Rh(III)-Catalyzed Chemoselective [4 + 2] Annulations for the Synthesis of [1,3]Oxazinoindolones: A Combined Experimental and Computational Study.

The interaction of -alkoxy-1-indole-1-carboxamides with transition metals leads to indole-fused heterocyclic scaffolds through directing group leaving/migration, [3 + 2], N-C2 [4 + 1], and [4 + 2] annulations. However, the corresponding O-C2 [4 + 2] annulation reactions have never been reported. Herein, we report the chemoselective annulation of -alkoxy-1-indole-1-carboxamides catalyzed by Rh(III), affording [1,3]oxazinoindolones through a hitherto unknown reaction pathway.

Gold(I)-Catalyzed Regioselective Synthesis of Indenylidene Derivatives via 1,5-Acryl Migration.

A novel gold (I)-catalyzed synthetic strategy has been achieved for an efficient construction of indenylidene derivatives from substituted 1,6-diynes. This reaction describes the unique reactivity of gold catalysis in facilitating the intramolecular [3,3]-sigmatropic rearrangement, 5-exo dig cyclization followed by 1,5-migration of acryl group, resulting in the formation of substituted indenylidenes. Various substituted indenylidenes were successfully synthesized with up to 92 % yields.

Dual gold-catalyzed regioselective synthesis of benzofulvenes 5- cyclization.

An efficient dual gold-catalyzed regioselective synthesis of benzofulvenes has been developed from substituted allyloxy 1,5-diynes 5- cyclization. In this intramolecular organic transformation a new C-C bond formation occurs and moderate to very good yields are obtained in one pot.

Silver-catalyzed Regioselective Synthesis of N-aryl-1H-pyrazolyl-substituted Benzenesulfonamides from Ynamides and Pyrazoles.

Silver-catalyzed N-aryl-1H-pyrazolyl substituted benzenesulfonamide derivatives were obtained regioselectively from ynamides and pyrazoles. In this intermolecular organic transformation, several substituted benzenesulfonamides were obtained in good to excellent yields by forming a new C-N bond under mild reaction conditions.

Synthesis of Isoquinoline-Derived Diene Esters and Quinolin-2(1)-ylidene-Substituted 1,5-Diones from Enynones and (Iso) Quinoline -Oxides.

An efficient synthetic method was developed to access isoquinoline-derived diene esters from enynones and isoquinoline--oxides in an atom-economic manner. The isoquinoline-substituted diene esters were obtained in moderate to excellent yields via [3 + 2]-cycloaddition and isoxazole ring opening followed by a [1,5]-sigmatropic rearrangement reaction, which resulted in one C-C and two C-O bond formations. Further, quinolin-2(1)-ylidene-substituted 1,5-diones were achieved by reaction of enynones with quinoline--oxides in very good to high yields.

Catalyst- and Additive-Free Methodical Ring Expansion Protocol to Access Benzooxepino-Fused Pyrroles.

An efficient metal-free, additive-free synthetic method was developed to access benzooxepino-fused pyrrole derivatives from alkynyl substituted aziridines. In this organic transformation, two new C-C bonds were formed via initial cleavage of C-C bond of aziridine ring by in situ generated azomethine ylides. Moderate to excellent yields of benzooxepino-fused pyrroles were obtained atom economically in the presence of t-BuOH in one-pot.

Gold(I)-Catalyzed Regioselective Cyclization to Access Cyclopropane-Fused Tetrahydrobenzochromenes.

Gold(I)-catalyzed efficient synthetic transformation was achieved to access the tetrahydrobenzo[]cyclopropa[]chromenes from allyl-substituted 1,6-diynes. Cyclopropane-fused tetrahydrobenzochromenes were obtained regioselectively in ≤92% yields. In this atom-economic organic transformation, three new C-C bonds were formed sequentially in one pot.

Copper(I)-Catalyzed Formation of Isoquinoline and Quinoline Substituted Isobenzofurans.

An efficient synthetic organic transformation was developed to access isoquinoline-substituted isobenzofurans by reaction of substituted 1,5-diynes with isoquinoline -oxides. Moderate to excellent yields of isoquinoline-derived isobenzofurans were achieved by formation of a new C-C and two C-O bonds in the presence of copper catalyst in one pot. whereas quinoline-substituted isobenzofurans were obtained when the reaction was conducted using quinoline -oxides and 1,5-diynes in the presence copper catalyst.

