.alpha.,.alpha. dialkylbenzyl derivatives

An .alpha.,.alpha.-dialkylbenzyl derivative of the formula I

• wherein
• Ar.sup.1 is phenyl or naphthyl, and Ar.sup.1 may optionally bear up to four substituents selected from halogeno, hydroxy, cyano, (1-4C)alkyl, (1-4C)alkoxy, fluoro-(1-4C)alkyl, phenyl, benzoyl, phenyl-(1-4C)alkyl, .alpha.,.alpha.-difluorobenzyl, .alpha.-hydroxybenzyl and .alpha.-[(1-4C)alkoxy]benzyl and wherein said phenyl substituent or any of said substituents which contain a phenyl group may optionally bear a substituent selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy;
• A.sup.1 is a direct link to X.sup.1 or is (1-3C)alkylene;
• X.sup.1 is oxy, thio, sulphinyl or sulphonyl;
• the phenylene group [which carries the groups X.sup.1, (R.sup.3) and C(R.sup.1)(R.sup.2)(Q)] may optionally bear one or two substituents R.sup.3 selected from halogeno, hydroxy, amino, nitro, cyano, carbamoyl, ureido, (1-4C)alkyl, (1-4C)alkoxy and fluoro-(1-4C)alkyl;
• each of R.sup.1 and R.sup.2, which may be the same or different, is (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, fluoro-(1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl and wherein said phenyl or phenyl-(1-4C)alkyl group may optionally bear one or two substituents selected from halogeno, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy, provided that both of R.sup.1 and R.sup.2 are not methyl or fluoromethyl;
• and
• Q is cyano, amino, nitro, formyl, (1-4C)alkoxy, thiazolyl or (2-4C)alkanoyl;
• or a pharmaceutically-acceptable salt thereof.