REACTIONS WITH 6-METHYL-2-THIOURACIL SYNTHESIS OF DIPYRIMIDINO[2,1-b:1′,2′-c]THIAZINE. A NEW RING SYSTEM

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

A series of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines was synthesized for the first time by the reactions of chloroethynylphosphonates with unsubstituted and 5(6)-substituted 2-thiouracils. The reaction of chloroethynylphosphonates with 6-substituted 2-thiouracils bearing electron-donor groups (CH₃, Ph) proceeded with high regioselectivity involving the cyclization through the N³-nitrogen atom to form new 3-phosphonylated thiazolo[3,2-a]-5-oxopyrimidines with good yield. In the case of unsubstituted and 5-methyl-2-thiouracils, cyclization occurred predominantly through the N¹ atom and partially via the N³-nitrogen atom to form a mixture of the corresponding thiazolo[3,2-a]-7- and 5-oxopyrimidines. A dramatic change in the reaction regioselectivity was observed in the case of 6-trifluoromethyl-2-thiouracil that afforded 2- and 3-phosphonylated 5-oxothiazolopyrimidines in a 1:1 ratio.

Regioselective convergent synthesis of 2-arylidene thiazolo[3,2-a]pyrimidines as potential anti-chikungunya agents

Convergent and convenient regioselective synthesis of novel thiazolo[2,3-a]pyrimidine derivatives was accomplished using the one-pot reaction of 6-ethylthiouracil, bromoacetic acid, anhydrous sodium acetate, acetic anhydride, acetic acid and suitable aldehyde. X-ray crystallographic study reveals the presence of the Z configuration of only one regioisomer confirmed by computational studies as being the most likely isomer present.

Convergent and convenient regioselective synthesis of novel thiazolo[2,3-a]pyrimidines was accomplished using the one-pot reaction of 6-ethylthiouracil, bromoacetic acid, anhydrous sodium acetate, acetic anhydride, acetic acid and suitable aldehyde.

Synthesis and biological evaluation of novel pyrimidines derived from 6-aryl-5-cyano-2-thiouracil

Starting from 6-aryl-5-cyano-2-thiouracil derivative 1a-f, a series of novel thiazolo[3,2-a]pyrimidines 4a-f were synthesized. The mechanism and the regioselectivity of the studied reactions are discussed. In addition, a series of tetrahydro-4-H-pyrimido[2,1-b][1,3]thiazines 7a-e and 2-((ethoxymethyl)thio)-4-aryl-1,6-dihydropyrimidines 9b,c,e were synthesized. The anti-microbial activities of some of the prepared compounds were screened, and the results revealed that compounds 3c and 4c were more active than the standard (Ampicillin) against gram positive bacteria (Pseudomonas aeruginosa). Moreover, compounds 4b,e and 3f were found to be good antifungal agents against the studied fungal strains.

Electrolytic partial fluorination of organic compounds. 42.(1) marked solvent effects on regioselective anodic monofluorination of 4-oxo-2-pyrimidyl sulfides

Regioselective anodic monofluorination of 4-oxo-2-pyrimidyl sulfides was investigated under various electrolytic conditions. Anodic fluorination was successfully carried out using Et(4)NF.4HF in dimethoxyethane (DME) to provide the corresponding alpha-fluorinated products in good yields. In contrast, acetonitrile (MeCN) was not suitable for the anodic fluorination due to the severe anode passivation during the electrolysis. A mixed solvent of DME and MeCN was found to be also effective for the fluorination, and the product yield increased with an increase of the ratio of DME to MeCN. The superiority of DME can be explained mainly in terms of the suppression of the anode passivation and enhancement of the nucleophilicity of the fluoride ions. Such marked solvent effects on the anodic fluorination were discussed in detail.