Xinwei He

FeCl3-Catalyzed Four-Component Nucleophilic Addition/Intermolecular Cyclization Yielding Polysubstituted Pyridine Derivatives

We report an efficient route to pyridine derivatives via an FeCl3-catalyzed four-component nucleophilic addition/intermolecular cyclization. This simple fragment assembly strategy uses mild conditions and affords a broad range of polysubstituted pyridines in moderate to good yield from simple and readily available starting materials. A plausible mechanism for this process is proposed.

Synthesis of Isocoumarins from Cyclic 2-Diazo-1,3-diketones and Benzoic Acids via Rh(III)-Catalyzed C–H Activation and Esterification

A mild and efficient Rh(III)-catalyzed C-H activation/esterification reaction for the synthesis of isocoumarins has been developed. This procedure uses readily available benzoic acids and cyclic diazo-1,3-diketones as starting materials and involves domino intermolecular C-H activation in combination with intramolecular esterification to give the corresponding isocoumarins in moderate to excellent yields. This process provides a facile approach for the construction of isocoumarins containing various functional groups that does not require any additives.

FeCl3-Mediated One-Pot Domino Reactions for the Synthesis of 9-Aryl/9-Arylethynyl-2,3,4,9-tetrahydro-1H-xanthen-1-ones from Propargylic Amines/Diaryl Amines and 1,3-Cyclohexanediones

An efficient, environmentally friendly and one-pot route to new 9-aryl/9-arylethynyl-2,3,4,9-tetrahydro-1H-xanthen-1-one derivatives from inexpensive starting materials has been developed. This method proceeded by a domino nucleophilic-substitution/intramolecular cyclization/dehydration sequence of propargylic amines/diaryl amines and 1,3-cyclohexanediones under the promotion of FeCl3, which involved the formation of two new σ (C-C and C-O) bonds in a single operation for the construction of novel tetrahydroxanthene skeletons in 68-95% yields.

FeCl3-Mediated Synthesis of β-Alkynyl Ketones via Domino Nucleophilic-Substitution/Intramolecular-Cyclization/Reverse Claisen Condensation of N-Cyclohexyl Propargylamines and 1,3-Diketones

The synthesis of β-alkynyl ketones was achieved in good to excellent yields by an iron-catalyzed domino reaction of N-cyclohexyl propargylamines and 1,3-diketones. A plausible mechanism involving nucleophilic substitution, intramolecular cyclization, and reverse Claisen condensation for this process is proposed.

Rh(III)-Catalyzed C–H Activation/Intramolecular Cyclization: Access to N-Acyl-2,3-dihydro-1H-carbazol-4(9H)-ones from Cyclic 2-Diazo-1,3-diketones and N-Arylamides

A Rh(III)-catalyzed C–H activation/cyclization cascade reaction is described. The reaction involves cyclic 2-diazo-1,3-diketones and N-arylamides, and it proceeds via an intermolecular C–C bond formation and subsequent intramolecular C–N bond formation. A variety of N-acyl-2,3-dihydro-1H-carbazol-4(9H)-ones were obtained under mild conditions in good to excellent yields (65–90%). Key features of this strategy include high-efficiency, operational simplicity, scalability, and broad functional-group tolerance. In addition, H2O and N2 are the only byproducts. Carbazole derivatives with free NH groups can be easily obtained through N-deprotection reactions.

Combinatorial synthesis of spiro[indoline-3,2′-pyrrole] derivatives via a three-component reaction under catalyst-free conditions

Reported here is a convenient catalyst-free method for preparing a series of spiro[indoline-3,2′-pyrroles] from a three-component reaction of isatins, α-amino acid and phenylpropiolic acid esters in refluxing isopropanol with high regioselectivity and yields. A plausible mechanism for this process was proposed. In addition, this protocol permitted the facile construction of spiro[indoline-3,2′-pyrroles] through an expanded scope of substrates.

Divergent synthesis of 3,4-dihydrodibenzo[b,d]furan-1(2H)-ones and isocoumarins via additive-controlled chemoselective C–C or C–N bond cleavage

Rh(III)-Catalyzed C–C/C–O bond formation between cyclic 2-diazo-1,3-diketones and salicylamides with additive-controlled chemoselectivity is described. The reaction proceeded under mild reaction conditions and exhibited good functional group tolerance and scalability. 3,4-Dihydrodibenzo[b,d]furan-1(2H)-ones were obtained in moderate to excellent yields (55–90%) through a tandem N–H activation/C–C cleavage/etherification process when AgNTf2 was used as the additive, whereas utilizing Cu(OAc)2 afforded isocoumarins in good yields (60–86%) via a C–H activation/C–N cleavage/lactonization pathway.

Selective Synthesis of Aminoisoquinolines via Rh(III)-catalyzed C-H/N-H Bond Functionalization of N-Aryl Amidines with Cyclic 2-Diazo-1,3-diketones

A simple C-H/N-H bond functionalization of N-aryl amidines with cyclic 2-diazo-1,3-diketones for the synthesis of 1-aminoisoquinolines has been accomplished by employing [Cp*RhCl2]2/CsOPiv as the catalyst system. This methodology proceeds by a cascade C-H activation/intramolecular cyclization under mild reaction conditions, features a broad substrate scope, and involves the formation of two new σ bonds (C-C and C-N) in a single operation for the construction of novel 1-aminoisoquinoline skeletons in good to excellent yields.