Synthesis of Benzofuro[3,2-]indol-3-one Derivatives via Dearomative (3 + 2) Cycloaddition of 2-Nitrobenzofurans and -Quinamines.

An efficient dearomative (3 + 2) cycloaddition of -quinamines and 2-nitrobenzofurans has been developed. This reaction proceeds smoothly under mild conditions and affords a series of benzofuro[3,2-]indol-3-one derivatives in good to excellent yields (up to 98%) with perfect diastereoselectivities (all cases > 20:1 ). The scale-up synthesis and versatile derivatizations demonstrate the potential synthetic application of the protocol.

Cu-Catalyzed Direct Asymmetric Mannich Reaction of 2-Alkylazaarenes and Isatin-Derived Ketimines.

The first direct catalytic asymmetric Mannich reaction of 2-alkylazaarenes and ketimines was realized with a chiral Cu-bis(oxazoline) complex as the catalyst. The asymmetric addition of 2-alkylpyridines to isatin-derived ketimines proceeded smoothly to afford α,β-functionalized 2-substituted pyridines bearing 3-amino-3,3-disubstituted oxindole motifs with excellent results (≤99% yield, 99:1 dr, and 98% ee). The catalytic system was also extended to 2-alkylbenzothiazoles as nucleophiles for the asymmetric Mannich reaction of ketimines.

A New Reaction Mode of 3-Halooxindoles: Acting as C-C-O Three-Atom Components for (3+3) Cycloaddition to Access Indolenine-Fused 2-1,4-Oxathiines.

Herein, we report an unprecedented implementation of 3-halooxindoles as C-C-O three-atom components for (3+3) cycloaddition with pyridinium 1,4-zwitterionic thiolates, affording structurally diverse indolenine-fused 2-1,4-oxathiines in moderate to high yields. A combined experimental and computational mechanistic study suggests that the reaction proceeds through addition of a S conjugate to the -azaxylylene intermediate, followed by O-Michael addition and a sequential retro-Michael addition/pyridine extrusion pathway.

Recent advances in copper-catalyzed decarboxylative reactions of propargylic cyclic carbonates/carbamates.

Copper-catalyzed decarboxylative reactions of propargylic cyclic carbonates/carbamates enable the efficient construction of widely available skeletons such as allenes, ethynyl-containing heterocycles, and tetrasubstituted stereogenic carbon centers. As an emerging field, these strategies have gained great attention and shown significant progress due to the presence of multiple electrophilic and nucleophilic reaction sites of propargylic cyclic carbonates/carbamates, as well as the distinct advantages of copper catalysis such as higher selectivity, low cost, and mild reaction conditions. In this review, the achievements in copper-catalyzed decarboxylative reactions of propargylic cyclic carbonates/carbamates are addressed.

Recent Progress in Heterocycle Synthesis: Cyclization Reaction with Pyridinium and Quinolinium 1,4-Zwitterions.

Heteroarene 1, n-zwitterions are powerful and versatile building blocks in the construction of heterocycles and have received increasing attention in recent years. In particular, pyridinium and quinolinium 1,4-zwitterions have been widely studied and used in a variety of cyclization reactions due to their air stability, ease of use, and high efficiency. Sulfur- and nitrogen-based pyridinium and quinolinium 1,4-zwitterions, types of emerging heteroatom-containing synthons, have attracted much attention from chemists.

Copper-Catalyzed Diastereo- and Enantioselective Decarboxylative [3 + 2] Cyclization of Alkyne-Substituted Cyclic Carbamates with Azlactones: Access to γ-Butyrolactams Bearing Two Vicinal Tetrasubstituted Carbon Stereocenters.

A copper-catalyzed diastereo- and enantioselective decarboxylative [3 + 2] cyclization reaction of alkyne-substituted cyclic carbamates with azlactones has been established. A range of optically pure γ-butyrolactams bearing two vicinal tetrasubstituted carbon stereocenters were obtained in high yields with good to excellent stereoselectivities (up to 99% yield, 99:1 dr, and 99% ee). This is the first example of asymmetric synthesis γ-butyrolactams containing sterically congested vicinal tetrasubstituted stereocenters via a decarboxylative cyclization pathway.

A new aromatic probe - The ring stretching vibration Raman spectroscopy frequency.

A new aromatic criterion is presented to determine the aromatic degree of the high symmetric molecules. Group theory is used to explain the correlation between the aromatic degree and the value of Ring Stretching Vibration Raman Spectroscopic Frequency (RSVRSF). The calculations of the geometrical optimization, nucleus-independent chemical shifts (NICS) and values of the Raman Spectroscopy for the aromatic molecules-LnHn (L=C, Si, Ge, n=3, 5-8) were performed using the Density Functional Theory (DFT) Method, as well as the correlations between the values of their RSVRSF and NICS values by Statistic Package for Social Science (SPSS17.