Dibrominated Addition and Substitution of Alkenes Catalyzed by Mn2(CO)10

2021 ◽  
Author(s):  
Xianheng Song ◽  
Shanshui Meng ◽  
Hong Zhang ◽  
Yi Jiang ◽  
Albert S. C. Chan ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Practical Method ◽  
Molecular Bromine

A practical method for dibromination of alkenes without using molecular bromine is consistently appealing in organic synthesis. Herein we report a Mn-catalyzed dibrominated addition and substitution of alkenes only with...

CsF in Organic Synthesis. A Practical Method for Inversion of Secondary Mesylates

Synlett ◽  
1995 ◽  
Vol 1995 (04) ◽  
pp. 336-338 ◽  
Author(s):  
Tsuneo Sato ◽  
Junzo Otera
Keyword(s):  
Organic Synthesis ◽  
Practical Method

An Efficient and Green Procedure for the Synthesis of Quinoxaline Derivatives using 3,5-Bis(trifluoromethyl)phenylammonium triflate (BFPAT) Organocatalyst

2020 ◽  
Vol 17 ◽  
Author(s):  
Samad Khaksar ◽  
Mandana Alipour ◽  
Zinatosadat Hossaini ◽  
Faramarz Rostami-Charati
Keyword(s):  
Organic Synthesis ◽  
Toxic Metals ◽  
Water Solution ◽  
Reaction Medium ◽  
Practical Method ◽  
Green Solvent ◽  
Efficient Synthesis ◽  
Organic Transformations ◽  
Quinoxaline Derivatives ◽  
Green Procedure

Aims: Aims:The application of 3,5-Bis(trifluoromethyl) phenyl ammonium triflate(BFPAT) as a convenient and novel organocatalyst for the synthesis of quinoxalines. Background: Recently, ammonium triflate-based organocatalysts have been rapidly evolved, and most of them have been synthesized and utilized in several organic transformations. Objective: 1) introducing a new organocatalyst 2) introducing a practical method for the synthesis of quinoxalines 3) to overcome some problem in this method 4) using water as a green solvent. Method: A water solution (3 ml) of 1,2-dicarbonyl compounds (1 mmol) and aryl 1,2-diamines (1 mmol) was mixed with BFPAT (10 mol%), and the resulting mixture was stirred at rt for an appropriate time. Upon completion of the reaction, (monitored by TLC), the resultant was cooled with the ice bath, filtered and washed with ethanol and purified by recrystallization from hot ethanol to afford pure products. Result: A wide variety of quinoxaline derivatives was achieved by the reaction of various substituted o-phenylenediamines and 1,2-diketones in water. Conclusion: A simple and new ammonium triflate-based organocatalyst was shown to effectively promote the highly efficient synthesis of quinoxalines in water as a green reaction medium. Compared to prior studies, the substrate scope of the starting material was largely extended. In particular, the synthesis avoids the toxic metals in the products, which provides a green and practical method for organic synthesis. Other: In particular, the synthesis avoids the toxic metals in the products, which provides a green and practical method for organic synthesis.

scholarly journals Review for metal and organocatalysis of heterocyclic C-H functionalization

2021 ◽  
Vol 9 (1) ◽  
pp. 001-030
Author(s):  
Ahmed A. El-Sayed ◽  
Nahid Y. Khaireldin ◽  
Eman A. El-Hefny
Keyword(s):  
Organic Synthesis ◽  
Heterocyclic Compounds ◽  
Bond Activation ◽  
Practical Method ◽  
Metal Catalysis ◽  
Bond Functionalization ◽  
Heterocyclic Derivatives

Over the last few decades, significant efforts have been put forth towards the C−H bond group functionalization by transition-metalcatalysis and organocatalysis. Several efficient strategies to convert C-H bond to other groups C-C, C-N, C-O bonds have been implemented. The most attractive C-H bond functionalization was the C-H heterocyclic compounds activation that is practical method in organic synthesis. The new C–C, C–N and C–O bond as formed from the C-H bond activation by two diverse ways metal catalysis and/or organocatalysis. The most important is the synthesis of new bioactive heterocyclic compounds by easy and less expensive materials. In this review, we will cover most of the syntheses of heterocyclic derivatives by the functionalization of C-H bond in metal and organocatalytic reagents.

The role of differential phase contrast in electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 176-177
Author(s):  
E.M. Waddell ◽  
J.N. Chapman ◽  
R.P. Ferrier
Keyword(s):  
Phase Contrast ◽  
Practical Method ◽  
Position Vector ◽  
Differential Phase ◽  
Pure Phase ◽  
Differential Phase Contrast ◽  
The Difference ◽  
Image Position ◽  
First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

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