The present invention relates to compounds of formula I: or pharmaceutically acceptable acid addition salts thereof, where; R1 is C1-C6 alkyl, substituted C1-C6 alkyl, C3-C7 cycloalkyl, substituted C3-C7 cycloalkyl, C3-C7 cycloalkyl-C1-C3 alkyl, substituted C3-C7 cycloalkyl-C1-C3 alkyl, phenyl, substituted phenyl, heterocycle, or substituted heterocycle; R2 is hydrogen, C1-C3 alkyl, C3-C6 cycloalkyl-C1-C3 alkyl, or a group of formula II R3 is hydrogen or C1-C3 alkyl; R4 is hydrogen, halo, or C1-C3 alkyl; R5 is hydrogen or C1-C3 alkyl; R6 is hydrogen or C1-C6 alkyl; and n is an integer from 1 to 6 inclusively. The compounds of the present invention are useful for activating 5-HTlF receptors, inhibiting neuronal protein extravasation, and for the treatment or prevention of migraine in a mammal. The present invention also relates to a process for the synthesis of intermediates in the synthesis of compounds of Formula I.