Microbial cyclosophoraose as a catalyst for the synthesis of diversified indolyl 4H-chromenes via one-pot three component reactions in water

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  Green Chem., 2016, Advance Article
  DOI: 10.1039/C6GC00137H, Paper

  Someshwar D. Dindulkar, Daham Jeong, Eunae Cho, Dongjin Kim, Seunho Jung
  A novel biosourced saccharide catalyst, microbial cyclosophoraose, a cyclic [small beta]-(1,2) glucan, was used for the synthesis of indolyl 4H-chromenes via a one pot three-component Knoevenagel-Michael addition-cyclization reaction in water under neutral conditions.

Microbial cyclosophoraose as a catalyst for the synthesis of diversified indolyl 4H-chromenes via one-pot three component reactions in water

 http://pubs.rsc.org/en/Content/ArticleLanding/2016/GC/C6GC00137H?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Microbial cyclosophoraose as a catalyst for the synthesis of diversified indolyl 4H-chromenes via one-pot three component reactions in water

Someshwar D. Dindulkar,^a   Daham Jeong,^a   Eunae Cho,^a  Dongjin Kim^b and   Seunho Jung*^ac  

*

Corresponding authors

^a

Institute for Ubiquitous Information Technology and Applications (UBITA) & Center for Biotechnology Research in UBITA (CBRU), Konkuk University, Seoul 143-701, South Korea 
E-mail: shjung@konkuk.ac.kr

^b

Nelson Mandela African Institution of Science and Technology, PO box 447, Arusha, Tanzania

^c

Department of Bioscience and Biotechnology, Microbial Carbohydrate Resource Bank (MCRB), Konkuk University, Seoul 143-701, South Korea

Green Chem., 2016, Advance Article

DOI: 10.1039/C6GC00137H

 As a novel biosourced saccharide catalyst, microbial cyclosophoraose, a cyclic β-(1,2) glucan, was used for the synthesis of therapeutically important versatile indolyl 4H-chromenes via a one pot three-component Knoevenagel–Michael addition–cyclization reaction of salicylaldehyde, 1,3-cyclohexanedione/dimedone, and indoles in water under neutral conditions. A possible reaction mechanism through molecular complexation is suggested based on 2D ROESY NMR spectroscopic analysis. Moreover, green chemistry metric calculations were carried out for a model reaction, indicating the satisfactory greener approach of this method, with a low E-factor (0.18) and high atom economy (AE = 91.20%). The key features of this protocol are based on two critical factors where the first is to use a novel eco-friendly supramolecular carbohydrate catalyst and the second is its fine green properties such as compatibility with various substituted reactants, recyclability of the catalyst, chromatography-free purification, high product selectivity, and clean conversion with moderate to excellent yields in an aqueous medium.

 9-(1H-indol-3-yl)-5-methoxy-3,3- dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one (4a):

 (2-hydroxy-3-methoxybenzaldehyde 1, Dimedone 2

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Two Catalysts for Reactions on the Double

Two Catalysts for Reactions on the Double

Synergistic catalysis gives the Morita–Baylis–Hillman reaction a big boost
Read more

Building-Block Compounds from Iodoaldol Reactions

The iodoaldol reaction of internal alkynyl ketones gives useful oxygen-functionalized vinyl iodides
Read more

Building-Block Compounds from Iodoaldol Reactions

Organic Synthesis Strategy and Control

Organic Synthesis Strategy and Control

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Shirong Lu, Weili Si, Ming Bao, Yoshinori Yamamoto, and Tienan Jin

WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan, and State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China

Org. Lett., Article ASAP

Publication Date (Web): July 23, 2013 (Letter)

DOI: 10.1021/ol401876n

http://pubs.acs.org/doi/abs/10.1021/ol401876n

An efficient and highly selective Co-catalyzed radical cycloaddition of [60]fullerene with active dibromides for the synthesis of three-, five-, six-, and seven-membered carbocycle-fused fullerene monoadducts has been reported. The controlled experiments unambiguously disclosed that the reaction proceeds through the formation of a fullerene monoradical as a key intermediate.

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Co-Catalyzed Radical Cycloaddition of [60]Fullerene with Active Dibromides: Selective Synthesis of Carbocycle-Fused Fullerene Monoadducts

Shirong Lu, Weili Si, Ming Bao, Yoshinori Yamamoto, and Tienan Jin

WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan, and State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China

Org. Lett., Article ASAP

Publication Date (Web): July 23, 2013 (Letter)

DOI: 10.1021/ol401876n

http://pubs.acs.org/doi/abs/10.1021/ol401876n

An efficient and highly selective Co-catalyzed radical cycloaddition of [60]fullerene with active dibromides for the synthesis of three-, five-, six-, and seven-membered carbocycle-fused fullerene monoadducts has been reported. The controlled experiments unambiguously disclosed that the reaction proceeds through the formation of a fullerene monoradical as a key intermediate.

