Granada to Antequera

I just plugged Granada to Antequera into Alsa's website and got departures at 03:00, 07:00, 11:45, and 18:18. The 7:00 would be too tight a connection as it arrives at 8:50 presuming it's dead on time.

What's your travel date?

Normally one would just buy a ticket from Granada to Barcelona, and Renfe would tell you what connecting trains to use. For weekdays I see a 6:45 AM departure from Granada that arrives at Antequera at 8:13 AM, with the AVE to Barcelona departing at 9:02 AM. I believe the first leg is by bus because of on-going work on the rail line. I wouldn't worry about that connection.

However, if you haven't already bought the train tickets from Antequera, I recommend looking at the possibility of flying. Vueling has non-stops from Granada to Barcelona. I don't know which days of the week they fly, but I see a 9:20 AM departure for March 13.

I agree with Acraven, there’s no need to buy separate tickets for your journey from Granada to Barcelona.

If you don’t want to depart Granada at 6:45am, there’s another option departing at 12:45 and arriving in Barcelona at 20:22.

Due to the ongoing railroad work around Granada, the journey entails traveling by bus ( provided by Renfe) from Granada’s train station to Antequera where you’ll be guided to the train and continue the rest of your journey to Barcelona.

What’s your overall itinerary?
Perhaps there’s a way you can change your itinerary to avoid this long trek.
You may consider traveling to Sevilla after Granada; then after your visit there, you can travel to Madrid then to Barcelona.

Enjoy your time in Spain!

As acraven suggests, flying is probably better (that's what most people do) because the overland journey is 7 hours or more.