Construction of spirocarbocycles via gold-catalyzed intramolecular dearomatization of naphthols

A highly efficient, gold-catalyzed intramolecular dearomatization reaction of naphthols via 5-endo-dig cyclization is described. This facile and direct approach furnishes spirocarbocycles in excellent yields under mild conditions.

Enantioselective Synthesis of Chiral Piperidines via the Stepwise Dearomatization/Borylation of Pyridines

We have developed a novel approach for the synthesis of enantioenriched 3-boryl-tetrahydropyridines via the Cu(I)-catalyzed regio-, diastereo-, and enantioselective protoborylation of 1,2-dihydropyridines, which were obtained by the partial reduction of the pyridine derivatives. This dearomatization/enantioselective borylation stepwise strategy provides facile access to chiral piperidines together with the stereospecific transformation of a stereogenic C-B bond from readily available starting materials. Furthermore, the utility of this method is demonstrated for the concise synthesis of the antidepressant drug (-)-paroxetine. A theoretical study of the reaction mechanism is also described.

New opportunities in the stereoselective dearomatization of indoles

The regio- and stereoselective dearomatization of indoles is realized for the first time by combining readily available indolyl precursors and electron-rich allenes, namely allenamides and aryloxyallenes. Inter- as well as intramolecular condensations were realized under gold and Brønsted acid catalysis providing a range of densely functionalized indoline and indolenine cores in high yields and excellent stereochemical outcome. Chemodivergent reaction profiles (Micheal-type addition vs. [2+2]-cycloaddition) were realized by a tailored design of both reaction conditions and functionalization of the reaction partners.

Synthesis of Enantioenriched Indolines by a Conjugate Addition/Asymmetric Protonation/Aza-Prins Cascade Reaction

A conjugate addition/asymmetric protonation/aza-Prins cascade reaction has been developed for the enantioselective synthesis of fused polycyclic indolines. A catalyst system generated from ZrCl4 and 3,3'-dibromo-BINOL enables the synthesis of a range of polycyclic indolines in good yields and with high enantioselectivity. A key finding is the use of TMSCl and 2,6-dibromophenol as a stoichiometric source of HCl to facilitate catalyst turnover. This transformation is the first in which a ZrCl4 ⋅BINOL complex serves as a chiral Lewis-acid-assisted Brønsted acid.

Visible-light-induced aerobic dearomative reaction of indole derivatives: access to heterocycle fused or spirocyclo indolones

Oxazolo[3,2-a]indolone and spiro[furan-2,2'-indolin]one are synthesized by the visible-light-induced aerobic dearomative reaction of indoles. The common indole tethered alcohol at the N1 or C2 position reacts in a cascade fashion, providing facile access to diverse indolone scaffolds.

Chemo-, Diastereo-, and Enantioselective Iridium-Catalyzed Allylic Intramolecular Dearomatization Reaction of Naphthol Derivatives

An iridium-catalyzed intramolecular asymmetric allylic dearomatization reaction of naphthol derivatives is described. Challenges confronted in this reaction include chemoselectivity between carbon and oxygen atoms as nucleophilic centers, diastereoselectivity when contiguous chiral centers are generated, and enantioselective control for constructing an all-carbon quaternary stereocenter. In the presence of an iridium catalyst generated from [{Ir(dbcot)Cl}2] (dbcot=dibenzocyclooctatetraene) and a new THQphos (tetrahydroquinolinedinaphthophosphoramidite) ligand, various spironaphthalenones were obtained with up to greater than 95:5 C/O selectivity, greater than 95:5 d.r., and 99 % ee, thus providing a general method for the dearomatization of naphthols.

Synthesis of 3-alkyl spiro[4,5]trienones by copper-catalyzed oxidative ipso-annulation of activated alkynes with unactivated alkanes

A Cu-catalyzed oxidative ipso-annulation of activated alkynes with unactivated alkanes for the synthesis of 3-alkyl spiro[4,5]trienones is described. This method allows the formation of two carbon-carbon bonds and one carbon-oxygen bond in a single reaction through a sequence of C-H oxidative coupling, ipso-carbocyclization and dearomatization.

Chiral Triazoles in Anion-Binding Catalysis: New Entry to Enantioselective Reissert-Type Reactions

Easily accessible and tunable chiral triazoles have been introduced as a novel class of C-H bond-based H-donors for anion-binding organocatalysis. They have proven to be effective catalysts for the dearomatization reaction of different N-heteroarenes. Although this dearomatization approach represents a powerful strategy to build chiral heterocycles, to date only a few catalytic methods to this end exist. In this work, the organocatalyzed enantioselective Reissert-type dearomatization of isoquinoline derivatives employing a number of structurally diverse chiral triazoles as anion-binding catalysts was realized. The here presented method was employed to synthesize a number of chiral 1,2-dihydroisoquinoline substrates with an enantioselectivity up to 86:14 e.r. Moreover, a thorough study of the determining parameters affecting the activity of this type of anion- binding catalysts was carried out.