Enantioselective Michael Addition

Coming on the heels of the very nice combined computational/experimental study of the enantioselective Strecker reaction by Jacobsen , there’s this JACS communication that really disappoints in its use of computational chemistry. Cobb uses yet another chiral thiourea to produce the enantioselective intramolecular Michael addition of nitronoates (Reaction1).¹ The reaction goes with excellent diastereoselectivity and eneatioselectivity, and can even be done with a substrate to produce three chiral centers. This is very nice synthetic chemistry.

Reaction 1. dr >19:1 ee 95%

The lack of reactivity of the Z ester suggested that the thiourea must associate with both the nitro group and the ester carbonyl. The authors provide a B3LYP/3-21G complex of thiourea with a simple nitroester (once again without providing coordinates in the supporting materials!) to demonstrate this sort of association. But this single structure, at this very low computational level, with these simplified reagents, and lacking solvent (see Rzepa’s comment) really makes one wonder just what value this computation provides. It also goes to demonstrate just how much effort Jacobsen went through to provide substantive computational support for his proposed mechanism of action.

References

(1) Nodes, W. J.; Nutt, D. R.; Chippindale, A. M.; Cobb, A. J. A., "Enantioselective Intramolecular Michael Addition of Nitronates onto Conjugated Esters: Access to Cyclic γ-Amino Acids with up to Three Stereocenters," J. Am. Chem. Soc. 2009, 131, 16016-16017, DOI: 10.1021/ja9070915

Do You Remember Darzen condensation Reaction

The Darzens reaction (also known as the Darzens condensation or glycidic ester condensation) is the chemical reaction of a ketone or aldehyde with an α-haloester in the presence of base to form an α,β-epoxy ester, also called a "glycidic ester".^[1][2] This reaction was discovered by the organic chemist Auguste George Darzens in 1904.^[3]

The reaction process begins when a strong base is used to form a carbanion at the halogenated position. Because of the ester, this carbanion is a resonance-stabilized enolate, which makes it relatively easy to form. This nucleophilic structure attacks another carbonyl component, forming a new carbon–carbon bond. These first two steps are similar to a base-catalyzed aldol reaction. The oxygen anion in this aldol-like product then does an intramolecular S_N2 attack on the formerly-nucleophilic halide-bearing position, displacing the halide to form an epoxide.^[4] This reaction sequence is thus a condensation reaction, since there is a net loss of HCl when the two reactant molecules join.Reaction mechanism

The primary role of the ester is to enable the initial deprotonation to occur, and other carbonyl functional groups can be used instead. If the starting material is an α-halo amide, the product is an α,β-epoxy amide.^[5] If an α-halo ketone is used, the product is an α,β-epoxy ketone.^[4]
Any sufficiently strong base can be used for the initial deprotonation. However, if the starting material is an ester, the alkoxide corresponding to the ester side-chain is commonly in order to prevent complications due to potential acyl exchange side reactions.

Stereochemistry

Depending on the specific structures involved, the epoxide may exist in cis and trans forms. A specific reaction may give only cis, only trans, or a mixture of the two. The specific stereochemical outcome of the reaction is affected by several aspects of the intermediate steps in the sequence.
The initial stereochemistry of the reaction sequence is established in the step where the carbanion attacks the carbonyl. Two sp³ (tetrahedral) carbons are created at this stage, which allows two different diastereomeric possibilities of the halohydrin intermediate. The most likely result is due to chemical kinetics: whichever product is easier and faster to form will be the major product of this reaction. The subsequent S_N2 reaction step proceeds with stereochemical inversion, so the cis or trans form of the epoxide is controlled by the kinetics of an intermediate step. Alternately, the halohydrin can epimerize due to the basic nature of the reaction conditions prior to the S_N2 reaction. In this case, the initially formed diastereomer can convert to a different one. This is an equilibrium process, so the cis or trans form of the epoxide is controlled by chemical thermodynamics--the product resulting from the more stable diastereomer, regardless of which one was the kinetic result.^[5]

Alternative reactions

Glycidic esters can also be obtained via nucleophilic epoxidation of an α,β-unsaturated ester, but that approach requires synthesis of the alkene substrate first whereas the Darzens condensation allows formation of the carbon–carbon connectivity and epoxide ring in a single reaction.

Subsequent reactions

The product of the Darzens reaction can be reacted further to form various types of compounds. Hydrolysis of the ester can lead to decarboxylation, which triggers a rearrangement of the epoxide into a carbonyl (4). Alternately, other epoxide rearrangements can be induced to form other structures.