Cationic Gold-Catalyzed Intramolecular Cyclization of Substituted 1,5-Diynes to Access Indenone Derivatives.

An efficient intramolecular cyclization reaction was developed to achieve indenone derivatives. The substituted 1,5-diyenes were converted to the corresponding indenones via a gold-catalyzed organic transformation, and moderate to excellent yields of the title molecules were obtained via formation of two C=O and one C-C bonds under mild reaction conditions in one pot.

Gold (I)-Promoted Intermolecular Cascade Annulation to Access 2-Hydroxybenzocarbazoles via a Meyer-Schuster Rearrangement.

An efficient cascade annulation protocol was established to access substituted 2-hydroxybenzocarbazoles from alkynylcyclohexadienones and substituted 2-aminophenols under gold catalysis. In this transformation a new C-C, two C-N bonds were formed sequentially and moderate to excellent yields of 2-hydroxybenzocarbazole derivatives were obtained selectively via Meyer-Schuster rearrangement in one-pot.

Gold-catalyzed synthesis of 1-isochromene-4-carbaldehydes oxidative cascade cyclization.

An efficient gold-catalyzed formation of indenylidene-derived 1H-isochromene-4-carbaldehydes from substituted 1,5,10-triyne-O-silanes was developed under mild reaction conditions. In this reaction, gold-catalyzed selective oxidation, 1,2-migration, nucleophilic addition and then 5-endo-dig cyclization took place regioselectively. The indenylidene-derived isochromene-4-carbaldehydes were synthesized in moderate to very good yields via the formation of new C-C and C-O bonds in one pot.

Gold(iii) promoted formation of dihydroquinazolinones: double X-H activation by gold.

An efficient 2-furyl gold-carbene promoted synthetic method was developed for the formation of dihydroquinazolinones from enynones by dual insertion of anthranilamides. In this organic transformation a new C-O and two C-N bond formations occurred and dihydroquinazolinones were obtained with a quaternary centre in moderate to very good yields in one-pot synthesis.

Gold-Catalyzed Synthesis of 6-Hydroxyindoles from Alkynylcyclohexadienones and Substituted Amines.

An efficient gold-catalyzed formation of 6-hydroxyindoles from substituted alkynylcyclohexadienones and amines have been developed. In this reaction two new C-N bonds were formed, and moderate to very good yields of the 6-hydroxyindole derivatives were obtained in one pot. This organic transformation tolerates a range of substituted alkynylcyclohexadienones and amines, which resulted in 6-hydroxyindole derivatives selectively.

A gold-catalyzed facile intramolecular rearrangement and cyclization sequence for synthesis of 2,5-dihydrofurans.

An efficient gold-catalyzed intramolecular rearrangement and cyclization protocol was developed for synthesis of 2,5-dihydrofuran derivatives from O-propargyl β-enaminones. In this organic transformation new C-C and C-O bonds are formed under mild reaction conditions; this includes the formation of a quaternary centre.

Gold-carbene assisted formation of tetraarylmethane derivatives: double X-H activation by gold.

An efficient gold-carbene promoted generation of tetraarylmethane derivatives from enynones and indoles was accomplished by the formation of a new C-O bond and two C-C bonds. It is significant that (2-furyl) gold-carbene assisted addition of two nucleophiles resulted in the formation of tetraarylmethane derivatives with a quaternary centre in moderate to good yields in one pot.

Gold-catalyzed formation of aryl-fused pyrazolooxazepines via intramolecular regioselective 7-exo-dig cyclization.

An efficient method was developed for the synthesis of substituted aryl-fused pyrazolooxazepines from ortho-O-propargyl aryl pyrazoles by gold catalysis. In this organic transformation a new C-N bond was formed regioselectively via 7-exo-dig cyclization. Moderate to good yields of aryl-fused pyrazolooxazepine derivatives were obtained with significant molecular complexity in one-pot.

Synthesis of medium-sized aryl-fused nitrogenous heterocycles via sequential aryne aza-Claisen rearrangement/ring-closing metathesis.

