Purchased points don't count toward companion pass.
If your travel is complete in 2019 that will count as 2019 companion pass points. If, for example, you have a round trip spanning year-end, you could phone and ask for the reservation to be split into two halves to force the outbound half to post for 2019. But would that give you 6000 points for the one-way? Not unless it was a $500 Business Select fare.
Earning 6000 companion points in two days is a tall order. Maybe there is a hotel bonus out there. Simplest is a $500 round trip (points run) today in Business Select or a $600 trip in at Anytime fare.
Do I actually need to take the flight in order to get the points? I ask because I'm still on a trip right now.