Iphone 5 connection to wifi which requires vpn as default

I am trying to connect to a corporate guest wifi system that requires all connnections to go through a vpn. I can associate the iphone with the access point but I am immediatly presented with an authentication request for www.apple.com. As I have no such credentials I have to press cancel which then drops the wifi connection. ~I had no such problems on an iphone 4 running previous verison of ios, is this an issue with the new os for iphone 5 and is there a work around?