No, its not - turf needs to root into loose friable soil beneath, so you'd need to strip off the turf you've got first, even if the top is dead and brown looking - there'll be a mat of roots beneath the dead part. And trying to cut out areas of lawn, then insert new turf is no easy task - it invariably ends up too high or too low in comparison to the surrounding, older turf. If its 75% of the lawn and you can't bear to wait to see whether it recovers eventually, strip it all off and buy completely new turf and returf the whole area, in other words, take up the existing lawn and lay another one.

You'll also want to fix whatever problem caused it to turn brown in the first place.

Pull it up in places and check for grubs.

Guys, this question is related to the one about overdosing with fertilizer... the cause is incontrovertable - human error!

Sorry, Bamboo and Katharine, I answered this question first, and then got distracted before correcting myself to reflect the first question. Gnarly_gnome's answer should work, but you can hurry it up a little by watering the lawn deeply--assuming the drainage is good. Possible consequences to water table or surrounding streams, though.