Synthesis of 8-substituted xanthines via 5,6-diaminouracils: an efficient route to A2A adenosine receptor antagonists

A one-pot route to 8-substituted xanthines has been developed from 5,6-diaminouracils and carboxaldehydes. The process, promoted by (bromodimethyl)sulfonium bromide, is mild and efficient and eliminates the need for external oxidants. Yields are good and the process is applicable to a range of substrates including a family of A2A adenosine receptor antagonists. Preparation of a new analog of the antagonist KW-6002 is presented, and in situ bromination of aryl substituted products demonstrated.