A non-noble metal-free protocol has been developed for C−H bond functionalization at room temperature by merging cobalt-mediated catalysis with photocatalysis. The reaction requires only oxygen as sole oxidant and operated at room temperature under redox-neutral conditions. Visible-light activated photoredox catalyst functions as an electron transfer reagent with oxygen as a terminal oxidant in the cobalt-mediated C−H and N−H bond annulation. The developed methodology allows annulations with various coupling partners. The concept demonstrated herein is expected to enhance the scope of cobalt catalysis as applied to sustainable fine chemical synthesis.
This Graphical Review provides a concise overview of the manifold and mechanistically diverse methods that enable the functionalization of sp3 C–H bonds in amines and their derivatives.
A simple
one-pot procedure enables the sequential, regioselective,
and diastereoselective introduction of the same or two different substituents
to the α- and α′-positions of unprotected azacycles.
Aryl, alkyl, and alkenyl substituents are introduced via their corresponding
organolithium compounds. The scope of this transformation includes
pyrrolidines, piperidines, azepanes, and piperazines.
Secondary alicyclic amines are converted to their corresponding ring-fused imidazoles in a simple procedure consisting of oxidative imine formation followed by a van Leusen reaction. Amines with an existing α-substituent undergo regioselective ring-fusion at the α'-position. This method was utilized in a synthesis of fadrozole.
Raspberry Pi is employed as a basic embedded system and being a low cost single-board computer, it has emerged to be immensely popular in recent times. This paper mainly deals with natural color of an image including human faces in HSI color space. In this kind of image, it is necessary to describe skin color accurately hence we go on to restore the image based on this criterion. Histogram equalization (HE) is a popular technique for contrast enhancement of images. In order to vary the enhancement degree to get proper skin color, HE with variable enhancement degree (HE-VED) is introduced. The enhancement degree of HE-V ED is controlled by intensity and saturation parameter II and JI respectively. Dark and low contrast images were captured using the Raspberry Pi camera module and HE-VED was applied to enhance the objective image in a particular enhancement degree automatically with help of Raspberry Pi. Lastly HE-VED was extended to a complete image and appreciable results were obtained which could be further enhanced using different pseudo coloring techniques. Index Terms-Histogram equalization, HSI color space, Python image library, Raspberry Pi, Raspbian wheezy, skin color.
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