The only means Michael Cohen knew to contact Russian leadership was via the 'Contact Us' link on their very public web page.  He had no direct line or back channel to Putin or to anyone connected to Putin or even anyone of significance in the Russian business community that he could reach out to directly about his efforts to explore a Trump Tower project in Russia.  He pursued this project up until at least June, 2016 with no back channel connection to anyone of significance in Russia.