Imidazole derivatives. VII. Reaction of 1- acylimidazoles with dialkyl acetylenedicarboxylates: synthesis of imidazo [1,2-a]pyridines, 2-imidazolylmaleates, 1,5-dihydroimidazo[1,2-a]pyridines, furo [2',3':2,3]pyrrolo[1,2-a]imidazoles ..