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A chemoselective domino annulation reaction of β-naphthols with methyl aryldiazoacetate is described. The gold catalyst promoted C–H functionalization of β-naphthols, whereas a rhodium or copper complex led to O–H insertion reactions. Consecutive intramolecular lactonization occurred after site-selective alkylation at the 1-position of β-naphthol, providing functionalized naphthofuranone derivatives. The product was transformed into a chiral molecule bearing an all-carbon quaternary stereogenic center with high enantioselectivity.

We previously developed a chemoselective asymmetric phenol dearomatization using a silver catalyst and benzoic acid as an additive to enhance the reaction efficiency. The mechanistic role of the additive, however, remained unclear. Herein we describe detailed studies to elucidate the additive effect, which revealed that benzoic acid plays two supporting roles in the silver-catalyzed reaction. First, it promotes protonation of a silver enolate intermediate to improve the chemical yield of a spirolactam. Second, it dissociates a homochiral dimer of silver phosphate to generate a monomeric species.

Visible light promoted reduction reactions of organohalides, sulfonamides, organonitriles and epoxy ketones were performed using 1,3-dimethylbenzimidazolines possessing 2-hydroxynaphthyl or 2-hydroxyphenyl substituents (HOAr-DMBIH) as photo-reductants. Xe or Hg–Xe lamp through an appropriate glass-filter (λ>390 nm) and a household white light-emitting diode were used as light sources. In these reactions, reductive cleavages of carbon halogen, nitrogen sulfur, carbon carbon (nitrile) and carbon oxygen bonds take place. Bases exert significant effects on the progress of these reactions in a manner that depends on the nature of the substrate. Addition of 1,8-diazabicyclo[5.4.0]undec-7-ene as well as potassium t -butoxide significantly accelerates photo-reduction reactions of organohalides, sulfonamides and organonitriles while the decomposition of formed hydroxy ketones occurs in reactions of epoxy ketones. Single electron transfer from the photo-excited states of benzimidazolines (HOAr-DMBIH) or their deprotonated analogues ( − OAr-DMBIH) to the substrates is proposed to initiate these reactions.

We developed a highly effective organocatalytic system for asymmetric aziridination of cyclic enones. Catalytic asymmetric aziridination of 2-cyclopenten-1-one with t-butyl p-toluenesulfonyloxy carbamate proceeded using 20 mol % of (1R,2R)-1,2-diphenylethylenediamine derivative with an N-4,4-dimethylcyclohexyl group 1h, producing chiral aziridine ketone (1R,5R)-4 in 82% yield with 99% ee. Organocatalyst 1h was also an effective catalyst for the asymmetric aziridination of other cyclic enones. The obtained chiral aziridine ketone (1R,5R)-4 could be successfully transformed into the key intermediate for the synthesis of (−)-allosamizoline, demonstrating the utility of this asymmetric aziridination for the synthesis of aminocyclopentitol derivatives.

A formal synthesis of anatoxin-a was accomplished by using rhodium-catalyzed formal amide insertion reaction. The key reaction was performed on a gram scale using 0.4 mol % of Rh 2 (NHCO t Bu) 4 catalyst, affording a 9-azabicyclo[4.2.1]nonane derivative in good yield. The nitrogen-bridged molecule was converted to Wiseman's intermediate through diastereoselective reduction, site-selective deoxygenation and functional group interconversions.

Various 1-methyl-, 1-triisopropylsilyl-, and 1-benzylindoles are carboxylated under CO2 pressure (3.0 MPa) with the aid of 1.0 molar equiv of Me2AlCl to give 1-substituted indole-3-carboxylic acids in good to excellent yields. Mechanistic studies suggest that the intermediate, an indol-3-ylaluminum ate complex, was reversibly formed by electrophilic addition of Me2AlCl to the substrate followed by deprotonation of the resulting adduct. This method is successfully extended to alkoxycarbonylation with ethyl chloroformate and carbamoylation with naphthalen-1-yl isocyanate, which afford ethyl indole-3-carboxylates and N-naphthalen-1-ylindole-3-carboxamides, respectively.

We previously reported a synthetic method of spirocyclohexadienones using an Pd-catalyzed intramolecular ipso-Friedel–Crafts allylic alkylation of para-substituted phenol derivatives. However, the mechanism for the step leading to spirocyclization and driving force behind the remarkably easier formation of the five-membered spirocyclohexadienone as compared with the six-membered spirocyclohexadienone were unclear. Herein, detailed density functional theory (DFT) calculations for the spirocyclization were performed to obtain a plausible reason for the observed behavior. In addition, the mechanistic basis of the characteristic ortho-selectivity in the related Pd-catalyzed intramolecular Friedel–Crafts allylic alkylation of meta-substituted phenol derivatives was elucidated. DFT calculations and experimental studies revealed that the ortho-selective allylation proceeded via an unexpected eleven-membered oxapalladacycle-mediated intramolecular Friedel–Crafts type process.

A-nor B-aromatic steroidal skeleton was efficiently constructed by means of o -quinodimethane chemistry with exclusive stereoselectivity. The benzocyclobutene substrate for generation of the o -quinodimethane intermediate and subsequent [4+2] cycloaddition could be synthesized via ( E )-selective Julia–Kocienski olefination and diastereoselective Grignard addition reactions. The synthesized tricyclic steroid-like compound with a trans -diol substructure would be utilized for divergent syntheses of potentially antitumor OSW-1 analogues with the truncated steroidal aglycone.

We developed a novel method for synthesizing fused-tricyclic indole derivatives with a 3-aminomethyl indole motif through a reaction cascade involving ipso -Friedel–Crafts alkylation of phenols, rearomatization of the spirocyclohexadienone unit, and iso -Pictet–Spengler reaction. Using TFA as an acid promoter, six-, seven-, and eight-membered ring-fused indoles were obtained in 31–99% yield.

Formal meta-specific intramolecular Friedel–Crafts allylic alkylation of phenols was achieved based on spirocyclization–dienone–phenol rearrangement cascades. Systematic screening of acid catalysts revealed that Sc(OTf)3 was a highly effective catalyst for dienone–phenol rearrangement of spiro[4.5]cyclohexadienones. Using 5 mol % of Sc(OTf)3 as the promoter, various spirocyclic substrates were transformed into the corresponding phenol derivatives in good to excellent yield. Furthermore, the one-pot sequential spirocyclization–dienone–phenol rearrangement proceeded using a palladium and scandium multi-catalytic system or a triphenylmethyl cation single-catalyst system, providing the corresponding meta-allylated phenol derivatives in excellent yield.

Simplified des-AB-type aglycone of antitumor steroidal saponin OSW-1 was concisely prepared starting from readily available Hajos ketone. We further completed the synthesis of des-AB-OSW-1 analogue by the installation of the disaccharide moiety into the des-AB aglycone, and evaluated its antitumor activity. The results indicated that a truncated aglycone drug design strategy based on OSW-1 would be a promising approach for the development of novel antitumor agents.

We report the first enantioselective total syntheses of cedrelin A and methylated paralycolin B, wherein Pd-catalyzed asymmetric intramolecular Friedel–Crafts allylic alkylation of phenols was the key step.

Highly regio- and stereoselective carbon–carbon bond formation reaction of vinylaziridines using a masked acyl cyanide reagent possessing a tert-butyldimethylsilyl group occurred in the presence of a catalytic amount of palladium complex in excellent yield. It is considered that these excellent selectivities are the result of three simultaneous conditions, strained leaving group, small nucleophile, and ligand with small cone-angle.