Regioselective Oxidative C–H Phosphonation of Imidazo[1,2‐a]pyridines and Related Heteroarenes Mediated by Manganese(III) Acetate

Abstract

Herein, we report a MnIII‐mediated regioselective method for the direct C–H phosphonation of imidazo[1,2‐a]pyridines by using dialkyl phosphites. 3‐Phosphonated imidazo[1,2‐a]pyridines are synthesized in good to excellent yields under the optimized reaction conditions. The present method is also applicable to the functionalization of related heteroarenes, and unlike previously reported methods, the present strategy works well with (NH)‐heteroarenes.

Ring‐Opening Reaction of Imidazo[1,2‐a]pyridines Using (Diacetoxyiodo)benzene and NaN3: The Synthesis of α‐Iminonitriles

“…Functionalization at the C3 position is one of the most common strategies to form structurally diverse imidazo[1,2‐ a ]pyridines. Methods for the fluorination, thiocyanation, sulfenylation, selenylation, nitrosylation, phosphonation, arylation, alkenylation, carbonylation, formylation, and trifluoromethylation were recently developed for functionalization at the C3 position of imidazo[1,2‐ a ]pyridines. The introduction of such a variety of functional groups at this position has been accomplished by employing oxidants such as CuI, Cu(OAc) 2 , Mn(OAc) 3 , K 2 S 2 O 8 , molecular iodine, and N ‐chlorosuccinimide.…”

Recent Advances in the Construction of Phosphorus‐Substituted Heterocycles, 2009–2019

“…The direct functionalization of imidazole[1,2‐ a ]pyridine frameworks was considered as an efficient route to imidazole[1,2‐ a ]pyridine derivatives that were of great value in medicinal chemistry. Recently, an Mn(III)‐mediated regioselective C‐3 phosphonation of the C−H bond of imidazo[1,2‐ a ]pyridines has been established by the Singh group to access 3‐phosphonated imidazo[1,2‐ a ]pyridines . After extensive optimization of the reaction conditions, Mn(OAc) 2 ⋅2 H 2 O was found to be effective for promoting this reaction, furnishing the desired products 83 in moderate to good yields (Scheme ).…”

Recent Advances in Radical C−H Bond Functionalization of Imidazoheterocycles

“…[70] In 2015, Singh and his group reported a Mn(III)mediated regioselective phosphonation of imidazo[1,2a]pyridines 1 using dialkyl phosphites 74 in NMP at 80°C (Scheme 47). [71] A series of 3-phosphonated imidazo[1,2-a]pyridines 75 was prepared by the reaction of various substituted imidazo[1,2-a]pyridines 1 with dialkyl phosphites 74. The developed method was also applicable for other related N-heterocycles such as indoles, azaindoles and pyrroles under standard reaction conditions, which provided the desired products in 40-82% yields.…”