The present invention relates to compounds of formula I: (I) or a pharmaceutically acceptable acid addition salt thereof, where; X is C(R.sup.3c.dbd. or N.dbd.; R.sup.1 is C.sub.2 C.sub.6 alkyl, substituted C.sub.2 C.sub.6 alkyl, C.sub.3 C.sub.7 cycloalkyl, substituted C.sub.3 C.sub.7 cycloalkyl, phenyl, substituted phenyl, heterocycle, or substituted heterocycle; R.sup.2 is hydrogen, C.sub.1 C.sub.3 n-alkyl, C.sub.3 C.sub.6 cycloalkyl-C.sub.1 C.sub.3 alkyl, or a group of formula II (II) provided that when R.sup.1 is C.sub.2 C.sub.6 alkyl or substituted C.sub.2 C.sub.6 alkyl, R.sup.2 is hydrogen or methyl; R.sup.3a, R.sub.3b, and, when X is C(R.sup.3c).dbd., R.sup.3c, are each independently hydrogen, fluoro, or methyl, provided that no more than one of R.sup.3a, R.sup.3b, and R.sup.3c may be other than hydrogen; R.sup.4 is hydrogen or C.sub.1 C.sub.3 alkyl; R.sup.5 is hydrogen, C.sub.1 C.sub.3 alkyl, or C.sub.3 C.sub.6 cycloalkylcarbonyl, provided that when R.sup.3a is other than hydrogen, R.sup.5 is hydrogen; R.sup.6 is hydrogen or C.sub.1 C.sub.6 alkyl; and n is an integer from 1 to 6 inclusively. The compounds of the present invention are useful for activating 5-HT.sub.1F receptors, inhibiting neuronal protein extravasation, and for the treatment or prevention of migraine in a mammal. ##STR00001##