How to serialize a Json object? Delphi XE7

I need to generate an Object that represents a JSON file and Delphi is generating me the following

ERROR: 'Internal: Invalid pair name {"directory": "d: \ Folder \ Doc"}: expected type or ref'

In the line of code:

  objetoJson := UnMar.UnMarshal(oJson) as TJson;

Could anyone tell me what the problem is and how to solve it, please?

program Project2;

{$APPTYPE CONSOLE}

{$R *.res}

uses   System.SysUtils, Data.DBXJSONReflect, JSON;

type
  TJson = CLass
    diretorio: string;
  end;

var
  oJson: TJSONObject;
  objetoJson: TJson;
  UnMar: TJSONUnMarshal;
begin
  try
// Crio o Json
oJson := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes('{"diretorio": "d:\Pasta\Doc"}'),0) as TJSONObject;
// Mostra o conteudo no Json no console
Writeln('Conteudo do objeto Json: '+ojson.ToString);
UnMar := TJSONUnMarshal.Create;
try
  // Tento repassar o Objeto de Json para a Classe
  objetoJson := UnMar.UnMarshal(oJson) as TJson;
  try
    writeln(  objetoJson.diretorio);

  finally
    objetoJson.Free;
  end;
finally
  UnMar.Free;
end;
  except
on E: Exception do
begin
  Writeln('Erro ao tentar usar UmMarshal: ');
  Writeln( E.Message);
end;
  end;
  readln;
end.