It is not advisable to contact the examiner - From the MPEP - 1134 Third Party Inquiries and Correspondence in a Published Application
The Office considers inappropriate any third-party inquiry, or submission in an application that is not provided for in 37 CFR 1.290 or 37 CFR 1.291. Any submission filed by a third party in an application that does not comply with the requirements of 37 CFR 1.290 or 37 CFR 1.291 will not be entered into the application file and will be discarded.
Office personnel (including the Patent Examining Corps) are instructed
to: (1) not reply to or act upon any third-party inquiry or other
submission in an application, except those in compliance with 37 CFR
1.290 or 37 CFR 1.291; and (2) decline to accept oral or telephone comments or submissions about applications from third parties. When
refusing third-party telephone or oral discussions, examiners may call
the party’s attention to the statutory prohibition on initiating
protests, or 37 CFR 1.2 (all Office business should be transacted in
writing), as appropriate. See Third Party Attempts to Protest or
Otherwise Oppose the Grant of a Published Application, 1269 Off. Gaz.
Pat. Office 179 (April 22, 2003). The Office may also refer
third-party inquiries, or submissions not provided for in 37 CFR 1.290
or 37 CFR 1.291, by registered practitioners in applications to the
Office of Enrollment and Discipline for appropriate action.
One thing that you might consider is to send a copy of the art to the inventor or to the inventor's agent or attorney. IF they happen to read it and think it is relevant they will be bound to inform the examiner via an IDS form. If you were a registered patent practitioner, this would be of debatable ethics.
If there is a corresponding PCT or foreign application you may be able to file a third-party observation on that application with that entity. This will cause the document to be brought to the attention of the applicant who should then file it on a IDS to the USPTO.