A short route to multiply substituted fluorenones

Chemoselective synthesis of isolated and fused fluorenones and their photophysical and antiviral properties

Metal-free substituent dependent synthesis of fluorescent fluorenones was reported.

Efficient three-component one-pot synthesis of steroidal polysubstituted anilines

An efficient and practical base-promoted cascade reaction has been developed to access steroidal polysubstituted anilines from simple precursors. The protocol reported herein achieved the formation of a benzene ring as well as three continuous C-C bonds in a single operation. The reaction mechanism was proposed on the basis of the key intermediate obtained. Besides, this method could be potentially employed for the synthesis of biphenyl compounds. The adjacent amine and nitrile groups existed in the final products have the potential for late stage functionalization, which would provide efficient access to steroidal compound collections with structural diversity and complexity.

Synthesis of Fluoren-9-ones and Ladder-Type Oligo-p-phenylene Cores via Pd-Catalyzed Carbonylative Multiple C-C Bond Formation

A new route to various substituted fluoren-9-ones has been developed via an efficient Pd-catalyzed carbonylative multiple C-C bond formation. Under a CO atmosphere, using commercially available aryl halides and arylboronic acids as substrates, this three-component reaction proceeded smoothly in moderate to excellent yields with good functional-group compatibility. The mechanistic investigations suggested a sequential process for the reaction that forms o-bromobiaryls in the first stage followed by a cyclocarbonylation reaction. This chemistry has been successfully extended to construct ladder-type oligo-p-phenylene cores.

Synthesis of fluorenones by using Pd(ii)/Mg–La mixed oxide catalyst

Palladium(ii)/magnesium–lanthanum mixed oxide (Pd(ii)/Mg–La mixed oxide) catalyst was used in the dehydrogenative cyclization of benzophenones to afford fluorenones.

A convenient strategy for the annulation of aryl scaffold to A/B-ring steroids under microwave irradiation

A facile strategy for the annulation of 2,6-dicyanoaniline moiety to steroidal A/B-ring is described from base catalyzed and microwave-promoted reaction of steroidal 3-keto-2-hydroxymethylenes with malononitrile in high yields. The generality of the reaction has been extended to non-steroidal cyclic and aliphatic ketohydroxylmethylenes.

Synthesis of a new heterocyclic system — Fluoreno[1,2-d]imidazol-10-one

Synthesis of various substituted fluoreno[1,2-d]imidazol-10-ones (5a–5g) has been accomplished by the cyclization of diazotized 1-substituted 4-benzoyl-5- aminobenzimidazoles (4a–4g). Compounds 4a–4g were prepared by reductive ring opening of 3H-imidazo[4′,5′:3,4]benzo[c]isoxazoles (3a–3g) with zinc dust in EtOH/NaOH solution.

Carbon-hydrogen bond functionalization approach for the synthesis of fluorenones and ortho-arylated benzonitriles

A sequence consisting of palladium-catalyzed benzamide ortho-arylation/reaction with (CF3CO)2O was developed allowing a convenient one-pot synthesis of ortho-arylated benzonitriles and fluorenone derivatives. The outcome of this transformation is dependent on the amide N-alkyl substituent. Dehydration of ortho-arylated N-cyclohexyl-benzamides by (CF3CO)2O results in efficient production of benzonitriles. In contrast, o-arylated N-propylbenzamides are converted to fluorenone derivatives.

Efficient synthesis of fluoren-9-ones by the palladium-catalyzed annulation of arynes by 2-haloarenecarboxaldehydes

Fluoren-9-ones and derivatives are readily prepared in good yields by the annulation of in situ generated arynes by 2-haloarenecarboxaldehydes in the presence of a palladium catalyst.

An aryl to imidoyl palladium migration process involving intramolecular C-H activation

Biologically interesting fluoren-9-one and xanthen-9-one derivatives have been prepared by a novel aryl to imidoyl palladium migration, followed by intramolecular arylation. The fluoren-9-one synthesis appears to involve both a palladium migration mechanism and a C-H activation process proceeding through an unprecedented organopalladium(IV) hydride intermediate. The results from deuterium labeling experiments are consistent with the proposed dual mechanism.

Directed Metalation Route to Ferroelectric Liquid Crystals with a Chiral Fluorenol Core: The Effect of Restricted Rotation on Polar Order

A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a-e) or chiral fluorenol (3a-e) core were synthesized using a combined directed ortho metalation-directed remote metalation strategy. The SmC phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C11 fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (Po) values of +106 and +183 nC/cm2, respectively, at 10 K below the SmA*-SmC* phase transition temperature. The difference in Po values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor one orientation of its transverse dipole moment along the polar axis, and to steric coupling of the core to the chiral 2-octyloxy side chain.

Synthesis of fluoren-9-ones by the palladium-catalyzed cyclocarbonylation of o-halobiaryls

The synthesis of various substituted fluoren-9-ones has been accomplished by the palladium-catalyzed cyclocarbonylation of o-halobiaryls. The cyclocarbonylation of 4'-substituted 2-iodobiphenyls produces very high yields of 2-substituted fluoren-9-ones bearing either electron-donating or electron-withdrawing substituents. 3'-Substituted 2-iodobiphenyls afford 3-substituted fluoren-9-ones in excellent yields with good regioselectivity. This chemistry has been successfully extended to polycyclic fluorenones and fluorenones containing fused isoquinoline, indole, pyrrole, thiophene, benzothiophene, and benzofuran rings.

Synthesis of fluoren-9-ones via palladium-catalyzed cyclocarbonylation of o-halobiaryls

The synthesis of various substituted fluoren-9-ones has been accomplished by a novel palladium-catalyzed cyclocarbonylation of o-halobiaryls. The cyclocarbonylation of 4'-substituted-2-iodobiphenyls produces very high yields of 2-substituted fluoren-9-ones bearing either electron-donating or electron-withdrawing substituents. 3'-Substituted 2-iodobiphenyls afford in excellent yields with good regioselectivity 3-substituted fluoren-9-ones. This chemistry has been successfully extended to polycyclic and heterocyclic fluorenones.