Low‐Valent Cobalt‐Catalyzed Deprotection of Allyloxyarenes

Abstract

Herein, we report a low‐valent cobalt‐catalyzed deprotection of allyloxyarenes. The method displays a broad substrate scope and good functional group tolerance, granting its utilization on more complex substrates, including O‐allylated derivatives of natural products and drugs. Based on comprehensive experiments, a plausible mechanistic pathway for the low‐valent cobalt‐catalyzed O‐deallylation of allyloxyarenes is proposed.

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

“…Firstly, the highly reactive α‐halo carbonyls could generate the nucleophilic Reformatsky reagent in the presence of a metal reductant, thus often proceeding the classic Reformatsky‐type background reaction with ketimine [16] . Secondly, α‐carbonyl 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.…”

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.…”

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

“…该设想的难点在于, 如何调控 α-卤代羰基化合物的 反应性和选择性. 在金属还原剂的存在下, α-卤代羰基 化合物很容易生成亲核 Reformatsky 试剂, 这会与酮亚 胺发生经典的 Reformatskii 型背景反应, 从而不可避免 地降低自由基对碳氮双键加成过程中的对映选择性 [9] . 该课题组通过不同 α-卤代的羰基化合物生成 Reformatsky 试剂的活性差异来调控反应途径, α-氯代的羰基化 合物活性较低, 难以生成 Reformatsky 试剂, 由此可避 免经典的 Reformatskii 型背景反应, 从而使得该反应几 乎完全以 α-羰基自由基对碳氮双键加成的途径进行 (Scheme 2) [10] .…”