Base-Promoted Deprotection of tert-Butyl 4-(1-(3-(cyanomethyl)-1-(ethylsulfonyl)azetidin-3-yl)-1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidine-7carboxylate: Preservation of a Nitrile Functional Group under Mild Conditions

The tert-butoxycarbonyl (Boc) protecting group is one of the most widely employed amineprotecting groups in organic synthesis due to its ease of installation and reliable removal under acidic conditions. However, conventional acid-mediated Boc deprotection can be incompatible with acid-sensitive functional groups such as nitriles, often leading to partial hydrolysis, decomposition, or undesired side reactions in complex molecular frameworks. In this study, we report a mild and efficient base-promoted strategy for the selective removal of a Boc group from tert-butyl 4-(1-(3-(cyanomethyl)-1-(ethylsulfonyl)azetidin-3-yl)-1H-pyrazol-4-yl)-7Hpyrrolo[2,3-d]pyrimidine-7-carboxylate while fully preserving the nitrile functionality. The deprotection proceeds smoothly using cesium carbonate in MeOH under reflux conditions, affording the desired free amine in excellent yield (>90%) and high purity (>99% by HPLC). No degradation of the nitrile group or heterocyclic core was observed. This method offers high chemoselectivity, operational simplicity, and broad applicability for the synthesis and late-stage functionalization of complex molecules bearing acid-sensitive groups, particularly in pharmaceutical and medicinal chemistry contexts.