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Bis(2-pyridyl)amides as Readily Cleavable Amides Under Catalytic, Neutral, and Room-Temperature Conditions

Abstract

Mild solvolytic cleavage of bis(2-pyridyl)amide under neutral and room-temperature conditions is described. The inherently stable amide was readily activated by catalytic amounts of metal cations to react with alcohols. Based on X-ray crystallographic analysis, the primary driving force was considered to be amide distortion induced by the metal coordination of two pyridyl groups in a bidentate fashion without affecting the amide functionality. The compatibility of the acid/base-sensitive functionalities and the absence of racemization during solvolysis highlight the mildness of the present protocol.

Key words

amide - deconjugation - amide distortion - amide twisting - solvolysis - metal coordination - mild conditions

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• 18 See Supporting Information.
• 19 Other designed amide cleavable by stoichiometric amount of Zn(OTf)₂ was developed. See ref. 15j.
• 20 A part of the crsytal structure was disordered. See Supporting Information.

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• 22 General Procedure: Catalytic Solvolysis of Amide 6 A flame-dried 5 mL round-bottomed flask equipped with a magnetic stirring bar and a septum cap was charged with amide 6 (0.20 mmol) and Zn(OTf)₂ (0.01 mmol, 5 mol% or 0.004 mmol, 2 mol%; 0.02 mmol, 10 mol% or 0.01 mmol, 5 mol% of Cu(OTf)₂ were used for the synthesis of 7ac or 7c, respectively) in a glove box under Ar atmosphere. After adding anhydrous MeOH (2.0 mL; 2 mL of EtOH or ⁱ PrOH was used for the synthesis of 7ab or 7ac) at rt, the resulting clear solution was stirred for designated period of reaction time at the same temperature. The reaction mixture was concentrated under reduced pressure, and the resulting residue was purified by flash column chromatography to give esters 7. Methyl cinnamate (7a): white solid; yield 29.7 mg (92%). Ethyl cinnamate (7ab): colorless oil; yield 33.5 mg (95%). Isopropyl Cinnamate (7ac): colorless oil; yield 26.9 mg (71%). Methyl 4-[(tert-butoxycarbonyl)amino]benzoate (7b): white solid; yield 41.4 mg (82%). Methyl 4-(methoxymethoxy)benzoate (7c): clorless oil; yield 35.9 mg (91%). Methyl 4-[(tert-butyldimethylsilyl)oxy]benzoate (7d): colorless oil; yield 51.2 mg (96%). tert-Butyl methyl terephthalate (7e): white solid; yield 42.8 mg (91%). Methyl picolinate (7f): colorless oil; yield 26.7 mg (97%). Methyl 4-oxo-4-phenylbutanoate (7g): colorless oil; yield 36.4 mg (95%). (S)-Methyl 2-({[(9H-fluoren-9-yl)methoxy]carbonyl}amino) propanoate (7h): white solid; yield 57.6 mg (89%).
• 23 Determined by HPLC analysis.