This invention provides compounds of Formula I, methods for their preparation and use for preparing compounds of Formula II ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.5, R.sup.6, X and n are as defined in the disclosure. This invention also discloses preparation of compounds of Formula III ##STR00002## wherein R.sup.1, R.sup.2, R.sup.7, R.sup.8, R.sup.9 and n are as defined in the disclosure. This invention also pertains to certain compounds of Formula 4 and 6 used to prepare compounds of Formula I. ##STR00003## wherein R.sup.1, R.sup.2, R.sup.5, X and n are as defined in the disclosure.