3-Ethynylimidazo[1,2-B]pyridazine943320-61-4100 % similar 3-Bromoimidazo[1,2-B]pyridazine18087-73-550 % similar 3-Ethynylpyridine2510-23-837 % similar 2-Ethynylpyridine1945-84-234 % similar