Dinucleophilic Reactivity of Isocyanoacetate: Base-Catalyzed One-Pot Access to 4-Azafluorenes and 4-Azafluorenones

Rh-Catalyzed and Self-Directed Aromatic C-H Activation of Enaminones to Divergent Alkenylated and Annulated Compounds

By means of simple Rh catalysis, the direct activation of the ortho-C-H bond in aryl enaminones has been realized with the enaminone structure as a traceless directing fragment. The products resulting from C-H alkenylation and further annulation via intramolecular C-H bond addition could be accessed depending upon the structure of alkenes. The annulated products could be used for the easy synthesis of valuable 2-aza-fluorenones in a one-pot operation by employing NH4OAc.

Synthesis of CF3-Azafluorenes through the Cascade Reaction of 2H-Imidazoles with CF3-Ynones

A concise synthesis of trifluoromethyl (CF3)-substituted azafluorenes based on the reaction of 5-aryl-2H-imidazoles with CF3-ynones is reported. The reaction proceeds through C-H activation-initiated formal [3+2] cycloaddition to give spiro[imidazole-4,1'-indene] as a key intermediate, followed by its retro [3+2] cycloaddition, isomerization, and enamine nucleophilic addition. This synthesis of CF3-azafluorene derivatives via simultaneous formation of both the indene and the pyridine scaffolds through cascade C-H/C-C/C-N bond cleavage and C≡C bond formation has not been disclosed before. Moreover, the products thus obtained showed antiproliferative activity against cancer cell lines.

[1,5]-Oxy/Thio/Azole Sigmatropic Rearrangement versus Indolyl-Spirocyclization: Tandem Reactions of 2-Azidobenzoate with Isocyanides for Accessing Quinazolin-4(3H)-ones

A general protocol for the synthesis of a variety of functionalized quinazolinones has been developed through a sequential Pd-catalyzed coupling/1,5-alkyloxy/thio/azole shift/6π electrocyclization reaction of isocyanides and 2-carbonylaryl azides. When 3-(2-isocyanoethyl)indoles were utilized, an unusual competitive reaction between [1,5]-shift and indole-spirocyclization was observed, which renders a modular synthesis of quinazolinones and spiroindolenine-3,3'-pyrrolo[2,1-b]quinazolinones in a highly chemoselective manner.

Divergent Synthesis of Chromenoindoles and Spiroindolines via Domino Reaction of Indolyl-Substituted Isocyanides with Quinone Esters

A dearomative spirocyclization of tryptamine-derived isocyanides with quinone esters is developed for the divergent synthesis of structurally complex chromeno[2,3-b]indole and polycyclic spiroindoline scaffolds. This domino reaction features the formation and conversion of the six-membered dihydropyran ring with an amendable N,O-aminal moiety.

Diastereodivergent synthesis of chromeno[2,3-b]chromenes by tuning all of the reactivity centers of isocyanoacetate

A novel diastereodivergent tricyclization of isocyanoacetates with o-quinone methides was accomplished for the efficient synthesis of chromeno[2,3-b]chromene derivatives. All three reactive centers of isocyanoacetate reacted sequentially with two o-QMs, affording the products with four adjacent stereocenters in a diastereoselective manner. The asymmetric version was preliminarily investigated.

I2-Mediated [3 + 2] annulation of methyl-azaarenes with alkyl 2-isocyanoacetates or amino acid ester hydrochlorides: selective synthesis of iodine-functionalized and non-iodine-functionalized fused imidazoles

An I2-mediated [3 + 2] annulation of methyl-azaarenes with alkyl 2-isocyanoacetates or amino acid ester hydrochlorides has been demonstrated. This strategy involves the C≡N cleavage of isocyanides and can selectively...