IF the stock purchase meets the requirements as discussed here, and in IRS Notice 88-37, the interest does go to Sch E page 2:

https://www.hhcpa.com/blogs/income-tax-accountants-cpa/interest-expense-related-to-acquisition-of-a-...

In Lacerte, it's entered as an "un-reimbursed" expense, and generates a diagnostic that 'generally' an S-Corp shareholder doesn't get to deduct un-reimbursed expenses anywhere other than Sch A.

Interest on acquisition is handled a bit differently.