One‐Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)‐Catalyzed Multiple CH Activation and Annulation

A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C? H bond cleavage and C? C and C? N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C? H activation, alkyne insertion, and reductive elimination, is proposed for this transformation.     

Rhodium(III)‐Catalyzed Selective ortho‐Olefinations of N‐Acyl and N‐Aroyl Sulfoximines by CH Bond Activation

Two new rhodium‐catalyzed oxidative couplings between sulfoximine derivatives and alkenes by regioselective C?H activation, affording ortho‐olefinated (Heck‐type) products, are reported. A synthetic application of the ortho‐alkenylated products into the corresponding cyclic derivatives has been demonstrated, and a mechanistic rational for the rhodium catalysis is presented.     

Ru(II)-catalyzed C-H bond activation for the synthesis of substituted isoquinolinium salts from benzaldehydes, amines, and alkynes

An efficient method for the synthesis of substituted isoquinolinium salts from benzaldehydes, amines, and alkynes via ruthenium-catalyzed C-H bond activation and annulation in one pot is described.     

Native Fluorescence and Time Resolved Fluorescence Spectroscopic Characterization of Normal and Malignant Oral Tissues Under UV Excitation—an In Vitro Study

The present work aims to investigates the native fluorescence and time resolved fluorescence spectroscopic characterization of oral tissues under UV excitation. The fluorescence emission spectra of oral tissues at 280 nm excitation were obtained. From the spectra, it was observed that the alteration in the biochemical and morphological changes present in tissues. Subsequently, the Full width at Half Maximum (FWHM) of every individual spectra of 20 normal and 40 malignant subjects were calculated. The student’s t-test analysis reveals that the data were statistically significant (p?=?0.001). The fluorescence excitation spectra at 350 nm emission of malignant tissues confirms the alteration in protein fluorescence with respect to normal counterpart. To quantify the observed spectral differences, the two ratio variables R₁?=?I₂₇₅/I₃₁₀ and R₂?=?I₃₁₀/I₃₂₈ were introduced in the excitation spectra. Among them, the Linear Discriminant Analysis (LDA) of R₁ reveals better classification with 86.4 % specificity and 82.5 % sensitivity. The fluorescence decay kinetics of oral tissues was obtained at 350 nm emission and it was found that the decay kinetics was triple exponential. Then the ROC analysis of fractional amplitudes and component lifetime reveals that the average lifetime shows 77 % sensitivity and 70 % specificity with the cut off value 4.85 ns. Briefly, the average lifetime exhibits better statistical significance when compared to fractional amplitudes and component lifetimes.     

Hydroarylations of Heterobicyclic Alkenes through Rhodium‐Catalyzed Directed CH Functionalizations of S‐Aryl Sulfoximines

Rhodium‐catalyzed directed CH‐functionalizations have been used in hydroarylations of heterobicyclic alkenes with NH‐sulfoximines. Unexpectedly, the bicyclic framework is retained, resulting in the formation of addition products being attractive intermediates for functionalized molecules that are difficult to prepare by other means.     

RhIII‐Catalyzed C?H Activation: A Versatile Route towards Various Polycyclic Pyridinium Salts

An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2‐aryl‐pyridines and 2‐aryl‐sp²‐nitrogen‐atom‐containing heterocycles with alkynes through rhodium(III)‐catalyzed C? H activation and annulation under an O₂ atmosphere is described. A possible mechanism that involves the chelation‐assisted C? H activation of the 2‐aryl‐pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five‐membered rhodacycle ( I′ ). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.