Thiazole, 2-acetyl

Acetyl Thiazole 127.17/C5H5NOS/ colorless to pale yel liq/ s—prop glycol, veg 1 mL in 1... 

Acetyl Thiazole 645 Black Pepper Oil 662 Cinnamyl Butyrate... 

Acetaldehyde Diethyl Acetal 2-Acetyl Thiazole Allyl Phenoxy Acetate Allyl Propionate Borneol... 

Appendix V), 104 Acetyl Methyl Carbinol, 64 2-Acetylpyrrole, 64 2-Acetyl Thiazole, 64, 94... 

Acetyl Thiazole, 94 Allyl Phenoxy Acetate, 95 Allyl Propionate, 95 Aspartame-Acesulfame Salt, 96 Borneol, 96... 

DIMETHYL-TRISULFIDE 2JSO-BUTYL THIAZOL 44ylETHYL VINYL THIAZOLE 2-ACETYL THIAZOLE... 

Thiazoles 2-acetyl thiazole imparts a roasted, crusty (bread crust, meat crust) note. Trimethyl thiazole has a nutty, green, cocoa note. 

Thiazoles and pyrazines have somewhat similar sensory properties. Pittet and Hniza [54] and Ho and Jim [63] have reported that the alkylthiazoles give green, nutty, roasted, vegetable, or meaty notes. Trimethyl thiazole is reported to have a cocoa, nutty character. 2-isobutyl thiazole is one of the best known thiazoles and has a strong, green odor of tomato leaf This compound is considered to be important to tomato flavor. 2,4-dimethyl-5-vinyl thiazole has a nut-like odor. 2-acetyl thiazole is characterized as having a nutty, cereal, and popcorn flavor [47],... 

Further syntheses of KDO (26) have appeared. Dondoni and coworkers have used 2-acetyl thiazole as a pyruvate synthon in a stereospecific reaction with an a Idehydo-D-arahinose derivative (Scheme 7),31 whilst in another... 

This characteristic feature appears to be required for a roasted odor. In fact, aU the pyrroUnes and pyridines listed in Table 5.23 as weU as 2-acetyl-thiazole, 2-acetylthiazoline (cf. Table 5.22) and acetylpyrazine (cf. Table 5.23) contain this structural element and have a roasted or cracker-hke odor. However, the thresholds of these compounds vary greatly. The lowest values were found for 2-acetyl-and 2-propionyl-l-pyrrohne. The length of the alkanoyl group also influences the aroma activity because in the transition from 2-propionyl- to 2-hutanoyl-l-pynoline, the roasted note suddenly disappears and the odor threshold increases hy several powers of ten. 2-Acetyl-l-pyrrohne (Apy) is responsible for the typical aroma of the cmst of white bread and it... 

Chapter V. Quinaldine (V,2) 2-methyl-, 2 5-dimethyl- and 2-acetyl-thiophene (V,8-V,10) 2 5-dimethyl and 2 4-dimethyl-dicarbethoxy-p3nrole (V,12-V,13) 2-amino- and 2 4 dimethyl-thiazole (V,15-V,16) 3 5-dimethyl-pyrazole (V,17) 4-ethylp3rridine (from pyridine) (V,19) n-amyl-pyridines from picolines) (V,28) picolinic, nicotinic and isonicotinic acid (V,21-V,22) (ethyl nicotinate and p-cyanop3n idine (V,23-V,24) uramil (V,25) 4-methyl-(coumarin (V,28) 2-hyi-oxylepidine (V,29). 

Reduction of 2.4-dimethyl-5-nitrothiazole with activated iron gives a product that after acetylation yields 25% 2.4-dimethyl-5-acetamido-thiazole (58). The reduction of 2-methyl 5-nitrothiazole is also reported (351 to give a mixture of products. The nitro group of 2-acetylhydrazino-5-nitrothiazole is reduced by TiCl in hydrochloric acid or by Zn in acetic acid (591. 

The general pattern of alkylation of 2-acylaininothiazoles parallels that of 2-aminothia2ole itself (see Section III.l). In neutral medium attack occurs on the ring nitrogen, and in alkaline medium a mixture of N-ring and N-amino alkylation takes place (40, 43, 161. 163). In acidic medium unusual behavior has been reported (477) 2-acetamido-4-substituted thiazoles react with acetic anhydride in the presence of sulfuric acid to yield 2-acetylimino-3-acetyl-4-phenyl-4-thiazolines (255) when R = Ph. but when R4 = Me or H no acetylation occurs (Scheme 151). The explanation rests perhaps in an acid-catalyzed heterocyclization with an acetylation on the open-chain compound (253), this compound being stabilized... 

