TY - JOUR
T1 - N,N-Dialkyl-N′-Chlorosulfonyl chloroformamidines in heterocyclic synthesis. Part XI.∗Some substitution reactions of pyrazolo[1,5-b][1,2,4,6]thiatriazine 1,1-Dioxides
AU - Norman, Rebecca
AU - Perkins, Michael
AU - Liepa, Andris
AU - Francis, Craig
PY - 2015/2/24
Y1 - 2015/2/24
N2 - The recently discovered pyrazolo[1,5-b][1,2,4,6]thiatriazine template was shown to possess four nucleophilic sites (N2, N4, C5, N7) that underwent a range of substitution reactions. Methylation occurred at both N4 and N7. Alkylation with benzylic halides occurred preferentially at N7, regardless of the solvent, but also occurred at C5, N4, and N2. Similar alkylation with -halo esters occurred at both N4 and N7, but the latter derivatives underwent a novel pyrazole ring expansion to afford pyrimido[1,6-b][1,2,4,6]thiatriazine derivatives. Bromination of pyrazolo[1,5-b][1,2,4,6]thiatriazines afforded unstable 5-bromo derivatives. Tosylation occurred selectively at C5, but in modest yield; catalysis with 1-methylimidazole also led to a low yield of the 5,5′-dimer. The action of HCl on N7-benzylated pyrazolo[1,5-b][1,2,4,6]thiatriazines readily caused extrusion of sulfur dioxide to produce pyrazolo-guanidines.
AB - The recently discovered pyrazolo[1,5-b][1,2,4,6]thiatriazine template was shown to possess four nucleophilic sites (N2, N4, C5, N7) that underwent a range of substitution reactions. Methylation occurred at both N4 and N7. Alkylation with benzylic halides occurred preferentially at N7, regardless of the solvent, but also occurred at C5, N4, and N2. Similar alkylation with -halo esters occurred at both N4 and N7, but the latter derivatives underwent a novel pyrazole ring expansion to afford pyrimido[1,6-b][1,2,4,6]thiatriazine derivatives. Bromination of pyrazolo[1,5-b][1,2,4,6]thiatriazines afforded unstable 5-bromo derivatives. Tosylation occurred selectively at C5, but in modest yield; catalysis with 1-methylimidazole also led to a low yield of the 5,5′-dimer. The action of HCl on N7-benzylated pyrazolo[1,5-b][1,2,4,6]thiatriazines readily caused extrusion of sulfur dioxide to produce pyrazolo-guanidines.
UR - http://www.scopus.com/inward/record.url?scp=84941061996&partnerID=8YFLogxK
U2 - 10.1071/CH14547
DO - 10.1071/CH14547
M3 - Article
SN - 0004-9425
VL - 68
SP - 1011
EP - 1024
JO - Australian Journal of Chemistry
JF - Australian Journal of Chemistry
IS - 7
ER -