I wouldn't 301 anything from example1 & 2 to example.com. It's such an obviously spammy setup that you want to completely disengage example.com from that strategy and those sites.
I'd have to give it some more thought about whether I'd go with levo's or Planet13's approach for removal... it should be either total removal, or 410s, IMO... or eventually both.
Just thinking out loud... perhaps having Google see all outbound link pages removed from example1 and example2 before you take those sites down lets Google see a sequence of operations that suggests conscious removal. It's hard to say what they'd make of the A records vanishing or how fast the removal needs to be. Check dates on links and spidering dates if its easy.
Look at other inbounds to the main site as well. Obviously you want to get rid of the outbound links to the two other sites... and maybe check to see whether there might be some link circles involving yet other sites that comes back around.
Check also where all of these sites are hosted. If all on related IPs, that makes the relationships unmistakable.
You've also got a big content rebuilding project to deal with.