in Wiley Online Library (wileyonlinelibrary.com).Electrophilic heterocyclization of 5-alkenyl-1-methyl-6-thioxopyrazolo [3,4-d]pyrimidin-4-ones and 3alkenyl-2-thioxoquinazoline-4-ones under the action of p-alkoxyphenyltellurium trichloride leads to annulation of thiazoline cycle with formation of 7-[(p-alkoxyphenyl)telluromethyl]-1-methyl-6,7dihydropyrazolo[3,4-d][1,3]thiazolo[3,2-a]pyrimidin-4(1H)-ones hydrochlorides and 2-(p-alkoxyphenyl) dichlorotelluromethyl-2,3-dihydro-5H-[1,3]thiazolo[2,3-b]quinazolin-5-ones hydrochlorides. Reduction of salts by the action of excess of sodium sulfite leads to formation of arylhetaryl telluride. in 20 mL of triethylamine. The reaction mixture was refluxed for 2 h. Precipitate was filtered and washed by methanol. The product was crystalized from ethanol. 3-Prop-2-en-1-yl-2-thioxo-2,3-dihydroquinazolin-4(1H)-one(6). Yield 61%; white powder (ethanol); mp. 203-205°C; mp. 201°C [18]; IR (KBr): (v/см À1 ) = 1648 (C═O); 1 H NMR (400 MHz, DMSO-d 6 ): δ (ppm) 12.94 (s, 1H), 7.92 (d, J = 8.0 Hz, 1H), 7.72 (t, J = 7.8 Hz, 1H), 7.39 (d, J = 8.4 Hz, 1H), 7.31 (t, J = 7.6 Hz, 1H), 5.90 (m, 1H), 5.15 (dd, J = 5.2, 1.2 Hz, 1H), 5.12 (d, J = 1.6, Hz 1H), 5.03 (d, J = 3.6 Hz, 2H). 13 С NMR: δ (ppm) 3-(2-Methylprop-2-en-1-yl)-2-thioxo-2,3-dihydroquinazolin-4(1H)-one (7). Yield 61%; white powder (ethanol); mp. 212-214°C. IR (KBr): (v/см À1 ) = 1655 (С═О); 1 H NMR (400 MHz, DMSO-d 6 ) δ (ppm) 12.93 (s, 1H), 7.95 (d, J = 7.2 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.37 (d, J = 8.4 Hz, 1H), 7.34 (t, J = 7.6 Hz, 1H), 4.92 (s, 2H), 4.72 (s, 1H), 4.46 (s, 1H), 1.73 (s, 3H). 13 С NMR: δ General procedure for the preparation of 7-(pmethoxyphenyl)dichlorotelluromethyl-2,3-dihydro-5H-[1,3] thiazolo[2,3-b]quinazolin-5-ones hydrochlorides. The 1 mmol of 3-alkenyl-2-thioxo-2,3-dihydroquinazolin-4(1H)-one 6 or 7, dissolved in 20 mL of acetic acid, was added to 1 mmol of p-alkoxyphenyltellutium trichloride in 20 mL of acetic acid. The reaction mixture was stirring at room temperature for 8 h. Target product was filtered and recrystallized from acetic acid. 3-[Dichloro(4-methoxyphenyl)telluromethyl]-2,3-dihydro-5H-[1,3]thiazolo[2,3-b]quinazolin-5-one hydrochloride (8). Yield55%; white powder (acetic acid); mp. 143-145°C; IR (KBr): (v/см À1 ) = 1690 (С═О); 1 H NMR (400 MHz, DMSO-d 6 ) δ (ppm) 8.07 (d, J = 8.0 Hz, 1H), 8.05 (d, J = 7.2 Hz, 2H), 7.78 (t, J = 7.6 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H), 7.46 (t, J = 8 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H), 7.08 (d, J = 7.2 Hz, 1H), 4.76 (m, 1H), 4.67 (d, J = 13.2 Hz, 1H), 4.44 (dd, J = 12.8, 7.2 Hz, 1H), April 2018Regiochemistry of Electrophilic Heterocyclization of 3-Alkenyl-2-Thioxopyrimidin-4-One by p-Alkoxyphenyltellurium Trichloride

Condensed heterocycles are well-known for their excellent biological effects and they are undeniably important compounds in organic chemistry. Electrophilic cyclization reactions are widely used for the synthesis of mono-heterocyclic compounds. This review highlights the utility of electrophilic cyclization reactions as an effective generic tool for the synthesis of various condensed heterocycles containing functional groups that are able to undergo further chemical transformations, such as nucleophilic substitution, elimination, re-cyclization, cleavage, etc. This review describes the reactions of unsaturated derivatives of different heterocycles with various electrophilic agents (halogens, arylsulfanyl chlorides, mineral acids) resulting in annulation of an additional partially saturated heterocycle. The electrophilic reaction conditions, plausible mechanisms and the use of such transformations in organic synthesis are also discussed. The review mainly focuses on research published since 2002 in order to establish the current state of the art in this area. 1 Introduction2 Electrophilic Cyclization Pathways Involving a Nitrogen Nucleo­philic Center3 Electrophilic Cyclization Pathways Involving a Chalcogen Nucleophilic Center3.1 Sulfur Centers3.2 Oxygen Centers3.3 Selenium Centers4 Strategies and Mechanisms5 Conclusion

Earlier [1] it was reported that o-aminocyanopyrazoles condense effectively with isothiocyanates to pyrazolo[3,4-d]pyrimidine-6-thiones. In the present work 5-amino-4-cyano-1-methyl-1H-pyrazole (1) was used as initial aminopyrazole.In [1] boiling ethanol was used as solvent for the condensation, and this was followed by cyclization with alkali. We used a mixture of DMF with potassium hydroxide for the condensation and cyclization of the pyrazole 1. The potassium salt of pyrazolo[3,4-d]pyrimidine-6-thione 2 was obtained as a result of the reaction without isolation of the thiourea. The thione 3 was obtained when the salt 2 was neutralized with acetic acid. N N Me CN NH 2

Electrophilic heterocyclization of 5,6-disubstituted 3-alkenyl-2-thioxothieno[2,3-

No abstract