The combination of transition-metal catalysis and organocatalysis increasingly offers chemists opportunities to realize diverse unprecedented chemical transformations. By combining iridium with chiral thiourea catalysis, direct enantioselective reductive cyanation and phosphonylation of secondary amides have been accomplished for the first time for the synthesis of enantioenriched chiral a-aminonitriles and aaminophosphonates. The protocol is highly efficient and enantioselective, providing a novel route to the synthesis of optically active a-functionalized amines from the simple, readily available feedstocks. In addition, the reactions are scalable and the thiourea catalyst can be recycled and reused.
N-Acylpyrrole-type amides are a class of versatile building blocks in asymmetric synthesis. We report that by employing Ni(COD) 2 /2,2′-bipyridine (5 mol%) catalytic system, the direct, catalytic alcoholysis of N-acylpyrrole-type aromatic and aliphatic amides with both primary and secondary alcohols can be achieved efficiently under very mild conditions (rt, 1 h) even at gram scale. By increasing the catalyst loading to 10 mol%, prolonging reaction time (18 h), and/or elevating reaction temperature to 50°C/80°C, the reaction could be extended to both complex and hindered N-acylpyrroles as well as to N-acylpyrazoles, Nacylindoles, and to other (functionalized) primary and secondary alcohols. In all cases, only 1.5 equiv. of alcohol were used. The value of the method has been demonstrated by the racemization-free, catalytic alcoholysis of chiral amides yielded from other asymmetric methodologies.
A novel C(sp3)–H bond arylation of tetrahydroisoquinoline (THIQ) derivatives with Knochel-type arylzinc reagents has been developed. In the presence of MgCl2, arylzinc reagents readily reacted with THIQ derivatives under oxidative conditions, affording a wide range of potentially biologically active compounds in good yields. Moreover, the developed method can tolerate a variety of sensitive functional groups such as an ester group.
Summary of main observation and conclusion
The efficient construction of functionalized polycyclic structures is an important objective in organic synthesis. Herein, we disclose a three‐step “[2 + n]” annulation method for the transformation of cyclic ketones to fused enimines and enones. The method relies on the Suzuki coupling reaction and the amide reductive alkenylation reaction. A series of fused bicyclic (6/6, 6/7, 8/7) and tricyclic (6/6/6; 6/6/7, 6/5/7) ring systems bearing an α,β‐enimine or an α,β‐enone functionality have been synthetized in good overall yields.
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