I was wondering if the following example would be considered to be substantially similar securites under the wash sale rule.

On Dec 1 Company A announces that they have reached an agreement with Company B to acquire company B for 0.5 shares of A for each share of B, subject to shareholder and regulatory approval.

I have owned A for some time but bought it at 100/share and it is now at 60/share. However, B is at only 20/share when the deal is announced and is quickly rising. I sell A at a 40/share loss and put all the money into B the same day.

Is this to be considered a wash sale, even though it is two different companies, and the deal is still subject to approval and will be months before it is final?