Novel tricyclic dihydropyrazines as potassium channel openers

The invention is directed to a compound of formula I:

• R1 is selected from the group consisting of hydrogen, halogen, carboxy, C1-4 alkyl, halogenated C1-4alkyl, —C(O)—C1-4 alkyl, —C(O)-(halogenated C1-4alkyl), —C(O)O—C1-4alkyl, —S(O)0-2—C1-4alkyl, cyano and nitro;
• R2 is selected from the group consisting of hydrogen, halogen, carboxy, C1-4 alkyl, halogenated C1-4alkyl, —C(O)—C1-4 alkyl, —C(O)-(halogenated C1-4alkyl), —C(O)O—C1-4alkyl, —S(O)0-2—C1-4alkyl, cyano and nitro;
• n is 1 to 2.
• R3 is hydrogen or C1-4alkyl;
• or a pharmaceutically acceptable salt thereof.