Retrieve data from Dynamics Customer Engagement Web API using .Net 4.5.2

We need to retrieve data from Dynamics Customer Engagement from an application developed in c# .Net framework 4.5.2. We know that for v9.0 of dynamics web API .Net framework 4.6.2 or higher is needed. What we need to know is if there is any way to query data from dynamics Customer Engagement using our applications requirements (maybe using another API version) because we can't change our .Net version for other reasons. We also appreciate help finding some documentation for that.

We try to use an HttpClient to make the API calls. The problem is in the authentication step using Microsoft.IdentityModel.Clients.ActiveDirectory.