Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother, thank you for your question and your interest to be knowledgeable about Islam and its rituals.
As for your question, there is no evidence in the Shari`ah stating having a beard as a condition of leading Prayers. So, a beardless man may lead people in Prayer if he is qualified to. However, an imam should be a role model in all matters, including following the Sunnah.
Responding to your question, Sheikh Kifah Mustapha, the Imam and Associate Director at the Mosque Foundation, one of the largest Islamic Centers in Chicago, states:
I have not passed on any text from the Prophet (peace and blessings be upon him) that makes the beard as a condition for the validation of prayer of an individual or imam.
But, being an imam means being a role model in all that of the Sunnah of the Prophet (peace and blessings be upon him). So, regardless of the dispute between scholars about growing beards as being obligation or just a sunnah, an Imam should always try to perfect all matters of the Sunnah as I mentioned for being in the role model position.
Allah Almighty knows best.