Highly Enantioselective Iridium-Catalyzed Cascade Double Allylation Strategy: Synthesis of Pyrrolidinoindolines with an All-Carbon Quaternary Stereocenter

Asymmetric cascades of the π-allyl complex: a journey from transition-metal catalysis to metallaphotocatalysis

The enantioselective catalytic cascade involving Tsuji-Trost allylation has provided a viable strategy for the construction of multiple asymmetric C-C and C-X centres and numerous methods have been developed around it for the synthesis of various vital scaffolds. The synthetic utility of this strategy was enhanced by replacing the customary allyl acetates with ethylene diacetates/dicarbonates, vinyl epoxides, vinyl oxetanes, vinyl ethylene carbonates, vinyl cyclopropanes, enynes, and dienes using transition-metal catalysis. One more milestone was achieved when metallaphotocatalysis provided the necessary platform for these cascades by using a cheaper metal. This review will provide a summary of these enantioselective catalytic cascades from 2015.

Pd-Catalyzed Asymmetric Annulative Dearomatization of Phenols for Regio- and Enantioselective Synthesis of Spirocyclohexadienones

A palladium-catalyzed asymmetric annulative dearomatization of phenols with butene dicarbonate is reported, enabling twofold decarboxylative allylation to regioselectively produce a range of spirocyclohexadienones with 29-95% yields and 74-99% ee. A catalytic dearomative formal [4 + 2] cyclization of 1,1'-biphenyl-2,4'-diols delivered spiro[chromane-4,1'-cyclohexane]-2',5'-dien-4'-ones with high enantioselectivity, whereas enantioenriched spiro[cyclohexane-1,4'-quinoline]-2,5-dien-4-ones were generated starting from 2'-amino-[1,1'-biphenyl]-4-ols as 1,4-dinucleophiles.

Regio- and Enantioselective Synthesis of Dihydropyrido[1,2-a]indoles via Catalytic Asymmetric Annulative Allylic Alkylation

A palladium-catalyzed asymmetric annulative allylic alkylation reaction of 2-[(1H-indol-2-yl)methyl]malonates with (E)-but-2-ene-1,4-diyl dicarbonates is described, leading to the regio- and enantioselective synthesis of dihydropyrido[1,2-a]indoles with a chiral cyclic allyl stereocenter adjacent to the ring-junction nitrogen atom in moderate to good yields. The salient features of this protocol include mild conditions, a broad substrate scope, and good compatibility with substituents as well as high regio- and stereoselectivities, providing a catalytic asymmetric entry for fabricating chiral pyridoindole scaffolds.

Enantioselective Synthesis of Functionalized Tetrahydropyridines through Iridium-Catalyzed Formal [5+1] Annulation

An efficient iridium-catalyzed asymmetric formal [5+1] annulation by in situ generation of enamines as N-nucleophiles for the synthesis of tetrahydropyridine derivatives is disclosed. The methodology offers direct access to a wide variety of chiral tetrahydropyridine derivatives in moderate to good yields and excellent enantioselectivity.

Recent advances in iridium-catalyzed enantioselective allylic substitution using phosphoramidite-alkene ligands

This minireview describes the recent progress of iridium-catalyzed enantioselective allylic substitution using phosphoramidite-alkene ligands realizing highly enantioselective carbon–carbon and carbon–heteroatom bond formation.

Palladium-catalyzed [3 + 3] annulations of 1-alkyl-indolin-2-imines and dialkyl (2-methylenepropane-1,3-diyl) dicarbonates

Palladium-catalyzed [3 + 3] annulations of 1-alkyl-indolin-2-imines and dialkyl (2-methylenepropane-1,3-diyl) dicarbonates leading to pyrido[2,3-b]indole derivatives have been developed for the first time.

Access to Polycyclic Thienoindolines via Formal [2+2+1] Cyclization of Alkynyl Indoles with S8 and K2S

The syntheses of polycyclic thienoindolines bearing a dihydrothiophene or tetrahydrothiophene subunit have not been reported, despite the fact that such compounds may have interesting medicinal properties. Herein, we report a protocol for accessing polycyclic dihydrothiophenes by means of formal [2+2+1] intramolecular dearomatizing cyclization of alkynyl indoles with K₂S and S₈ as the sources of sulfide. In addition, tetrahydrothienoindolines were stereoselectively synthesized via a one-pot, two-step protocol involving AgNO₃-catalyzed alkenyl dearomatization followed by two nucleophilic addition reactions involving K₂S.

Catalytic asymmetric preparation of pyrroloindolines: strategies and applications to total synthesis

Pyrroloindolines are widely present in natural products. In this review, we summarize state-of-the-art of catalytic asymmetric synthesis of pyrroloindolines, as well as related applications to natural products total synthesis.