Thiazole 2-methyl-5-ethyl

Thiazole, methyl-5-propyl-Thiazole, 2-butyl-Thiazole, 2-ethyl-Thiazole, 2-ethyl-5-methyl-Thiazole, 2-methyl-Thiazole, 2-(3-methylbutyl)-Thiazole, 2-(1-methylethyl)-Thiazole, 2-(1-methylpropyl)-Thiazole, 2-(2-methylpropyl)-Thiazole, 2,4-diethyl-Thiazole, 2,4-dimethyl-Thiazole, 2,4,5-trimethyl-Thiazole, 2,5-diethyl-4-methyl-Thiazole, 2,5-dimethyl-Thiazole, 4-ethyl-2-methyl-Thiazole, 4-ethyl-5-methyl-Thiazole, 4-methyl-... 

Thiazole itself can be obtained by condensing chloroacetaldehyde and thioformamide (Scheme 159). The reaction is explosive and proceeds in low yield because of the instability of the thioformamide under acid conditions. Higher thioamides are more stable and react under milder conditions with chloroacetaldehyde, affording 2-substituted thiazoles in moderate yields. It is possible, and often preferable, to prepare the thioamide in situ in dioxane solution by the action of phosphorus pentasulfide on the corresponding amide and in the presence of solid MgC03 (Scheme 160). With arylthioamides, except for some nitrothiobenzamides, yields are usually higher and the cyclization is carried out over several hours in boiling absolute alcohol. Chloroacetaldehyde can be replaced in these reaction by derivatives such as 1,2-dichloro- or dibromo-ethyl methyl or ethyl ether, 1,2-dichloro- or dibromo-ethyl acetate, 2-chloro- or dibromo-ethyl acetate, and 2-chloro or bromo-diethyl-acetal. 

Thiazole, 4-(2-methylpropyl)-Thiazole, 4-propyl-Thiazole, 4,5-dimethyl-Thiazole, 5-ethyl-Thiazole, 5-ethyl-2,4-dimethyl-Thiazole, 5-ethyl-2-methyl-Thiazole, 5-ethyl-4-methyl-Thiazole, 5-methyl-... 

To a cooled (0 °C) solution of thiazole ethyl ester 14 (450 mg, 0.88 mmol) in dry MeOH (4.5 mL) was added NaOMe (153 mg, 2.82 mmol). After stirring for 5 h at 0 °C, the reaction mixture was quenched with saturated NH4CI solution (50 mL), and the resulting mixture was extracted with EtOAc (2 x 50 mL). The combined organic layers were washed with brine (50 mL), dried (MgS04) and concentrated. Purification of the residue by flash column chromatography (silica gel, hexanes/EtOAc, 6 4) afforded thiazole methyl ester 15 (320 mg, 91%) as a white foam. 

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). 

German or Japanese authors name these dyes (3-ethyl-4,5-diphenylthiazole-2)(3-ethylrhodanine-5)-0-methine neutrocyanine and (3-methyl-4,5-diphenyl thiazole-2)(3-methyl-l-p-sulfophenyl-2-pyrazol-5-one-4)tetramethineneutrocyanine, respectively. 

Rhodacyanines possess two chromophoric systems. They are at the same time neutrocyanine derivatives, which involves position 5 of the ketomethylene, and methine cyanine, which involves position 2. Following lUPAC s standard nomenclature rules, structure 7 is named 3-ethyl-4-phenyl-2- 4-oxo-3-ethyl-5-[2-(3-ethy]-2,3-dihydro-benzo-l,3-thiazo-lylidene)ethylidene]-tetrahydro-l,3-thiazolylidene-methyl -1.3-thiazolium iodide (Scheme 5). It implies that the 4-phenyl thiazole ring having the... 

Potts et al. (333) condensed dipolarophiles (DMA, dibenzoylacetylene, ethyl propiolate) with ylides (81) obtained by quaternization of 4-methyl-thiazole with an a-bromoketone or ester and subsequent deprotonation. In fact the 1 1 molar adduct obtained (82) rearranged to a pyr-rolothiazine (83). One example of this reaction is described Scheme 49. 

Similarly, ethyl (or methyl) a-formyl chloroacetate (69), Rj = H, and its substituted derivatives, condensed with thioformamide or higher thioamides give 5-ethyl- or 5-rnethyl-thiazole carboxylates (70) in good... 

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). 

Ethyl-cf-chloroacetoacetate gives 5-carbethoxy-4-methyl-2-thiazole thiol (387), while 3-chloro-2,4-pentanedione affords the 2-mercapto-4-methyl-5-thiazolylmethylketone in good yield (74%) (387). 

R 2-R Thiazole 2-R-4-Methyl- ihiazole 2-R-4-Ethyl-thi azole 2-R-4-i-PropyI- thiazolc 2-R-4-i-Butyl- thiazole... 

Hydrolysis of ethyl 4-methyl-2,5-thiazole dicarboxylate (9) or dicar-boxylic acid dichloride gives an excellent yield of 4-methyl-5 thiazole carboxylic acid (10) instead of the dicarboxylic acid (Scheme 6). This lability is a general Property of 2-thiazolecarboxylic acids. 

