Zili Chen

Formal Intermolecular [2 + 2] Cycloaddition Reaction of Alleneamides with Alkenes via Gold Catalysis

An efficient method was developed to construct the densely functionalized cyclobutane[corrected] adducts through formal intermolecular cycloaddition of allenamides [corrected] with electron-rich olefins via gold catalysis, in which vinyl ethers/amides and electron-rich styrenes worked very well. In addition, a series of allenamide [corrected] dimerization products were prepared from the same allenamide [corrected] substrates.

Gold Catalyzed Diastereoselective Cascade Allylation/Enyne Cycloisomerization to Construct Densely Functionalized Oxygen Hetereocycles

A new tandem allylation/enyne cycloisomerization reaction was developed to construct densely functionalized oxygen heterocycles with high diastereoselectivities from the intermolecular reaction of allylic acetates with propargylic alcohols via gold catalysis. Terminal and nonterminal propargylic alcohols take different reaction routes either to provide 3-oxa-bicyclo[4.1.0]hept-4-ene derivatives 5 or to give endocyclic rearrangement products 7 and alkoxycyclization adducts 8. Cyclopropanes stereochemistry was mainly determined by allylic substituents.

Azepine Synthesis from Alkyl Azide and Propargylic Ester via Gold Catalysis

An efficient new method was developed to synthesize multisubstituted 4,5-dihydro-1H-azepine derivatives through the gold-catalyzed reaction of two molecules of propargylic esters with one molecule of alkyl azide. It was proposed that vinyl gold carbenoid, in situ generated from propargylic ester through gold-catalyzed 1,2-rearrangement, was trapped by alkyl azide to give vinyl imine intermediate. These, in turn, could undergo a formal [4 + 3] cycloaddition with another molecule of vinyl gold carbenoid to afford the desired azepine product.

Single-fluorophore-based fluorescent probes enable dual-channel detection of Ag+ and Hg2+ with high selectivity and sensitivity

A new type of fluorescent probe capable of detecting Ag(+) and Hg(2+) in two independent channels was developed in the present work. Specifically, in CH3CN-MOPS mixed solvents with CH3CN/MOPS ratio (v/v) of 15/85, this type of probe fluoresced weakly, and the addition of Ag(+) remarkably induced fluorescence enhancement of the probe. In CH3CN-MOPS mixed solvents with the percentage of CH3CN increased up to 65%, the probe was highly fluorescent and addition of Hg(2+) dramatically induced the fluorescence quenching. Thus, using such single-fluorophore-based probe and tuning the polarity of the mixed solvent, Ag(+), and Hg(2+) can be detected in independent channels with high selectivity and sensitivity. As a result, the mutual interference usually encountered in most cases of Ag(+) and Hg(2+) sensing owing to the similar fluorescence response that these two ions induced, can be effectively circumvented by using the probes developed herein.

Highly N2-selective coupling of 1,2,3-triazoles with indole and pyrrole.

Hydrogen-bond mediated coupling of 1,2,3-triazoles to indoles and pyrroles results in N2 selective functionalization of the triazole moiety in moderate to excellent yields. The reaction was tolerant of un-, mono- and disubstituted triazoles and was applied to synthesize tryptophan derived fluorescent amino acids.

N2-Selective Iodofunctionalization of Olefins with NH-1,2,3-Triazoles to provide N2-Alkyl-Substituted 1,2,3-Triazoles

A new method was developed to synthesize N(2)-alkyl-substituted 1,2,3-triazole through N-iodosuccinimide (NIS) mediated iodofuctionalization reaction of the alkene group with bi-, mono-, and unsubstituted NH-1,2,3-triazoles. The favored N-1 type hydrogen bond between the iodonium ion intermediate and 1,2,3-triazole was supposed to be generated, which gave the desired N(2)-alkyl triazole with a high N(2)-selectivity.

NHC-Ag(I)-Catalyzed Three-Component 1,3-Dipolar Cycloaddition To Provide Polysubstituted Dihydro-/Tetrahydrofurans

A new method was developed to synthesize polyfunctionalized dihydrofuran and tetrahydrofuran derivatives from the three-component [2 + 2 + 1] cycloaddition of the diazoesters with aryl/alkenyl aldehydes and alkyne/olefin dipolarophiles by using a Ag(I) N-heterocyclic carbene complex as the catalyst. A carbonyl ylide intermediate was generated, which undertook an endo-type 1,3-dipolar cycloaddition to provide the desired dihydro-/tetrahydrofurans in high regio- and diastereoselectivities by using α-aryl or α-alkenyl diazoesters.

Divergent synthetic routes for ring expansion or cyclization from 1,4-allylic diol derivatives via gold(I) catalysis or zinc(II) mediation.

A new efficient method was developed to transform cyclic alkanols into one-carbon higher homologated ketones using various esters as the leaving groups through gold-catalyzed allylic cation-promoted pinacol-type rearrangement. This reaction, coupled with oxy-Cope rearrangement, provided a new strategy to synthesize five-carbon homologated ring ketones. In addition, using ZnBr(2), 2,5-dihydrofuran products were obtained in moderate to good yields via an intramolecular cyclization process.

Gold Catalyzed Carbocyclization of Dienyl Acetates to Construct Mutifunctionalized 3-Vinyl Cyclohexanol Derivatives

A convenient new method was developed to construct six-membered 3-vinylcyclohexanols (and piperidine products) and 6-oxabicyclo[3.2.1]octan-7-one derivatives with high diastereoselectivities from 1,6-dienyl acetates via gold catalysis. The reaction proceeded through the nucleophilic addition of the alkenes onto the allylic cation group via a 6-endo-trig process. The substrates structure affected the configuration orientation of the allylic cation group in a boatlike transition state, which afforded either the trans-cyclohexanols or cis-piperidine derivatives.

Brönsted acid catalyzed addition of N 1 - p -methyl toluenesulfonyl triazole to olefins for the preparation of N 2 -alkyl 1,2,3-triazoles with high N 2 -selectivity

An efficient new method has been developed to synthesize N 2 -alkyl 1,2,3-triazole products by toluenesulfonic acid (TsOH) catalyzed addition of N 1 -Ts substituted 1,2,3-triazoles to olefins. The reactions of monosubstituted and unsubstituted triazole substrates with various olefins, including vinyl esters, are explored.