2 2 6 6-tetramethylpiperidine lithium July 8, 2019 16 32 64 128 2 2 6 6-tetramethyl-piperidine 2 2 6 6-tetramethyl-4-piperidone 2 2 6 6-tetramethylpiperidine solubility 2 2 6 6-tetramethylpiperide