The reaction of arynes and secondary allylamines furnished ortho-allyl-substituted N-arylanilines via an aza-Claisen rearrangement. In this transformation, the sequential formation of C-C and C-N bonds occurred by involving two aryne molecules under metal-free reaction conditions to provide moderate to good yields of the products. The obtained ortho-allyl-substituted N-arylaniline derivatives were further converted into aryl-fused medium-sized (7-9) nitrogenous heterocyclic molecules such as azepines, azocines and azonines via ring-closing metathesis (RCM).

Gold-catalyzed intramolecular cyclization/condensation sequence: synthesis of 1,2-dihydro[c][2,7]naphthyridines.

An efficient gold-catalyzed synthetic protocol for the construction of 1,2-dihydro[c][2,7]naphthyridines from 2-aminophenyl prop-2-yn-1-yl enaminones has been developed. In this organic transformation new C-C and C-N bond formations occur via 6-endo-dig cyclization and condensation. 1,2-Dihydro[c][2,7]naphthyridine derivatives were obtained in good to excellent yields in a one-pot synthesis at ambient temperature.

Gold-Catalyzed Intramolecular Regioselective 7-exo-dig Cyclization To Access 3-Methylene-3,4-dihydrobenzo[b]oxepinones.

An efficient gold-catalyzed synthesis of substituted 3-methylene-3,4-dihydrobenzo[b]oxepinones from ortho-O-propargyl substituted aryl enaminones has been achieved. In this transformation a new C-C bond formation occurred regioselectively via 7-exo-dig cyclization. Benzooxepinone derivatives were obtained in good to excellent yields in a one-pot synthesis at ambient temperature.

Gold(iii)-catalyzed synthesis of aroylbenzo[b]oxepin-3-ones from ortho-O-propargyl-1-one substituted arylaldehydes.

An efficient gold-catalyzed intramolecular cyclization of ortho-O-propargyl-1-one substituted arylaldehydes has been achieved for the generation of substituted aroylbenzo[b]oxepin-3-one derivatives in moderate to good yields. This synthetic transformation proceeds via gold-catalysed oxidation of the internal alkyne moiety followed by an intramolecular condensation leading to seven-membered oxacycles.

Gold-Catalyzed Intramolecular Cyclization of N-Propargylic β-Enaminones for the Synthesis of 1,4-Oxazepine Derivatives.

An efficient and mild one-pot, gold-catalyzed intramolecular cyclization of N-propargylic β-enaminones has been achieved for the generation of 1,4-oxazepine derivatives. This synthetic transformation tolerates a range of substituted N-propargylic β-enaminones in moderate to good yields.

Reaction of β-enaminones and acetylene dicarboxylates: synthesis of substituted 1,2-dihydropyridinones.

Synthesis of substituted 1,2-dihydropyridinones is described in a one pot reaction of β-enaminones and acetylene dicarboxylates where new C-C and C-N bonds were formed. The title compounds were obtained in moderate to good yields.

Gold-catalysed cyclisation of N-propargylic β-enaminones to form 3-methylene-1-pyrroline derivatives.

A gold(I) catalysed reaction between N-propargylic β-enaminones and arynes was developed to access 3-methylene-1-pyrrolines. The title compounds were obtained in 57-78% yields. This reaction is useful for the generation of substituted 1-pyrrolines exhibiting significant molecular complexity.

Effect of Nanospace Confinement on the Catalytic Activity and Stability of a Chiral Schiff Base Complex (CuL; L=C H N O ): A Combined Experimental and Theoretical Study.

Emerging trends in recyclable homogeneous chiral catalysts and their application in asymmetric synthesis are prompting a renewed interest in the field of catalysis as well as in industry. However, owing to fatal disadvantages of the homogeneous catalyst, they are not easily recoverable and recyclable. Herein, a comparison is made of the recyclability and stability of a homogeneous chiral Cu Schiff base complex of general formula CuL, in which L=C H N O , with that of a zeolite-Y-confined heterogeneous catalyst.

Enantioselective Henry reaction catalyzed by "ship in a bottle" complexes.

Two chiral Schiff-base complexes of copper(II) have been successfully encapsulated inside the cavity of zeolite-NaY via a "ship in a bottle" synthesis method. The presence of the two complexes inside the cages of zeolite-Y has been confirmed based on various spectrochemical and physicochemical techniques, viz. FTIR, UV-vis/DRS, ESR, XPS, CV, EDX, SEM, and TGA.