AlwaysOn with single node possible?

I am currently reviewing a SQL2012 migration plan which is a migration from a traditional 2-node 2008R2 cluster to a 2012 2-node AlwaysOn solution. The idea is to dismantle the cluster and convert the 2nd server to SQL2012 including AlwaysOn. After the databases are migrated, the first server is also converted and added to the AlwaysOn group. But is this method possible? AFAIK you can't create a single node AlwaysOn cluster.