4- Aminothiazoles with benzaldehyde

This nucleophilic reactivity of 2-aminothiazoles has been used to prepare biheterocyclic compounds. Thus 2-aminothiazole reacts with chlorovinyl methyl ketone yielding 5-methyl-thiazolo[3,2-a]pyrimidinium chloride (Scheme 109). In the presence of formaldehyde, aminothiazoles react with ends affording condensation products, through the intermediacy of Mannich bases (Scheme 110). In acidic medium and at higher temperatures, condensation of 4-aryl-2-aminothiazole with benzaldehyde takes place at the C-5 position (Scheme 111). The same orientation is observed when 2-amino-4-methylthiazole is alkylated by secondary or tertiary alcohols in 85% sulfuric acid (Scheme 112). 

By condensing carbon oxysulfide with o-aminOnitriles the corresponding 2-hydroxy-5-aminothiazoles can be obtained. In the presence of benzaldehyde or its substituted derivatives the reaction leads to 5-benzy-lideneaminothiazole derivatives (218) in good yields (Scheme 114 and Table 11.35) (393, 442). However, the reaction fails with or-amino acetonitrile (206), R = H (317). The 2-alkoxy analogs (220), R = Me, Et, Pr, Bu, vinyl, were similarly obtained from 219 and benzylideneamino acetonitrile (Scheme 115a) (393). 

Barium thiocyanate, 118 Base catalysis, 34 in acylations, 47, 48 of chelate formation, 95 of clevage, 128 of cydization, 127 in hydrolysis, 115 Basicity, of 2-aminothiazole, 90 of 2-imino-4-thiazolines, 124 Beckmann rearrangement, of oxime, 16 Benzaldehyde, with alkyl-acetamidothi-azole, 46... 

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