1-Substituted 4-ethoxycarbonyl-5 pyrazoles

Chelated species are less common. The substituted thiourea 7V-ethoxycarbonyl-/V-[3-(/>-anisyl) pyrazol-5-yl]thiourea (eatu) acts as a monoanionic 0,S-chelate to cobalt(II), forming Co(eatu)2.506 Whereas ethylenethiourea (etu) has been observed to act as a S-donor monodentate in Co (etu)2X2(H20)2 (X = C1, Br), it binds as an S,N-chelate in Co(etu)2(OOCCH3)2.507 Both violet octahedral and blue tetrahedral cobalt(II) compounds Co(pptu)2Cl2 and Cp(pptu)Cl2 respectively were prepared with bidentate A -2-(5-pico 1 y 1)- A"-pheny 11hiourea (pptu) chelated.508 Refluxing Co powder with thiourea in 4-methylpyridine provides a route to isothiocyanates, which form by decomposition of thiourea to ammonium thiocyanate509 with one product, Co(pic)4(NCS)2, characterized by a crystal structure. 

The reaction of differently substituted 5-arylidenehydrazono-4-ethoxycarbonyl-3-methyl-(l/7)pyrazoles 194 (X = 2-NC>2, 4-NC>2, 2-Cl, 4-Me, 4-NMe2, 2-OMe) with bromine in acetic acid in the presence of sodium acetate leads mainly to 3-aryl-7-ethoxycarbonyl-6-methyl-(li/)pyrazolo[5,l-c][l,2,4]triazoles 195 (Scheme 7) <1977J(P1)2047>. 

The 3 + 2-cycloaddition of commercially available MeaSiCHNa with camphor sultam-derived dipolarophiles produces 3-trimethylsilyl-substituted-A -pyrazolines which on acid treatment convert into optically active A -pyrazolines. The nucleophihc addition of ethyl diazoacetate with iV-ethoxycarbonyl-7V (2,2,2-trichloroethyhdene)a-mine produces a new diazo intermediate (35), which by 1,3-dipolar cycloaddition followed by a sigmatropic rearrangement of the cycloadduct (36) fiimishes a substituted pyrazole (37) (Scheme 13).. ... 

Diethyl acetone-l,3-dicarboxylate (1) reacts with N,N-dimethylforma-mide dimethyl acetal (DMFDMA) in ethanol at room temperature to give diethyl l-dimethylamino-3-oxobut-l-ene-2,4-dicarboxylate (2), which was used without isolation and purification. To this mixture 1 equivalent of a monosubstituted hydrazine was added and then stirred at room temperature or heated under reflux for several hours to form intermediates 3, which were, without isolation, cyclized into 1-substituted 4-ethoxycarbonyl-5-(ethoxycarbonylmethyl)pyrazoles 4 in 24-71% yield (08ACSil019) (Scheme 1). 

There are many methods for the synthesis of pyrazolopyrimidines (02SOS(12)613, 84CHEC(5)305, 96CHEC-II(8)365, 08CHEC-III(11)551). With diethyl l-dimethylamino-3-oxobut-l-ene-2,4-dicarboxylate (2) and aminoguanidine, first a substitution intermediate 42 is formed, which cyclizes into pyrazole 43, followed by cyclization into the bicyclic 7-amino-2-ethoxycarbonyl-lH,2H-pyrazolo[2,3-c]pyrimidin-5-one (44). The intermediates 42 and 43 were not isolated (08ACSil019) (Scheme 16). 

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