References

1.  Darzens, G. (1905). Compt. Rend. 141: 766.
2.  Darzens, G. (1906). Compt. Rend. 142: 214.
3.  Darzens, G. (1904). Compt. Rend. 139: 1214.
4. Jie Jack Li (2006). "Darzens glycidic ester condensation". Name Reactions (3rd. expanded ed.). Springer-Verlag. pp. 183–184. doi:10.1007/3-540-30031-7.
5. Tung, C. C.; Speziale, A. J.; Frazier, H. W. (1963). "The Darzens Condensation. II. Reaction of Chloroacetamides with Aromatic Aldehydes". The Journal of Organic Chemistry 28 (6): 1514. doi:10.1021/jo01041a018. edit

Review articles

• Newman, M. S.; Magerlein, B. J. (1949). Org. React. 5: 413.
• Ballester, M. (1955). "Mechanisms of The Darzens and Related Condensations Manuel Ballester". Chem. Rev. 55 (2): 283. doi:10.1021/cr50002a002.
• Rosen, T. (1991). Comp. Org. Syn. 2: 409–439.

Camphor and Rivanol (Ethacridine Lactate) - An interesting reaction

Camphor and Rivanol (Ethacridine Lactate) - An interesting reaction

http://dailychem.blogspot.in/2011/11/camphor-and-rivanol-ethacridine-lactate.html

Two days ago, while trying to clean a pimple with an antiseptic camphor solution, I accidentally used ethacridine lactate (Rivanol) instead. After realizing this, instead of first cleaning the rivanol stain and then applying the camphor, I directly cleaned it with camphor using a cotton pad. Suddenly a new white layer formed at the contact surface between the two layers of substance. The occurrence of a chemical reaction was obvious, and after repeating the experiment in lab conditions, I tried to understand the formation of this new product.

Camphor structure

Rivanol structure  READ ALL THIS AT http://dailychem.blogspot.in/2011/11/camphor-and-rivanol-ethacridine-lactate.html

Quindine catalyzed synthesis of spirooxindoles through sequential Michael-Henry reactions.

A novel organocatalytic strategy for the synthesis of highly substituted spirocyclopentaneoxindoles was developed employing simple nitrostyrenes and 3-substituted oxindoles as starting materials. Michael–Henry cascade reactions, enabled through cinchona alkaloid organocatalysis, provided products in high yield and excellent enantioselectivity in a single step.

Spirooxindoles in one step

 DOI: 10.1021/ol300441z

http://pubs.acs.org/doi/abs/10.1021/ol300441z

If you just leaf through an organic chemistry journal, from JOC to Organic Letters, from EJOC to OBC, there is a huge number of papers describing synthesis of oxindoles! Indeed, the interest in the oxindoles scaffold rapidly increased in the last years and several methodologies have been published for the asymmetric synthesis of 3,3’-disubstituted oxindoles.

Cascade organacatalysis is a powerful tool for the for the asymmetric synthesis of very complex structures containing several stereogenic centers and oxindoles are optimal templates for the applications of these wonderful catalytic methodologies. For example, prof. Paolo Melchiorre, one the most expert in the organocatalysis field, published several works in the application of organocascade catalysis for the synthesis of quaternary oxindoles.

In this communication, Carlos Barbas, another pioneer of organocatalysis, reported a quindine-catalyzed synthesis of spirooxindoles through sequential Michael-Henry reactions.

They first performed a preliminary methodological study aimed at finding the most efficient catalyst, which turned out to be quindine derivative depicted below.

Subsequently the scope of the reaction has been expanded, by employing a wide range of substituted oxindoles, as well as different nitrostyrens. Performing the reaction at 0°C in CH2Cl2 as solvent in presence of quinidine derivative 1 permitted the isolation of the products in very high yield and optimal enantiomeric excess and diastereoisomeric ratio.

It is noteworthy to mention that this simple methodology permits the straightforward construction of the spirooxindole moiety containing four stereogenic centers,, with full control of the stereochemical outcome. This is another demonstration of the powerful of organocatalysis. 

http://pubs.acs.org/doi/abs/10.1021/ol300441z

Assembly of Spirooxindole Derivatives Containing Four Consecutive Stereocenters via Organocatalytic Michael–Henry Cascade Reactions

Klaus Albertshofer , Bin Tan , and Carlos F. Barbas, III*

The Skaggs Institute for Chemical Biology and the Departments of Chemistry and Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States

Org. Lett., 2012, 14 (7), pp 1834–1837

DOI: 10.1021/ol300441

Anthony crasto Presents Bombykol, a pheromone

Anthony crasto bombykol

by ANTHONY MELVIN CRASTO Ph.D

Anthony crasto Presents Bombykol, a pheromone

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Anthony crasto bombykol from ANTHONY MELVIN CRASTO Ph.D