The process in which relatively unspecialized cells of the ectoplacental cone acquire specialized structural and/or functional features that characterize chorionic trophoblasts. These cells will migrate towards the spongiotrophoblast layer and give rise to syncytiotrophoblasts of the labyrinthine layer. [ http://purl.obolibrary.org/obo/CL_0011101 http://www.ncbi.nlm.nih.gov/pubmed/16983341 GOC:dph ]