init.el

(defun tangle-init ()
  "If the current buffer is 'init.org' the code-blocks are
   tangled, and the tangled file is compiled."
  (when (equal (buffer-file-name)
               (expand-file-name (concat user-emacs-directory "init.org")))
    ;; Avoid running hooks when tangling.
    (let ((prog-mode-hook nil))
      (org-babel-tangle)
      (byte-compile-file (concat user-emacs-directory "init.el")))))

(add-hook 'after-save-hook 'tangle-init)