synthesis. Thus, slow addition of sulphur to a mixture of ethyleneimine and diethyl ketone, heptan-4-one, or an alicyclic ketone at ca. 20 °C yields 5,6-dihydro-4JT-l,4-thiazines (284) as main products (60—90%) and 2,2-dialkylthiazolidines (285) as by-products (10— 23%). ... 

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. 

In addition to ester enolates, ketone enolates and nitronates also add to 3-thiazolines in the presence of BF3 Et20. Reactions of ketone enolates have been cleverly exploited in the synthesis of 2,3,5-trisub-stituted thiophenes (260) by hydrolysis of adducts (259) and spontaneous cyclization to liberate water and ammonia (Scheme 52 Table 30). The 5-substituent of the thiophene is derived from the 5-substi-... 

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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