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20657-34-5

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20657-34-5 Usage

Check Digit Verification of cas no

The CAS Registry Mumber 20657-34-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,0,6,5 and 7 respectively; the second part has 2 digits, 3 and 4 respectively.
Calculate Digit Verification of CAS Registry Number 20657-34:
(7*2)+(6*0)+(5*6)+(4*5)+(3*7)+(2*3)+(1*4)=95
95 % 10 = 5
So 20657-34-5 is a valid CAS Registry Number.

20657-34-5Relevant articles and documents

Efficient preparation method of symmetric diarylethene compound

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Paragraph 0059-0061, (2021/02/10)

The invention belongs to the technical field of fine chemicals and related chemistry, and provides an efficient preparation method of a symmetric diarylethene compound. The method comprises the following steps: with halomethyl-containing aromatic hydrocarbon and derivatives thereof as raw materials, conducting reacting at 100 DEG C for 12 hours in the presence of a catalyst, alkali, additives andan anhydrous organic solvent so as to obtain the corresponding diarylethene compound with symmetry. The method has the beneficial effects that no transition metal reaction exists, reaction conditionsare mild, operation is simple and convenient, the possibility of industrialization is realized, and the diarylethene compound is obtained at high yield; and the diarylethene compound synthesized by using the method can be further functionalized to obtain various compounds, and is applied to development and research of natural products, functional materials and fine chemicals.

Selenenate Anions (PhSeO?) as Organocatalyst: Synthesis of trans-Stilbenes and a PPV Derivative

Zheng, Zhipeng,Trofymchuk, Oleksandra S.,Kurogi, Takashi,Varela, Elena,Mindiola, Daniel J.,Walsh, Patrick J.

supporting information, p. 659 - 666 (2020/01/02)

The selenenate anion (RSeO?) is introduced as an active organocatalyst for the dehydrohalogen coupling of benzyl halides to form trans-stilbenes. It is shown that RSeO? is a more reactive catalyst than the previously reported sulfur analogues (sulfenate anion, RSO?) and selenolate anions (RSe?) in the aforementioned reaction. This catalytic system was also applied to the benzylic-chloromethyl-coupling polymerization (BCCP) of a bis-chloromethyl arene to form ppv (poly(p-phenylene vinylene))-type polymers with high yields, Mn (average molecular weight) up to 13,000 and ? (dispersity) of 1.15. (Figure presented.).

Photoinitiated carbonyl-metathesis: Deoxygenative reductive olefination of aromatic aldehydes: Via photoredox catalysis

Wang, Shun,Lokesh, Nanjundappa,Hioe, Johnny,Gschwind, Ruth M.,K?nig, Burkhard

, p. 4580 - 4587 (2019/05/14)

Carbonyl-carbonyl olefination, known as McMurry reaction, represents a powerful strategy for the construction of olefins. However, catalytic variants that directly couple two carbonyl groups in a single reaction are less explored. Here, we report a photoredox-catalysis that uses B2pin2 as terminal reductant and oxygen trap allowing for deoxygenative olefination of aromatic aldehydes under mild conditions. This strategy provides access to a diverse range of symmetrical and unsymmetrical alkenes with moderate to high yield (up to 83%) and functional-group tolerance. To follow the reaction pathway, a series of experiments were conducted including radical inhibition, deuterium labelling, fluorescence quenching and cyclic voltammetry. Furthermore, NMR studies and DFT calculations were combined to detect and analyze three active intermediates: a cyclic three-membered anionic species, an α-oxyboryl carbanion and a 1,1-benzyldiboronate ester. Based on these results, we propose a mechanism for the CC bond generation involving a sequential radical borylation, "bora-Brook" rearrangement, B2pin2-mediated deoxygenation and a boron-Wittig process.

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