Carbonates cyclization

Diethyl oxalate functioned as one-carbon rather than two-carbon cyclizing agent with the diamino-heterocyclopyrimidines 37 to give the triazo-lopyrimidines 38. Diethyl malonate, ethyl acetoacetate, or ethyl... 

Cyclization of 1,2,4-Triazoles Having a -C-C-N Appendage at C3 with One-Carbon Cyclizing Agents... 

Hydrazine 835 underwent ring closure with one carbon cyclizing reagents to afford 837 and/or /V-acyl derivatives 836. The N-acyl derivatives underwent cyclization on treatment with phosphorus oxychloride. They were also prepared by the reaction of hydrazones 838 with thionyl chloride (84JHC1565). Compound 835 underwent ring closure with carbon disulfide and ethyl chloroformate to give 839 (Scheme 169). 

Quinoxalinethione carrying 2-hydroxyethyl substituent at C-3 carbon cyclizes by trifluoroacetic anhydride to produce 2,3-dihydrothieno[2,3- ]quinoxalines 123 (Equation 24) <2003S2799>. 

Alternatively, pyrrolof 1,2-c]quinazoline (63) was prepared through formation of the pyrimidine ring by cyclocondensation of 2-(2-amino-phenyl) pyrrole precursors (e.g. 62) with one-carbon cyclizing agents (69MI1). 

Mercaptoquinazoline 247 was cyclized with three-carbon cyclizing agents such as 1,3-dibromopropane (73JMC633 84JIC1050 85AP502),... 

This annulation has invariably been made by reaction of 3-amino-1,2,4-triazole derivatives with three-carbon cyclizing fragments. The three-carbon fragments may be incorporated in one step or in two consecutive steps as schematically represented in Schemes 26 and 27, respectively. 

Chloroacetaldehyde oxime, 2-carbon cyclization using, 55, 287 N-Chloroamides, chlorinating agents for pyrroles, 57, 326 N-Chloroamines radical cyclizations from, 58, 19 radicals by photolysis of, 58, 10 Chlorocarbonylsulfenyl chloride, reaction with 5-aminouracils, 55, 153 Chlorodimethylsulfonium chloride,... 

A variety of one-carbon cyclizing agents have been used (71JOC10) to prepare 3-substituted l,3-thiazolo[2,3-c] 1,2,4-triazoles (111) from 2-hydrazino-l,3-thiazoles (110). The acid hydrazides (113) of these hydrazines, prepared either directly from 110 and carboxylic acid derivatives or indirectly from 1-acylthiosemicarbazides (112) and a-haloketones, also undergo facile dehydrative cydization to 111. [71JOC10 78JHC401 ... 

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