(4-Chloro-7H-pyrrolo[2,3-d]pyrimidin-7-yl)methyl 2,2-dimethylpropanoate ; (4-Chloro-7H-pyrrolo[2,3-d]pyrimidin-7-yl)methyl pivalate;Propanoic acid, 2,2-dimethyl-, (4-chloro-7H-pyrrolo[2,3-d]pyrimidin-7-yl)methyl ester; (4-Chloro-7H-pyrrolo[2,3-d]pyrimidin-7-yl)methyl 2,2-dimethylpropanoate; Baricitinib Impurity 6 (Stage-1)