The present invention relates to compounds of the formula Iwherein A1, A2, R1, R3, X and n are as defined in the claims, which are valuable pharmaceutically active compounds for the therapy and prophylaxis of diseases, for example of cardiovascular diseases such as hypertension, angina pectoris, cardiac insufficiency, thromboses or atherosclerosis. The compounds of the formula fare capable of modulating the body's production of cyclic guanosine monophosphate (cGMP) and are generally suitable for the therapy and prophylaxis of diseases which are associated with a disturbed cGMP balance. The invention furthermore relates to processes for preparing compounds of the formula I, to their use for the therapy and prophylaxis of the abovementioned diseases and for preparing pharmaceuticals for this purpose, and to pharmaceutical preparations which comprise compounds of the formula I.