A rapid growth in synthetic methods for the preparation of diverse organic molecules using N-sulfonyl-1,2,3-triazoles is of great interest in organic synthesis. Transition metals are generally used to activate the α-imino diazo intermediates. Metal-free methods have not been studied in detail, but can be a good complement to transition metal catalysis in the mild reaction conditions. We herein report a novel method for the preparation of 2,3-dihydroquinolin-4-imine and chroman-4-imine analogs from their corresponding N-sulfonyl-1,2,3-triazoles in the absence of metal catalysts. To achieve intramolecular annulation, the introduction of an electron-donating group is required at the meta position of N-sulfonyl-1,2,3-triazole methyl anilines. The inclusion of tailored substituents on the aniline moieties and nitrogen atoms enhances the nucleophilicity of the phenyl π-electrons, thus allowing them to undergo a Friedel-Crafts-type reaction with the highly electrophilic ketenimines. This metal-free method was carefully optimized to generate a variety of dihydroquinolin-4-imines and chroman-4-imines in moderate-to-good yields.
In this study, a series of variously substituted 2,3-dihydroquinolin-4-imines (DQIs) were synthesized from N-substituted propargylanilines by copper(I)-catalyzed annulation. The approach adopted in this study under mild, effective conditions exhibited broad substrate tolerance, particularly for functional groups substituted on anilines. Most of the DQI derivatives synthesized under optimal conditions were obtained in good isolated yields of 63-88 %. 2,3-Dihydroquinolinimine thus obtained was easily converted to important structures like 2,3-dihydroquinolone and tetrahydrobenzodiazepin-5-one, confirming the importance of this strategy in constructing various heterocycles. Surprisingly, 2,3-dihydroquinolinimines thus obtained exhibited bright fluorescence with quantum yields up to 66 %. The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed for understanding the excited-state nature of DQI system. Accordingly, a tailored DQI derivative bearing methoxy group at C-6 position and acetoxy group at C-7 position was designed and synthesized to give emission at 559 nm with redshift compared to the 7-methoxy substituted DQI. A detailed study of DQI structures with their photophysical properties was performed with five control molecules and consequently demonstrated the uniqueness of the chemical structures of DQIs.
Breast cancer (BC) is one of the most common malignancies
in the
world with aberrantly expressed glycans. The different types and stages
still limit a comprehensive method in the prediagnosis of BC patients.
In this research, a synthetic boronic acid-disulfide (BASS) probe
has been developed for the two steps of O → S → N acyl
transfer in glycoprotein recognition and labeling. The specificity
and sensitivity of this method have been carefully studied in the
case of immunoglobulin G, and the labeling efficiency was determined
up to 60%. The BASS-functionalized slide is a powerful platform for
monitoring the alteration of glycan patterns in human sera. Compared
to the samples from healthy individuals, sera of BC patients gave
specific patterns to eight lectins binding. The BASS-directed glycoprotein
strategy promises a rapid sensing platform for a high-throughput screening
of clinical BC samples and could be easily applied to other cancer
prediagnoses.
Thermally Induced Denitrogenative Annulation for the Synthesis of Dihydroquinolinimines and Chroman-4-imines. -Various aniline and phenol derivatives bearing an N-tosyl-1,2,3-triazole side chain are investigated with a view to preparing the title heterocycles under metal-free conditions at an elevated temperature. An electron-donating group is required at the meta position of the aryl moieties; no reaction is observed if ortho or para substituents are present. The tosylimine function in the products can be further elaborated as is demonstrated for derivative (IVb). -(CHOU, C.-H.; CHEN, Y.-Y.; RAJAGOPAL, B.; TU, H.-C.; CHEN, K.-L.; WANG, S.-F.; LIANG, C.-F.; TYAN, Y.-C.; LIN*, P.-C.; Chem. -Asian J. 11 (2016) 5, 757-765, http://dx.
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