doRefreshToken(refreshToken: string): Observable<any> {
  const body = new HttpParams()
    .set('grant_type', "refresh_token")
    .set('refresh_token', refreshToken);

  return this.http.post('/login',
    body.toString(),
    {
      headers: new HttpHeaders()
        .set('Content-Type', 'application/x-www-form-urlencoded')
    }
  );
}

 $.ajax({
          url: "/login", // web.config --> appConfiguration -> tokenPath
          data: {
                   grant_type: "refresh_token",
                   refresh_token: refreshToken
                },
                type: 'POST', // POST `form encoded` data
                contentType: 'application/x-www-form-urlencoded'
            })

doRefreshToken(refreshToken: string): Observable<any> {
  const body = new HttpParams()
    .set('grant_type', "refresh_token")
    .set('refresh_token', refreshToken);

  return this.http.post('/login',
    body.toString(),
    {
      headers: new HttpHeaders()
        .set('Content-Type', 'application/x-www-form-urlencoded')
    }
  );
}