Pyrimidines and their Benzo Derivatives

Switching the Regioselectivity of Direct C–H Arylation of 1,3‐Dimethyluracil

“…CuI dramatically lowered the yield (to 56 and 62 %, respectively), but increased the selectivity of 4a (Entries 3-5). The use of P(tBu) 3 at 130°C in the absence of CuI gave 57 % conversion to a ca.2:1 mixture of 3a/4a, while in the presence of CuI, the ratio was switched to ca. 1:6 (Entries 6 and 7).…”

“…It contains two C-H bonds capable of arylation -positions 5 and 6. Position 5 is known to be the preferred site for electrophilic substitution, [3] while C-H in position 6 is more acidic and undergoes metalation. [4] The direct C-H arylation of 1 was optimized with the reaction with p-tolyl iodide (2a) by using Pd(OAc) 2 in combination with diverse ligands and with varying amounts of CuI in the presence of Cs 2 CO 3 (Scheme 1, Table 1).…”

“…In addition, arylation in position 5 is often used for labeling of nucleotides, oligonucleotides, and DNA for applications in bioanalysis or chemical biology. [2] The 5-or 6-aryluracils can be prepared by heterocyclization [3] or by cross-coupling reactions [4] of halouracils with arylboronic acids or -stannanes or of metalated uracils with aryl halides. However, some aryluracils are still difficult to prepare and, therefore, development of alternative methodologies is of interest.…”

Synthesis and Structural Study of Some Pyrimidinium Hexafluoridosilicates

“…32 Chloro substituent on position 2 of pyrimidine ring is highly prone to water substitution reaction in acidic HF medium where the first step probably is the protonation of one heterocyclic nitrogen atom. This Table 3.…”

4-Chloro-6-ethoxy-2-(methylthio)pyrimidine

“…The presence of pyrimidines has been reported for over a century and their chemistry has been reviewed [1]. Pyrimidines also find a plethora of uses as pharmaceuticals, as antiinflammatory [2], anti-microbial [3], anti-HIV [4], anti-malarial [5] and anti-tumour [6] agents.…”