Strategies for Carbon Electrophile Addition to Carbonyls and Imines by Cobalt Catalysis

Abstract

The addition of carbon electrophiles to carbonyls and imines has emerged as a valuable strategy for the construction of C‐C bonds. The merger of this concept with sustainable cobalt catalysis has yielded numerous innovative methodologies. Remarkable functional group tolerance and selectivity have been observed in many cases, providing reliable methods for bond construction. The cobalt‐catalyzed additions of carbon electrophiles to carbonyls, imines and carboxylic acid derivatives described in this review include the earliest reports, such as Takai‐Utimoto Co/Cr co‐catalyzed additions and their progression, as well as modern variants, exemplified by recent Co/photoredox co‐catalyzed protocols. The systematic appraisal of this modern strategy provides a clearer perspective and inspiration for its further development.

Cobalt‐Catalyzed Enantioselective Reductive α‐Chloro‐Carbonyl Addition of Ketimine to Construct the β‐Tertiary Amino Acid Analogues

“…[16] Secondly, αcarbonyl radical intermediate under the reductive conditions may undergo direct radical addition to C=N bond. [17] Both the abovementioned side pathways would inevitably diminish the enantioselectivities in the realm of stereoselective addition process. To overcome the aforementioned challenges, we envision that the leverage of α-halocarbonyl compounds with moderate activity might circumvent the formation of Reformatsky reagent to generate an α-carbonyl radical, and the subsequent engagement of the radical species in the addition process towards C=N bond might be modulated by the earth-abundant cobalt catalyst, thus accomplishing the differentiation the enantiotopic face of ketimine to achieve the high enantioselectivity.…”