After successfully deploying and configuring vCAC (6.0.1) appliance and Identity Server in my lab, I started installing the IAAS server. Reading the prerequisite that currently only Windows Server 2008 R2 and Windows Server 2012 are supported, no Windows Server 2012 R2, I started installing a copy of Windows Server 2012. Before installing anything on the freshly deployed server I run Windows Update. What else would you do?
Then I run successfully the VMware re-req automation script and confidently started the IAAS setup and hit an error right away:

(Microsoft .NET Framework 4.5 Full package must be installed on a supported operating system for installation to continue. See the vCloud Automation Center Support Matrix for a list of supported operating systems)

Ok, I opened the vCloud Automation Center Support Matrix and the only relevant parts are the requirement for Windows Server 2012 and IIS 2012. Next I double checked that .Net Framework 4.5 is installed.

After frustratingly searching around I finally found a hint in a blog post, explaining that Windows Server 2012 R2 is not working because of .NET 4.5.1.

Knowing the problem it was easy to search for it and I found following statement in the release notes:

• Requirement for .NET 4.5 does not extend to .NET 4.5.1
  .NET 4.5.1 is not currently supported. While system requirements state that .NET 4.5 is required, they should also explicitly state that vCloud Automation Center release 6.0 and 6.0.1 do not support .NET 4.5.1.

The last part was to figure out which update I had to uninstall to get rid of .NET 4.5.1. Again after searching I finally found the update which has to be uninstalled KB2881468 and successfully started the vCAC IAAS Server setup after uninstall!

To temporarily block the installation of the .NET Framework 4.5.1, have a look at KB2721187.