The present invention relates to novel 3 4 dihydro pyrrolo[l 2 a]pyrazin 1 ylamine derivatives as inhibitors of beta secretase also known as beta site amyloid cleaving enzyme BACE BACE1 Asp2 or memapsin2. The invention is also directed to pharmaceutical compositions comprising such compounds to processes for preparing such compounds and compositions and to the use of such compounds and compositions for the prevention and treatment of disorders in which beta secretase is involved such as Alzheimer s disease (AD) mild cognitive impairment senility dementia dementia with Lewy bodies Down s syndrome dementia associated with stroke dementia associated with Parkinson s disease or dementia associated with beta amyloid.