I am paying back a 401K loan can I deduct this?

No.  The loan payments are a payback into the tax deferred retirement account.  They are not deductible.  The loan from the 401(k) is not reported on a federal tax return.

A simple way to look at this is that you did not have to pay taxes on the money when you received the loan, so you do not get a deduction when you put is back.  The interest payments that you make on this loan are also not deductible since the loan is considered a personal loan.