SharePoint 2013 SP1 is supported on .NET framework 4.6 but there is a known issue when installing SharePoint 2013 on top of .NET framework 4.6
During the installation the installer verifies if .NET framework 4.5 is available and fails to install SharePoint 2013 if .NET framework 4.6 is installed.
The reason is that .NET framework 4.6 replaces .NET framework 4.5 and is not a side-by-side installation. As the installer is not able to match .NET framework 4.6 to .NET framework 4.5 it will prevent the installation.
The solution for this issue is to postpone the installation of .NET framework 4.6 till after SharePoint 2013 SP1 has been installed.
More details in the following KB article:
- KB 3087184 - SharePoint 2013 Setup error occurs if the Microsoft .NET Framework 4.6 is installed
[Update September 14th, 2016]: This is now fixed. See the following blog post for details: https://blogs.technet.microsoft.com/stefan_gossner/2016/09/14/sharepoint-2013-installer-now-supports-net-framework-4-6-and-above/