There are described compounds of formula I, ##STR1## in which R.sub.1 represents benzofurazanyl, pyridyl or phenyl, the pyridyl or phenyl being substituted by one or more of the groups halogen, nitro, --CN, --OR.sub.9, --S(O).sub.p R.sub.9, or alkyl C1 to 6 optionally substituted by halogen,p is 0, 1 or 2,R.sub.2 and R.sub.3, which may be the same or different, each represent hydrogen; alkyl C1 to 6 optionally substituted by one or more of the groups halogen, cyano, --XR.sub.4, --NR.sub.5 R.sub.6 or phenyl; cycloalkyl C3 to 8 optionally substituted by alkyl C1 to 6; a 4, 5 or 6 membered oxygen or nitrogen containing heterocyclic ring which is optionally substituted by alkyl C1 to 6 the alkyl in turn optionally being substituted by one or more phenyl groups;R.sub.5 and R.sub.6, which may be the same or different, each represent alkyl C1 to 6 optionally substituted by phenyl,Y and Z together form a bond, and additionally, when R.sub.8 is an electron withdrawing group Y may be hydrogen and Z may be hydroxy,one of R.sub.7 and R.sub.8 represents alkyl C1 to 6 and the other represents phenyl,or R.sub.7 and R.sub.8 may be the same or different and each represents phenyl optionally substituted by one or more of alkyl C1 to 6, halogen, alkoxy C1 to 6 or nitro; amino; alkyl C1 to 6 substituted by halogen; --CN; --CH.sub.2 OH; --CHO or --CH(OR.sub.9).sub.2,X is O or S,R.sub.4 is alkyl C1 to 6 or phenyl,R.sub.9 is alkyl C1 to 6, with certain provisons.There are also described processes for making the compounds, and their formulation and use as pharmaceuticals for treatment of hypertension, angina, or congestive heart failure.