Typically, Marriott Hotels will not allow room booking directly with individual hotels as they require calling the reservation number - From Europe - 00-800-3994-2290, U.S & Canada - 1-800-399-4229. If you have trouble reaching reservation desk with either of these, try 44-0-20-7012-7312
However, if you'd like to try calling the respective Marriott hotels in Chicago O'Hare area; Courtyard and R.I. are close to the Marriott O'Hare Hotel:
Marriott Hotel O'Hare - 844-707-0124
Marriott Courtyard - 855-809-3511
Marriott Residence Inn - 847-707-0124
Marriott hotels usually don't post email addresses until you receive a room confirmation.