In view of the low reactivity of the chlorine in 7-methyladenines, these compounds were converted into their salts (II, III). The formation of positively-charged carbonium ions on protonation enhances the electrophilicity of the molecule, and facilitates replacement of the chlorine by sulfur. In addition to 2-thioadenine (IV), condensation of the salt (II) with thiourea gave some of the sulfide (V). 2-Amino-6-chloro-7-methylpurine (IX) gave 6-thio-7- ...
