Thiazole 5-ethyl-2-tert-butyl

H-1,3-Thiazin 2-Acetyl-2-ethoxy-carbonyl-3-ethyl-4-oxo-3,4-dihydrO- E14a/3, 529 (R2C = N2 4- 3-Oxo —2,3-H2 —1,2-thiazol) 1,2-Thiazol 3-tert.-Butyl-4,5-... 

Bis-[l,3-Benzothiazol-2-ylthio]-organo- 997 Bis-[4-tert.-butyl-1,3-thiazol-2-yl]- 71 Bis-[l,3-dimethyl-lH-pyrazol-5-yl]- 557 Bis-[4,5-diphenyl-l,3-thiazol-2-yl]- 71 Bis-[4-methyl-l,3-thiazol-2-yl]- 71 Bis-[5-nitro-l,3-thiazol-2-yl]- 244 Bis-[l,3-thiazol-2-yl]- 70, 71 Ethyl- 337... 

Acidic and basic hydrolysis of ethyl 4-oxo-4A-pyrido[l,2-a]pyrimidin-3-carboxylates gave 3-carboxylic acid derivatives (OlMIPl). Stirring tert-butyl ( )-3-(2-hydroxy-8-[2-(4-isopropyl-l,3-thiazol-2-yl)-l-ethenyl]-4-oxo-4Ff-pyrido[l,2-a]pyrimidin-3-yl)-2-propenoate in CF3CO2H at room temperature yielded ( )-3-substituted 2-propenoic acid. 

The effect of the halogen of the aryl halide was also carefully studied using bromobenzene and chlorobenzene as the electrophile. When the arylation was performed on ethyl 4-oxazole carboxylate using di-tert-butyl(methyl)phosphine as the Ugand and cesium carbonate as the base, the product of C5 arylation B was obtained when bromobenzene was used as the electrophile. Conversely, the product of C2 arylation A was formed if chlorobenzene was employed (eq 16). Similar results were obtained for the arylation of tert-butyl 4-thiazole carboxylate when mbidium carbonate was used as the base (eq 16). Again, it should be noted that the regioselectivity is highly dependent on the choice of the base and the phosphine. 

---