using System;

using System.Linq;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            {

              ""innerObj1"": {

                ""1. Information"": ""unimportant""

              },

              ""innerObj2"": {

                ""2017-09-19 16:00:00"": {

                  ""number1"": ""75.4500""

                },

                ""2017-09-19 15:55:00"": {

                  ""number2"": ""75.4200""

                }

              }

            }";

        JObject obj = JObject.Parse(json);

        string[] numbers = ((JObject)obj["innerObj2"]).Properties()

            .SelectMany(jp => ((JObject)jp.Value).Properties())

            .Select(jp => (string)jp.Value)

            .ToArray();

        Console.WriteLine(string.Join(", ", numbers));

    }

}