Li-Xin Dai

Iridium-Catalyzed Allylic Vinylation and Asymmetric Allylic Amination Reactions with o-Aminostyrenes

An Ir-catalyzed allylic vinylation reaction of allyl carbonates with o-aminostyrene derivatives has been realized, providing skipped (Z,E)-diene derivatives. With (E)-but-2-ene-1,4-diyl dimethyl dicarbonate as the substrate, an efficient enantioselective synthesis of 1-benzazepine derivatives via an Ir-catalyzed domino allylic vinylation/intramolecular allylic amination reaction has been developed. Mechanistic studies of the allylic vinylation reaction have been carried out, and the results suggest that the leaving group of the allylic precursor plays a key role in directing the reaction pathway. Screening of various allylic precursors showed that Ir-catalyzed reactions of allyl diethyl phosphates with o-aminostyrene derivatives proceed via an allylic amination pathway. A subsequent ring-closing metathesis (RCM) reaction of the amination products led to a series of enantiomerically enriched 1,2-dihydroquinoline derivatives. Their utility is indicated by an asymmetric total synthesis of (-)-angustureine.

Iridium-Catalyzed Allylic Alkylation Reaction with N-Aryl Phosphoramidite Ligands: Scope and Mechanistic Studies

A series of N-aryl phosphoramidite ligands has been synthesized and applied to iridium-catalyzed allylic alkylation reactions, offering high regio- and enantioselectivities for a wide variety of substrates. These ligands feature the synthetic convenience and good tolerance of the ortho-substituted cinnamyl carbonates. Mechanistic studies, including DFT calculations and X-ray crystallographic analyses of the (π-allyl)-Ir complexes, reveal that the active iridacycle is formed via C(sp(2))-H bond activation.

Palladium(0)-catalyzed dearomative arylation of indoles: convenient access to spiroindolenine derivatives.

Dearomatization of an indole via palladium(0)-catalyzed cross-coupling reaction has been realized. With readily available triphenylphosphine as ligand, various spiroindolenine derivatives have been obtained in good to excellent yields, and enantioselective control is also feasible with chiral ligands.

Desymmetric ring-opening of meso-epoxides with anilines: a simple way to chiral β-amino alcohols

Abstract Chiral β-amino alcohols were afforded by desymmetric ring-opening of meso -epoxides with anilines catalyzed by chiral Yb triflate complex in up to 80.1% ee.

Ir-Catalyzed Regio- and Enantioselective Friedel–Crafts-Type Allylic Alkylation of Indoles

Highly regio- and enantioselective Ir-catalyzed Friedel-Crafts type allylic alkylation of indoles have been realized using [Ir(COD)Cl]2/phosphoramidite ligand 1a, affording the branched products with up to >97/3 branched-linear ratio and 92% ee.

Iridium-Catalyzed Asymmetric Allylic Substitutions

Ir-catalyzed asymmetric allylic substitution reactions have been reviewed. This chapter discusses respectively the mechanistic investigation, reaction scope, and synthetic application of Ir-catalyzed allylic substitution reactions. The reaction scope is classified according to different types of nucleophiles such as C, N, O, and S.

Diversity oriented synthesis of indole-based peri-annulated compounds via allylic alkylation reactions

Diverse indole-based peri-annulated compounds were synthesized via transition-metal-catalyzed allylic alkylation reaction. With palladium catalyst, indole-based nine-membered ring products were obtained in 40–70% yields. When iridium catalyst was used, highly enantioenriched seven-membered ring products were obtained in 40–78% yields and 91–97% ee. Meanwhile, when 3-substituted indole substrates were employed with a palladium catalyst, asymmetric allylic dearomatization of indoles occurred with products obtained in 48–78% yields and 35–78% ee with a chiral ferrocene-based Phox ligand. Interestingly, with an iridium catalyst, Friedel–Crafts type allylic alkylation reaction proceeded at the C5 position of indole, affording the products with 40–60% yields and 56–97% ee.

N-Heterocyclic Carbene Catalyzed Ring Expansion of Formylcyclopropanes: Synthesis of 3,4-Dihydro-α-pyrone Derivatives

N-Heterocyclic carbene catalyzed ring expansion of readily accessible 2-acyl-1-formylcyclopropanes was developed. With 5 mol % of triazolium salt 5 and 30 mol % of DBU, ring expansion of various 2-acyl-1-formylcyclopropanes led to 3,4-dihydro-alpha-pyrones in good to excellent yields.

Copper(I)-catalyzed cascade dearomatization of 2-substituted tryptophols with iodonium [corrected] salts.

Copper(I)-catalyzed dearomative arylation and vinylation of 2-substituted tryptophols were realized with a subsequent cyclization reaction. The cascade dearomatization sequence provided versatile furoindoline derivatives with two quaternary carbon centers in good to excellent yields.

Stereoselective synthesis of three-membered ring compounds via ylide routes

Three types of small ring compounds (epoxides, aziridines and cyclopropanes) can be synthesized stereoselectively via ylide route. Among them, the stereochemistry of vinyloxiranes, vinylaziridines, cyclopropylesters, amides and ketones can be tuned by the choice of reaction conditions and ylides with varying heteroatoms and ligands. Optically active epoxides and acetylenylaziridines can be prepared via camphor-derived chiral sulfonium ylide routes.