Hydroxyalkyl-xanthines from alkenyl-xanthines - by acid catalysed addn. of water

Hydroxyalkyl-xanthines of formula (I): (where at least one of R1, R2 and R3 is a 4-8C (omega-1)-hydroxyalkyl gp. with no branching in the (omega-1)-posn., and the others are 1-12C alkyl, or R1 and/or R2 can also be H) are prepd. by Markownikoff addition of H2O to the corresp. (omega-1)-alkenyl-xanthines (II) in the presence of a catalyst. (I) are useful as medicaments, e.g. 1-(5-hydroxyhexyl)-3, 7-dimethylxanthine (Ia) has circulatory activity. The process gives almost quantitative yields without the use of unstable reagents (cf. the metal hydride redn. of the corresp. keto cpds.). The reaction is pref. effected at 40-150 degrees C (esp. 60-120 degrees C) in an aq. soln. or suspension contg. an acid catalyst, e.g. H2SO4, HCl, HNO3, H3PO4, CF3SO3H or an SO3H-contg. ion exchanger (H form). Cpds. (II) can be prepd. by reacting an haloalkene with an alkali metal salt of theobromine (or an analogue thereof).