Palladium‐Catalyzed α‐Arylation Reactions in Total Synthesis (Eur. J. Org. Chem. 1/2015)

Abstract

The cover picture shows the scope of the α‐arylation reaction of carbonyl compounds, such as ketones, aldehydes, esters and amides in the total syntheses of natural products and active pharmaceutical ingredients (API). This is exciting, because α‐arylation reactions have emerged recently as one of the new trends in cross‐coupling reactions, in which the CH at the α position of the carbonyl group undergoes functionalization by enolization in the presence of a base, followed by a C–C coupling under the influence of a metal catalyst, typically Pd. The potential of this powerful methodology will be enormous for key steps in organic synthesis for small and large molecules. Details are presented in the Microreview by T. J. Colacot et al. on .

Recent advances in the synthetic applications of Morita–Baylis–Hillman and Rauhut–Currier adducts of nitroalkenes

“…Very recently, we used the MBH bromides of nitroalkenes 41 in the synthesis of a variety of tetrahydro-α-carbolines 51 by reacting them with tosyliminoindolines 50 (Scheme 16). 26 The reaction involved a cascade double S N 2′ carba-Michael and aza-Michael pathway leading to the formation of tetrahydro-α-carbolines 51 in excellent yields and as a single regioisomer and diastereomer. Various electron-demanding substrates were well tolerated, and the products were formed in good to excellent yields.…”

Enantioselective Synthesis of 3‐Allylindoles from Indolin‐2‐imines and MBH Carbonates via Nucleophilic Catalysis

“…disclosed the synthesis of α‐carbolines via a [3+3] annulation of indolin‐2‐imines and MBH acetates of nitroalkenes in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) with a loading of 200 mol % (Scheme 1A) [16] . With MBH bromides of nitroalkenes as reaction partners, they also reported a formal [3+3] annulation of indolin‐2‐imines for the synthesis of tetrahydro‐α‐carbolines (Scheme 1B) [17] . Notably, an enantioselective [3+3] annulation of indolin‐2‐imines and isatin‐derived MBH carbonates was achieved by He and Han et al.…”

“…[16] With MBH bromides of nitroalkenes as reaction partners, they also reported a formal [3 + 3] annulation of indolin-2-imines for the synthesis of tetrahydro-α-carbolines (Scheme 1B). [17] Notably, an enantioselective [3 + 3] annulation of indolin-2-imines and isatin-derived MBH carbonates was achieved by He and Han et al with the aid of a suitable cinchona-derived Lewis base, giving chiral α-carboline-spirooxindole hybrids (Scheme 1C). [18] Independently, we realized a chiral phosphine catalyzed enantioselective 3-allylation of indolin-2-imines with aldehydederived MBH carbonates for the asymmetric synthesis of 3allylindoles (Scheme 1D).…”