Efficient One-Pot Synthesis of Dibenzopyranones via a Decarboxylative Cross-Coupling and Lactonization Sequence

Construction of Six-Membered Lactam and Lactone Structures via Ligand-Free Pd-Catalyzed C-H Activation/[5 + 1] Cyclization Carbonylation

An approach for the ligand-free Pd-catalyzed C-H activation/[5 + 1] cyclization carbonylation by employing readily available ClCF2COONa as a carbonyl source via difluorocarbene transfer and hydrolysis has been developed. The current protocol enables us to obtain a series of carbonylation cyclization product benzopyranone and phenanthridinone derivatives in up to 91% yield with excellent functional group compatibility. This protocol has the advantages of mild reaction conditions, wide applicable substrates, and simple and safe operation and provides a new method for the synthesis of complex lactam and lactone compounds.

Cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids

The first cerium photocatalyzed dehydrogenative lactonization of 2-arylbenzoic acids has been developed. This operationally simple protocol allows rapid access to synthetically useful coumarins on gram scale by employing CeCl₃ as a photocatalyst and O₂ as a terminal oxidant. Overall, this delivers an economical and environmentally amiable entry to diversely substituted coumarins, important structural motifs in bioactive molecules.

Rh(III)-Catalyzed Annulation of Boc-Protected Benzamides with Diazo Compounds: Approach to Isocoumarins

A mild rhodium-catalyzed annulation of Boc-protected benzamides with diazo compounds via C−C/C−O bond formation has been explored. In the presence of [Cp*RhCl₂]₂, AgSbF₆ and Cs₂CO₃, Boc-protected benzamides can be effectively annulated to yield isocoumarins in 0.5–2 h.

Syntheses of Benzo[c]Chromen-6-ones by Palladium Catalyzed C–H Bond Activation using Diazonium Salts

An efficient palladium catalyzed C-H bond activation for the synthesis of benzo[ c]chromen-6-ones using diazonium salts is described. In the presence of Pd(OAc)2, dppp, PivOH and K2CO3, the diazonium salt can be transformed into the product through a denitrogenation/C-H bond activation/cyclization sequence in acetonitrile. Altogether, nine structurally diverse substituted benzo[ c]chromen-6-ones were prepared in excellent yields through two different methods.

A metal-free one-pot synthesis of benzo[c]chromen-6-ones from 3,4-dichlorocoumarins and butadienes using tandem photo-thermal-photo reactions

An efficient, simple and versatile synthesis of biologically valuable benzo[c]chromen-6-ones is achieved using a tandem photo-thermal-photo reaction sequence starting from 3,4-dichlorocoumarins and a 1,3-butadiene. In this concise one-pot protocol, neither metal catalyst nor peroxide promoter is needed and the products can be purified through simple recrystallization in most cases. The synthesis consists of a reaction sequence of photo-induced [4 + 2] and [2 + 2] cycloadditions, silica gel promoted elimination of HCl and electrocyclic cyclobutene ring opening followed by a photo-induced 6π electrocyclization. The reactions proceed well with a range of dichlorocoumarins and some typical butadienes to provide the corresponding annulated products in 70-80% yield.

[N,P]-pyrrole PdCl2complexes catalyzed the formation of dibenzo-α-pyrone and lactam analogues

Catalytic applications on direct intramolecular arylation was developed using a new family of palladium complexes that includes [N,P] ligands based on the pyrrole ring with α-phosphine and phosphole units.

Copper catalyzed room temperature lactonization of aromatic C–H bond: a novel and efficient approach for the synthesis of dibenzopyranones

A novel and efficient methodology has been developed for the intramolecular aryl C–H oxidative lactonization of 2-arylbenzaldehyde using a low-cost CuCl catalyst and TBHP as the oxidant at room temperature.

KOtBu mediated efficient approach for the synthesis of fused heterocycles via intramolecular O-/N-arylations

KO^tBu mediated an efficient methodology has been developed for the synthesis of 6H-benzo[c]chromenes, 6H-benzo[c]chromen-6-ones, carbazoles, dibenzofurans and dibenzooxepins.

Rh(iii)-catalyzed C–H activation/cyclization of benzamides and diazo compounds to form isocoumarins and α-pyrones

Rhodium-catalyzed intermolecular cyclization of benzamides and diazo compounds via C–H activation has been achieved to construct C–C/C–O bonds for the first time.

One-pot cascade reactions of 1-arylpenta-3,4-dien-2-ones leading to 2-arylphenols and dibenzopyroanones

A one-pot tandem reaction of 1-arylpenta-3,4-dien-2-ones with activated ketones allowed for an efficient synthesis of 2-arylphenols. Moreover, this reaction was found to be also compatible and combinable with Pd-catalyzed C–H activation and carbonylation of the in situ formed 2-arylphenols to provide dibenzopyranones.

An advanced and novel one-pot synthetic method for diverse benzo[c]chromen-6-ones by transition-metal free mild base-promoted domino reactions of substituted 2-hydroxychalcones with β-ketoesters and its application to polysubstituted terphenyls

Novel one-pot syntheses of a variety of benzo[c]chromen-6-one derivatives were accomplished by Cs₂CO₃-promoted reactions of 2-hydroxychalcones.

From π-expanded coumarins to π-expanded pentacenes

Dihydroxyanthraquinone can be transformed into head-to-tail bis-coumarins which undergo photo-dehydrogenative coupling leading to coronene derivatives.

Cu-catalyzed mild C(sp2)-H functionalization assisted by carboxylic acids en route to hydroxylated arenes

A formal Cu-catalyzed C(sp(2))-H hydroxylation assisted by benzoic acids is described. The procedure is characterized by its mild reaction conditions and wide substrate scope utilizing simple and cheap Cu catalysts, thus becoming a user-friendly and operationally simple protocol for C(sp(2))-H hydroxylation.