The minimum requirements for Captain for any Transport Category aircraft is an ATPL, as OhNoCB pointed out. So, the absolute minimum will be whatever the minimum amount of hours is required to hold an ATPL - normally 1,500 total time plus a whack of other minor time building exercises such as night, IFR, etc.
As he correctly pointed out, however, it will be up to YOUR company to decide what THEIR minimum requirements for upgrades are. You'll find it in your Company Ops Manual under Pilot Requirements - or whatever it's titled there. There could also be seniority, insurance, and a whole host of other company specific requirements that, frankly, only your HR or Flight Ops department can answer for you.
That's the reason you can't find it in the regs.