Oxazoles, hydro

Porif.> (hydro)pyrimidine, macroQ clic and oligomeric pyridine or pyridinium, naphthyridine, oxazole, pteridine, pyridoacridine, pyrrole, pyrroloimiiMquinone, (oxa)quinoli2idine, terpenoid indolizidine. ISOPR. Monotero. rare Sesouitem. . Ditero.. Sestertero. also degraded C>i Tritero.. POLYKET. macrolides, polyacetylenes, polycyclic (hydro)quinones, polyethers, (epidioxy)polyp ionates. ... 

Malonamid-ale 4-Fluoro-a-[(hydro-xymeihylamino)-benzyliden]-E15/1.682 (aus dcm 4.5-H, — 1,2-oxazol/hr)... 

A solution of 5.1 grams 2-chloro-4,5-diphenyl-oxazole, 6.3 grams diethanolamine and 50 ml absolute ethanol was refluxed for 4 hours. The solvent was stripped at 1 mm and the oily residue was added at 60°C to 100 ml 50% ethanol by cooling the hydro-alcoholic solution, 4.5 grams of 2-bis((3-hydroxyethyl)amino-4,5-diphenyl-oxazole was obtained (yield, 69.5%). The product crystallized from ethyl ether + petroleum ether, with a MP of 96 to 98°C. 

Furo(3,4-c)pyridin 7-Hydroxy-6-methyl-1,3-dihydro- -Hydro-chlorid E7b/2, 533 [4-CH3-1,3-oxazol -(- 3-(S02 —CH3)... 

Allylacetoxime, —When aliow ed to react with mercuric acetate this compound yields an hydro-iso-oxazole derivative. 

Of the 1,3-azoles, oxazoles are the most easily reduced, catalytic sequences also bringing about C-0 bond cleavage. 1,3-Azolium salts are easily attacked by hydride reducing agents thiazolium salts produce tetra-hydro derivatives (24.1.2.6). ... 

Benzo-l,3-oxazol 566, 1123, 1323 6-Anilino-5-hydroxy-4-acetyl- 980 6-Dimethylamino-5-hydro v-3,4,7-tnmethyl-2.3-dihv-dro- 979.980 2-Hydruxy- 577... 

D hydro-l,3-oxazol-<2-sp ro-3)-cyclobutan-< l-spiro-2>-2,5-dihydro-1.3-oxazol... 

Die Uberfuhrung dieser 5-Oxo-4,5-di hydro-1,3-oxazol-Derivate (ungesattigten Azlac-tone) in freie a-Amino-carbonsauren erfordert drei Reaktionsschritte ... 

Reactions of Oxazoles. 2-Amino-4-methyloxazole (359) forms the rearranged hydro-peroxide (360) by the action of hydrogen peroxide. Thermolysis of 2- (3,3-di-methylallyloxy)-4,5-diphenyloxazole yields the oxazolin-2-one (361) with inversion of the allyl group by [ , ] sigmatropic shift irradiation, on the other... 

The use of oxazole-alkene Diels-Alder cycloadditions to form biologically relevant molecules has recently been applied to the synthesis of isoindoles, useful intermediates for the preparation of substance P antagonists. Thus 5-ethoxy-4-methyloxazole 8 reacted with 4,4-dimethyl-2-cyclopentenone 78 in refluxing benzene in the presence of catalytic zinc bromide to give the (l//)-cyclopenta(c)-pyrrole 80 as a separable 3 1 mixture of cis and trans isomers in 53% yield (Fig. 3.22). The reaction is presumed to proceed via the intermediacy of cycloadduct 79. When cyclohexenone 81 was used as the dienophile, the product was the hydro-(l//)-isoindole 82, obtained via dehydroformylation of the cycloadduct, in 85% yield after only 30 min in refluxing benzene. 

Lacton der 2 [9-Oxy 10ben2oes4ure 27, 230. 2.5.5 Triphenyl oxazol( i-(4) 27, 230. CtjH NOsS ae-[ aphthyl-(2) 8ulfon]>/7-s1yTyl> acryls ure-ziitril 10, 320. 2t ylmercapto>anthrachinoii 14 1502,... 

As an alternative to the ambident reactivity of nitroso partners, the dual nucle-ophilicity of hydroxylamines has been exploited for the seleetive construction of valuable functionalized hydro-oxazoles. Efficient entries to these heterocyclic building blocks have been developed following two eomplementary direetions involving either aza- or oxa-Miehael addition in the first step. Thus, Cordova and coworkers proposed a simple and effieient chemo and enantioseleetive aeeess to 5-hydroxyisoxazolidines 58 based on i minium activation of unsaturated aldehydes with diphenylprolinol silyl ether as the organoeatalyst (Scheme 2.16). The domino reaetion is initiated by an aza-Michael addition of N-protected hydroxylamines 56 to the iminium ions, and... 

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