PhSeBr mediated hydroxylative oxidative dearomatization of naphthols – an open air facile one-pot synthesis of ketols

A facile open air methodology for oxidative dearomatisation of planar naphthols is described.

A convenient method for the synthesis of α-carboxylate ester bromolactones via bromolactonization of alkenoic diesters

A simple and efficient synthesis of α-ester bromolactones has been developed through the electrophilic bromocyclization of olefinic 1,3-diesters.

[3 + 2]-Annulations of N-alkyl-3-substituted indoles with quinone monoketals catalysed by Brønsted acids

An organocatalytic dearomative [3 + 2]-annulation of 3-alkylindoles and quinone monoketals provided benzofuro[2,3-b]indolines, while the reaction with 3-phenylindole leads to 2,3-diarylindoles in moderate yields.

Catalytic asymmetric dearomatization (CADA) reactions of phenol and aniline derivatives

In this tutorial review, an up to date summary of recent progress in catalytic asymmetric dearomatization (CADA) reactions of phenol and aniline derivatives is presented.

Palladium-catalyzed reductive Heck-type vinylative dearomatization of unfunctionalized halonaphthalene derivatives

A novel strategy for the dearomatization of inactive 1-halonaphthalenes via palladium-catalyzed reductive Heck-type vinylative reaction was successfully developed.

Asymmetric dearomatization of phenols

This review summarizes the recent advances in the field of asymmetric dearomatization of phenols and their applications in the total synthesis of some complex natural products.

Palladium-catalyzed dearomative arylalkynylation of indoles

A palladium-catalyzed indole dearomative bisfunctionalization via a domino arylation/alkynylation sequence to achieve tetracyclic indolines bearing vicinal tertiary and quaternary stereocenters.

Decarboxylative dearomatization and mono-α-arylation of ketones

Ligand-controlled decarboxylative coupling of benzyl enol carbonates provides dearomatized products via enantiospecific coupling or alpha-aromatic ketones via dearomatization–rearomatization.

Aryne-induced dearomatized phosphonylation of electron-deficient azaarenes

Aryne-induced dearomatic phosphonylation of electron-deficient azaarenes.

Rapid assembly of spirocycles with phenol-derived biaryls with alkynes using an oxidative C–H activation/dearomatization strategy

The synthesis of spirocyclohexadienones from phenol-derived biaryls was accomplished by using a transition-metal-catalyzed C–H activation/dearomatization strategy.

Enantioselective dearomative [3 + 2] cycloadditions of indoles with azomethine ylides derived from alanine imino esters

Dearomative cycloadditions of imino esters derived from alanine with 3-nitroindoles form exo′-pyrroloindolines in good yields with high diastereo- and enantioselectivities.

Addition of 4-(cyclohex-1-en-1-yl)morpholine on 3-nitroindole: an unprecedented dearomatizing process

Nucleophilic enamine2aadd spontaneously on nitroindole1to form a dearomatized formal ene adduct3a.

Asymmetric nucleophilic dearomatization of diazarenes by anion-binding catalysis

The first highly regio- and enantioselective nucleophilic dearomatization of diazarenes by anion-binding organocatalysis is reported.

Dearomatization of Indoles via Palladium-Catalyzed Allylic C-H Activation

The first Pd-catalyzed allylic dearomatization of substituted indoles triggered by C-H bond activation is reported. The presence of a catalytic amount of 2,5-DMBQ is proven to be a key factor for the high yield. This one-pot tandem allylic C-H activation/dearomatization sequence provides a straightforward access to 3,3-disubstituted indolines.

Iridium-Catalyzed Intramolecular Asymmetric Allylic Dearomatization Reaction of Pyridines, Pyrazines, Quinolines, and Isoquinolines

The first Ir-catalyzed intramolecular asymmetric allylic dearomatization reaction of pyridines, pyrazines, quinolines, and isoquinolines has been developed. Enabled by in situ formed chiral Ir-catalyst, the dearomatized products were isolated in high levels of yield (up to 99% yield) and enantioselectivity (up to 99% ee). It is worth noting that the Me-THQphos ligand is much more efficient than other tested ligands for the dearomatization of pyrazines and certain quinolines. Mechanistic studies of the dearomatization reaction were carried out, and the results suggest the feasibility of an alternative process which features the formation of a quinolinium as the key intermediate. The mechanistic findings render this reaction a yet unknown type in the chemistry of Reissert-type reactions. In addition, the utility of this method was showcased by a large-scale reaction and formal synthesis of (+)-gephyrotoxin.