“…Due to the pharmaceutical importance, and to overcome the synthetic constraints reported by Pfizer Inc., the synthesis of tofacitinib was extensively studied and several procedures were published [ 119 , 120 , 121 , 122 , 123 , 124 , 125 ]. Usually, the key compound implicated in the synthesis of tofacitinib is the (3 R ,4 R )-1-benzyl- N ,4-dimethylpiperidin-3 amine, which is obtained from 3-amino-4-methylpyridine ( Scheme 4 A,B) [ 119 , 120 ] or 4-methyl-picoline ( Scheme 4 C).…”