Feedstock Reagents in Metal‐Catalyzed Carbonyl Reductive Coupling: Minimizing Preactivation for Efficiency in Target‐Oriented Synthesis

Abstract

Use of abundant feedstock pronucleophiles in catalytic carbonyl reductive coupling enhances efficiency in target‐oriented synthesis. For such reactions, equally inexpensive reductants are desired or, ideally, corresponding hydrogen autotransfer processes may be enacted wherein alcohols serve dually as reductant and carbonyl proelectrophile. As described in this Minireview, these concepts allow reactions that traditionally require preformed organometallic reagents to be conducted catalytically in a byproduct‐free manner from inexpensive π‐unsaturated precursors.

Rhodium‐Catalyzed Dealkenylative Arylation of Alkenes with Arylboronic Compounds

“…When Ag 2 Ow as replaced with Ag 2 CO 3 as oxidant, 3a was delivered in as lightly decreased yield (Table S1, entry 7) and the reaction was shut down completely when employing AgOAc and Cu(OAc) 2 as oxidant (Table S1, entries 8a nd 9). Moreover,s olvents also significantly affect the chemoselectivity (Table S1, entries [10][11][12][13][14][15]. Fore xample, CF 3 CH 2 OH gave am oderate yield of 3a along with at race amount of the by-product 3aa.However,the undesired Heck arylation was more favored when employing other solvents such as MeOH, t BuOH, DCE, 1,4-dioxane,a nd toluene.…”

“…Based on the above observations and relevant literature, [10,14,15] ap lausible mechanistic pathway is proposed as Table 2: Scope of directing group-containing alkenes. [a,b] [a] Reaction conditions: 1 (0.…”

Rhodium‐katalysierte dealkenylierende Arylierung von Alkenen mit Arylboronverbindungen

“…Basierend auf den oben genannten Beobachtungen und der einschlägigen Literatur [10,14,15] wird ein plausibler mechanistischer Wegv orgeschlagen, wie in Schema 3d argestellt. Erstens bildet die Reaktion von [RhCp*(MeCN) 3 ][SbF 6 ] 2 mit EtOH eine aktive Katalysatorspezies [Cp*Rh III X]-H (X = SbF 6 oder OEt) zusammen mit CH 3 CHO (CH 3 CHO wurde durch GCMS nach der Reaktion von 1e und 2a nachgewiesen, siehe Hintergrundinformationen).…”

Catalytic Asymmetric Addition and Telomerization of Butadiene with Enamine Intermediates

“…1.3 × 10 7 tons, butadiene appears as an ideal starting material for chemical synthesis in the pursuit of atom-economic value-added production. 32,33 For this end, transition metal catalysts have been explored and carefully tuned to enable selective C-C bond formation reactions of butadiene and meanwhile to suppress the undesired polymeric pathways. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] It's known that butadiene can participate in crotylation, [34][35][36][37][38][39][40] 1,2-or 1,4-addition [41][42][43] and telomerization [41][42][43][44] (Scheme 1, I).…”

“…Previously, monophosphine ligand was shown to mediate a racemic telomerization process via an enol mechanism. 33,[38][39][40] Monophosphine ligand was then screened in current asymmetric enamine process (Table 1, entries 8 and 10-14). To our delight, the reaction in the presence of tri-ptolylphosphine was found to afford exclusively the desired telomerization product 5a with 80% yield and 93% ee (Table 1, entry 8).…”