Various 4-, 5-, or 4,5-disubstituted 2-aryIamino thiazoles (124), R, = QH4R with R = 0-, m-, or p-Me, HO C, Cl, Br, H N, NHAc, NR2, OH, OR, or OjN, were obtained by condensing the corresponding N-arylthiourea with chloroacetone (81, 86, 423), dichloroacetone (510, 618), phenacyichloride or its p-substituted methyl, f-butyl, n-dodecyl or undecyl (653), or 2-chlorocyclohexanone (653) (Method A) or with 2-butanone (423), acetophenone or its p-substituted derivatives (399, 439), ethyl acetate (400), ethyl acetyl propionate (621), a- or 3-unsaturated ketones (691), benzylidene acetone, furfurylidene acetone, and mesityl oxide in the presence of Btj or Ij as condensing agent (Method B) (Table 11-17). 

Acetyl-3-mercaptopropanol reacts with acetaldehyde in the presence of hydrazine hydrate to yield 2,4-dimethyl-5-(/3-hydroxyethyl)thiazole (10), R, = Rj = Me, R3 = CH2CH2OH (556). 

Robba and Le Guen (91) have shown that 4,5-dicyanothiazole and various Grignard reagents react partially to give 4-acetyl-5-cyano-thiazoles. As previously mentioned, the cyano group in the 5-position is the least reactive. 

The Clemmensen reduction of 2-acetyl-5-methyl thiazole gives 2-ethyl-5-methyl thiazole (31) (Scheme 37). 

Although in general azoles do not undergo Friedel-Crafts type alkylation or acylation, several isolated reactions of this general type are known. 3-Phenylsydnone (120) undergoes Friedel-Crafts acetylation and Vilsmeier formylation at the 4-position, and the 5-alkylation of thiazoles by carbonium ions is known. 

Thiazole, 4-acetoxymethyl-2-methyl-synthesis, 6, 254 Thiazole, 2-acetyl-occurrence, 6, 327... 

Thiazole, 4-methyl-5-(2-hydroxyethyl)-in thiamine biosynthesis, 1, 97 Thiazole, 4-methyl-2-methylami nosynthesis, 6, 300 Thiazole, 4-methyl-2-phenyl-alkylation, 6, 256 mercuration, 6, 256 Thiazole, 2-(methylthio)-methylation, 6, 290 thermodynamic values, 6, 291 Thiazole, 2-methylthio-5-phenyl-synthesis, 5, 153 Thiazole, 4-methyl-5-vinyl-occurrence, 6, 327 Thiazole, 2-phenyl-acetylation, 6, 270-271 Conformation, 6, 237 synthesis, 5, 113, 6, 306 Thiazole, 4-phenyl-conformation, 6, 237 2,5-disubstituted synthesis, 6, 304 Thiazole, 5-phenyl-conformation, 6, 237 Thiazole, 2-phenyl-5-triphenylmethyl-synthesis, 6, 265 Thiazole, 2-(2-pyridyl)-metal complexes, 5, 51 6, 253 Thiazole, 4-(2-pyridyl)-metal complexes, S, 51 6, 253 Thiazole, tetrahydro-ring cleavage, 5, 80 Thiazole, 2,4,5-trimethyl-occurrence, 6, 327... 

As demonstrated above, nitro derivatives of five-membered heterocycles have found extensive use as antiinfective agents. It is therefore of interest that the nitro derivative of a substituted thiazole was at one time used as an antitrichomonal agent. Bro-mination of 2-aminothiazole (136) (obtained from condensation of thiourea with chloroacetaldehyde) gives the 4-bromo derivative (138) this is then acetylated to 139. Treatment of 139 with nitric acid leads to an interesting displacement of bromine by a nitro group to afford aminitrazole (140)... 

Another antiulcer histamine Hj receptor antagonist containing a thiazole moiety is zalb-dine (131) Its synthesis can be accomplished readily by brominating 4 acetyl 2 methylimidazole (129) to give haloketone 130 Displacement with amidinothiourea completes the synthesis of zaltidme (131) via a displacement cyclodehydration sequence [45]... 

In the case of a diketone (e.g., 3-tosyloxypentane-2,4-dione), the formation of 5-acetyl-4-methyl-2-aryl-l,3-thiazole derivatives can be realized in very good yields (86-89%) (Scheme 7). All these experiments where performed in a Sears Kenmore unmodified household microwave oven (990 W) equipped with a turntable. The average bulk temperature was estimated by inserting a thermometer in the alumina bath housing the reaction vessel. 

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