Showing posts with label catalyst. Show all posts

Saturday 13 July 2013

Anthony crasto presents Buckyball or Buckminsterfullerene

Anthony crasto buckyball

by ANTHONY MELVIN CRASTO Ph.D

Anthony crasto buckyball or Buckminsterfullerene presentation, helping millions, million hits on google

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Anthony crasto buckyball from ANTHONY MELVIN CRASTO Ph.D

Wednesday 3 July 2013

REARRANGEMENT REACTION Prepared by:Ashwini.M.Londhe

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rearrangement reaction from ashwinilondhe

Sunday 30 June 2013

Beckmann rearrangement

The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is an acid-catalyzed rearrangement of an oxime to an amide. Cyclic oximes yield lactams.

This example reaction starting with cyclohexanone, forming the reaction intermediate cyclohexanone oxime and resulting in caprolactam is one of the most important applications of the Beckmann rearrangement, as caprolactam is the feedstock in the production of Nylon 6.
The Beckmann solution consists of acetic acid, hydrochloric acid and acetic anhydride, and was widely used to catalyze the rearrangement. Other acids, such as sulfuric acid or polyphosphoric acid, can also be used. sulfuric acid is the most commonly used acid for commercial lactam production due to its formation of an ammonium sulfate by-product when neutralized with ammonia. Ammonium sulfate is a common agricultural fertilizer providing nitrogen and sulfur.

The Beckmann rearrangement is an organic reaction used to convert an oxime to an amide under acidic conditions. The reaction begins by protonation of the alcohol group forming a better leaving group. The R group trans to the leaving group then migrates to the nitrogen, resulting in a carbocation and the release of a water molecule. This trans [1-2]-shift allows for the prediction of the regiochemistry of this reaction. The water molecule then attacks the carbocation and after deprotonation and tautomerization results in the final amide product.

lactam, a monomer for the production of Nylon 12.

Beckmann reaction

SEE BELOW ILLUSTRATION IN

http://www.mdpi.com/1420-3049/17/11/13662

Upon treatment with phenyl dichlorophosphate (PhOP=OCl₂) in acetonitrile at ambient temperature, a variety of ketoximes underwent a Beckmann rearrangement in an effective manner to afford the corresponding amides in moderate to high yields.

Thursday 6 June 2013

DRUG SYNTHESIS PORTALS ON THE NET

http://newdrugapprovals.wordpress.com/drug-synthesis/

Thursday 23 May 2013

One-Pot Method for Regioselective Bromination and Sequential Carbon–Carbon Bond-Forming Reactions of Allylic Alcohol Derivatives

One-Pot Method for Regioselective Bromination and Sequential Carbon–Carbon Bond-Forming Reactions of Allylic Alcohol Derivatives

European Journal of Organic Chemistry Noriki Kutsumura, Yusuke Matsubara, Kentaro Niwa, Ai Ito and Takao Saito
DOI: 10.1002/ejoc.201300173

http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201300173/abstract

Di- or trisubstituted olefins were synthesized in high yields with excellent regio- and cis–trans selectivities in one-pot reactions, including a regioselective DBU-promoted trans HBr elimination. This one-pot methodology could become a straightforward transformation of “straight” alkenes into “Y-shaped” alkenes.

An efficient one-pot method for the regioselective bromination of allylic alcohol derivatives (two-step reaction sequence) followed by Sonogashira, Negishi, or Suzuki–Miyaura coupling reactions in the same reaction vessel (three-step reaction sequence) has been developed. The key reaction in these one-pot systems is the regioselective DBU-promoted trans HBr elimination of vicinal dibromides bearing an adjacent O-functional group.

Synthetic Uses of Ammonia in Transition-Metal Catalysis

Synthetic Uses of Ammonia in Transition-Metal Catalysis (pages 3201–3213)

European Journal of Organic Chemistry

Jinho Kim, Hyun Jin Kim and Sukbok Chang
DOI: 10.1002/ejoc.201300164

Although ammonia (NH₃) is a cheap, abundant, and readily available nitrogen source, it has rarely been used in transition-metal catalysis, due to several obstacles. However, significant advances in the metal-mediated utilization of ammonia have been made recently. This review presents the most recent examples in metal-mediated amination and other relevant reactions with ammonia or ammonium salts.
http://onlinelibrary.wiley.com/doi/10.1002/ejoc.201300164/abstract

Ammonia (NH₃) is a cheap, abundant, and readily available nitrogen source, being one of the chemicals produced in the greatest quantities. Whereas ammonia is utilized mainly as a feedstock for the production of fertilizers, it is also employed in industry as a component of various nitrogen-containing compounds. In metal catalysis, in contrast, ammonia has been used only with limited success, due to several difficulties such as generation of stable Lewis acid-base adducts, facile ligand exchange for ammonia in active metal complexes, a propensity towards undesired second transformations of initially formed species, and the requirement for special equipment to run the reactions. Despite these obstacles, the direct use of ammonia in catalysis has continuously attracted great interest, leading recently to significant progress. Whereas liquid or gaseous ammonia were most commonly employed in the past, under harsh conditions, notable catalytic reactions using easy-to-handle ammonium salts under milder and more convenient conditions have now been developed. In this review we briefly describe the most recent examples of transition-metal-catalyzed reactions using ammonia or ammonium salts.