Reduction with sodium in alcohol was unsuccessful (54). The introduction of lithium aluminium hydride has provided an elegant method for the reduction of thiazole esters to hydroxythiazoles for example, ethyl 2-methyl-4-thiazolecarboxylate (11 with lithium aluminium hydride in diethyl ether gives 2-methyl-4-(hydroxymethyl)thiazole (12) in 66 to 69% yield (Scheme 7) (53),... 

The Claisen condensation of an aliphatic ester and a thiazolic ester gives after acidic hydrolysis a thiazolylketone (56). For example, the Claisen condensation of ethyl 4-methyl-5-thiazolecarboxylate with ethyl acetate followed by acid hydrolysis gives methyl 4-methyl-5-thiazolyl ketone in 16% yield. 

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

Thiazole, 5-ethyl-2-methyl-kinetic data, 6, 255 (68CR(C)(266)714)... 

Thiazole-5-carboxylic acid, 4-methyl-ethyl ester... 

This procedure is representative of a new general method for the preparation of noncyclic acyloins by thiazol ium-catalyzed dimerization of aldehydes in the presence of weak bases (Table I). The advantages of this method over the classical reductive coupling of esters or the modern variation in which the intermediate enediolate is trapped by silylation, are the simplicity of the procedure, the inexpensive materials used, and the purity of the products obtained. For volatile aldehydes such as acetaldehyde and propionaldehyde the reaction Is conducted without solvent in a small, heated autoclave. With the exception of furoin the preparation of benzoins from aromatic aldehydes is best carried out with a different thiazolium catalyst bearing an N-methyl or N-ethyl substituent, instead of the N-benzyl group. Benzoins have usually been prepared by cyanide-catalyzed condensation of aromatic and heterocyclic aldehydes.Unsymnetrical acyloins may be obtained by thiazol1um-catalyzed cross-condensation of two different aldehydes. -1 The thiazolium ion-catalyzed cyclization of 1,5-dialdehydes to cyclic acyloins has been reported. 

Prior to the 1947 report by Cook and Heilbron on their novel synthesis, 5-aminothiazoles were mostly unknown in the literature. Previous syntheses included the Curtius degradation of ethyl thiazole-5-carboxylates which did not have general applicability there was also difficultly in obtaining the necessary starting materials. During a study on penicillin, Cook and Heilbron found that the reaction between methyl dithiophenylacetate and ethyl aminocyanoacetate gave what was initially believed to be ethyl phenylthionacetamidocyanoacetate 4. However further studies proved the compound to be 5-amino-4-carbethoxy-2-benzyl-thiazole 5, which was basic. 

Vilsmeier-Haack formylation of 2-(4-methyl-l-piperazinyl)-4//-pyrido-[l,2-n]pyrimidin-4-one with a mixture of POCI3 and DMF at 95°C gave a 3-formyl derivative (93FES1225) while ethyl 4-oxo-6,7,8, 9-tetrahydro-4//-pyrido[l,2-n]pyrimidine-2-acetate at 50 °C yielded a 9-dimethylaminomethylene-3-formyl derivative (01MI4). 3-Formyl-2-hydroxy-8-[2-(4-isopropyl-l,3-thiazol-2-yl)-l-ethenyl]-4//-pyrido[l,2-n]pyri-midin-4-one was obtained from the 3-unsubstituted derivative with oxalyl chloride-DMF reagent in CH2CI2 at room temperature for 3h (OlMIPl). 

Fig. 7 Structures of the dyes forming aggregates on DNA (a) l-methyI-4-[[3-methyl-2(3//)-benzothiazolylidene]methyl]-quinolinium (Thiazole Orange, TO), (b) 3,3 -diethyIthiadicarbo-cyanine (DiSC2(5)), (c) 3,3 -trimethylammoniopropylthiadicarbocyanine (DiSC3+(5)), (d) 2- [(Z)-2-(2,5-dihydro-2-thienyl)-3 - [3 -methyl-2(3/f)-benzothiazolylidene] -1 -propenyl] -3 -methyl -benzothiazol-3-ium (L-21), (e) 2-[( )-3-[3,7-diethyT6-[( ,2 )-3-(l-ethyl-3,3-dimethyl-3/7-indo-lium-2-yl)-2-propenylidene]-6,7-dihydrothiazolo[5,4-/]benzothiazol-2(3//)-ylidene]-l-propenyl]-l-ethyl-3,3-dimethyl-3//-indolium (BCD), (f) 3-methyl-2-[( )-3-methyl-2-[[3-methyl-2(3/f)-ben-zothiazolylidene]methyl]-l-butenyl]-benzothiazol-3-ium (Cyan ]3iPr)...

Care must be taken in the choice of organic solvent. Chloroform should never be used under the basic conditions due to the risk of the formation of isocyanides (see Chapter 7) and the use of carbon disulphide can lead to formation of dithiocarba-mates, e.g. dimethyl A -(ethoxycarbonylmethyl)iminodithiocarbonate is formed (35-39%), as the major product in high purity, in the liquiddiquid two-phase methyl-ation of ethyl glycinate in carbon disulphide [15]. The product is useful as an intermediate in the synthesis of thiazoles [15] and dihydrooxazoles [16]. 

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