ASP.Net Error: Microsoft SharePoint is not supported with version 4.0.30319.42000 of the Microsoft .Net Runtime

I created a Web API using .NET 4.5 and referencing .NET 3.5 library that uses the Sharepoint 2010 libraries.

I am getting a below mentioned error :

"Microsoft SharePoint is not supported with version 4.0.30319.42000 of the Microsoft .Net Runtime."

I know that SharePoint is compatable with CLR2.0.

Is there any why, I can make my WebAPI to communicate with Sharepoint 2010.