As indicated in the about page of ReDJ component, you can find the full MySQL regexp documentation here:
dev.mysql.com/doc/refman/5.1/en/regexp.html
Anyway, here's the correct entries for your redirect:
1)
www.sitename.com/products/ redirect to
www.sitename.com/products.html
From URL: ^/products/$
To URL: http://{siteurl}/products.html
2)
www.sitename.com/products/email redirect to
www.sitename.com/email.html
From URL: ^/products/email$
To URL: http://{siteurl}/email.html
3)
www.sitename.com/products/virus-scan/ redirect to
www.sitename.com/services/virus-scan.html
From URL: ^/products/virus-scan/$
To URL: http://{siteurl}/services/virus-scan.html
The caret ^ means "start with", while the dollar $ means "end with". These are useful for restrict matches as in your cases.
Regards,
Luigi