5-methyloxazole

NMR data for 4-methyloxazole have been compared with those of 4-methylthiazole the data clearly show that the ring protons in each are shielded. In a comprehensive study of a range of oxazoles. Brown and Ghosh also reported NMR data but based a discussion of resonance stabilization on pK and UV spectral data (69JCS(B)270). The weak basicity of oxazole (pX a 0.8) relative to 1-methylimidazole (pK 7.44) and thiazole (pK 2.44) demonstrates that delocalization of the oxygen lone pair, which would have a base-strengthening effect on the nitrogen atom, is not extensive. It must be concluded that not only the experimental measurement but also the very definition of aromaticity in the azole series is as yet poorly quantified. Nevertheless, its importance in the interpretation of reactivity is enormous. 

C4H5NO 693-93-6) see Pyridoxine 4-methyloxazole-S-carboxamide (C5H4N2O2 4866-00-6) see Pyridoxine 2-methyi-4-(oxiranylmethoxy)-ltf-indole (Ci.H.jNOa 62119-47-5) see Bopindolol Mepindolol (2S-7ranj)-(2-methyl-4-oxo-3-azetidinyl)carbamic acid 1,1-dimelhylethyl ester (C9H14N2O3 80582-03-2) see Aztreonam... 

By lithiation of 4-methyloxazole with n-BuLi and subsequent quenching with trimethyltin chloride, Dondoni et al. prepared 2-trimethylstannyl-4-methyloxazole [18], which was then coupled with 3-bromofuran to provide the expected furylthiazole. 

In 1987, Yamanaka s group described the Pd-catalyzed reactions of halothiazoles with terminal acetylenes [22a]. Submission of 4-bromo- and 5-bromo-4-methyloxazoles to the Sonogashira reaction conditions with phenylacetylene led to the expected internal acetylenes. 

Amino-3-methylisoxazole, 1502 2-Amino-4-methyloxazole, 1500 5-Amino-3-methylthio-l,2,4-oxadiazole, 1192 Ammonium A-nitrosophenylaminooxide, 2399 2-Aza-l,3-dioxolanium perchlorate, 0898 Azoformaldoxime, 0815 Bis(l-benzo[d]triazolyl) carbonate, 3598 Bis(l-benzo[d]triazolyl) oxalate, 3629 Bis(trifluoromethyl) nitroxide, 0638 2-/er/-Buty 1-3 -phenyloxaziridine, 3406 Calcium bis(O-hydroxylamide). 3930 Calcium hydroxide O-hydroxylamide, 3929... 

Diels-Alder reactions.2 This vinyl sulfone has been used as an acetylene equivalent in a new synthesis of vitamin Be. Thus 1 undergoes a Diels-Alder reaction with 4-methyloxazole (2) to give a pyridoxine derivative (3) with elimination of mcthanesulfinic acid. The product is converted into the vitamin (4) in three simple steps. 

Oxazoles may be similarly prepared in good yields. Thus, 5-ethoxy-4-methyloxazole (173) was obtained by treating ethyl 2-formamide propionate (172) with phosphorus pentoxide in chloroform at 55°C (72JCS(P1)909,914). Known collectively as the Robinson-Gabriel synthesis, these cyclodehydrations can be effected by sulfuric acid or anhydrous hydrogen fluoride (cf CHEC 4.18). 

The following standard esterification procedure was applied to /V-benzoylalanine oxalyl chloride was added to a solution of /V-benzoylalanine in anhydrous THF, the mixture was stirred overnight at room temperature, then the solvent and residual traces of oxalyl chloride were evaporated in vacuo. Triethylamine and then methanol were added to the residue at 0°C. On work-up, none of the expected amino acid ester was obtained. The product, isolated in 51% yield, was found to be methyl 2-phenyl-4-methyloxazole-5-carboxylate, and the process was found to be general for a variety of IV-benzoylated a-amino acids. 

See Hydrogen peroxide 2-Amino-4-methyloxazole See related ISOXAZOLES... 

The ESIPT of 2-(2 -hydroxyphenyl)-4-methyloxazole (HPMO) (27) has been explored by Douhal and co-workers [166] for its probe characteristics in a variety of organized media which include cyclodextrin, calixarene, micelle, and HSA. The incorporation of HPMO into hydrophobic cavities in an aqueous medium involves the rupture of its intermolecular hydrogen bond to water and formation of an intramolecular hydrogen bond in the sequestered molecule. Upon excitation (280-330 nm) of this entity, a fast intramolecular proton-transfer reaction of the excited state produces a phototautomer (28), the fluorescence of which (Xm = 450 170 nm) shows a largely Stokes-shifted band. Because of the existence of a twisting motion around the C2—C bond of this phototautomer, the absorption and emission properties of the probe depend on the size of the host cav-... 

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