Disclosed herein is a convenient
Ir-catalyzed amidation of esters
to access α-amido esters. Initially prepared silyl ketene acetals
are directly employed, without separate purification, for subsequent
amidation with an oxycarbonylnitrenoid precursor using the Cp*(LX)Ir(III)
catalyst. The α-amidation was facile for both α-aryl and
α-alkyl esters. Density functional theory studies revealed that
the generation of a putative Ir-nitrenoid is facilitated by the chelation
of the countercation additive during the N–O bond cleavage
of the nitrene precursor.
The Pd‐catalyzed γ‐position sp3−C−H arylation of primary amines bearing an aliphatic chain or cycloalkyl substituent and related mechanistic studies are disclosed. 3‐Bromo‐2‐hydroxybenzaldehyde plays a key role in γ‐position sp3−C−H arylation as a transient directing group (TDG) to assist the regio‐ and stereoselective C−H activation of a Pd catalyst, and the development of a tandem reaction to transform 1°‐amines into γ‐aryl‐substituted ketones demonstrates synthetic utility. Density functional theory (DFT)‐based calculations revealed the detailed reaction mechanism and the origins of the high selectivity (γ‐position and cis‐only). The X‐ray crystal structure of the isolated endo‐palladacycle intermediate supported the DFT results, and a kinetic isotope experiment confirmed the results of DFT calculations indicating that the C−H activation step via simultaneous palladation and deprotonation is rate‐determining.
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