The negotiations are destined to fail because of the way they have been set up and the preconditions of the United States and its allies in the Syrian opposition demanding that President Bashar al-Assad agree to leave government before negotiations go forward.
The setup for failure begins with the limited participation. The rigged nature of the negotiations was demonstrated when the UN had to rescind an invitation to Iran to participate at the demand of the United States and the Syrian opposition group. Iran is a close ally of Syria and keeping them out of the negotiations is an effort to weaken and isolate Syria. It is an indication of a desire by the United States for a preordained conclusion rather than a fair negotiation between the parties.