Cyclofunctionalization of 6-alkenylsulfanylpyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]-pyrimidin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones with arenesulfenyl chlorides

Reactions of 6-allylsulfanylpyrazolo3,4-d]pyrimidin-4(5H)-one with arenesulfenyl chlorides in chloroform gave products of addition of the latter at the exocyclic double bond, while analogous reactions in acetic acid in the presence of LiClO₄ were accompanied by intramolecular electrophilic cyclization involving the N⁷ atom. 6-Cinnamylsulfanylpyrazolo3,4-d]pyrimidin-4(5H)-one reacted with arenesulfenyl chlorides in acetic acid in the absence of electrolyte to produce fused pyrazolo4′,3′: 5,6]pyrimido2,1-b]1,3]thiazine derivatives. Introduction of a bulky phenyl group into position 1 of the pyrazolo3,4-d]pyrimidine system reduces the yield of the corresponding intramolecular cyclization product at N⁷ as a result of concurrent formation of acyclic addition product. DOI