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Showing posts with label ORGANIC REACTIONS. Show all posts
Showing posts with label ORGANIC REACTIONS. Show all posts

Friday, 6 December 2013

Selection of boron reagents for Suzuki–Miyaura coupling

Graphical abstract: Selection of boron reagents for Suzuki–Miyaura coupling

 Suzuki–Miyaura (SM) cross-coupling is arguably the most widely-applied transition metal catalysed carbon–carbon bond forming reaction to date. Its success originates from a combination of exceptionally mild and functional group tolerant reaction conditions, with a relatively stable, readily prepared and generally environmentally benign organoboron reagent. A variety of such reagents have been developed for the process, with properties that have been tailored for application under specific SM coupling conditions. This review analyses the seven main classes of boron reagent that have been developed. The general physical and chemical properties of each class of reagent are evaluated with special emphasis on the currently understood mechanisms of transmetalation. The methods to prepare each reagent are outlined, followed by example applications in SM coupling.

Review Article

Selection of boron reagents for Suzuki–Miyaura coupling

Corresponding authors
School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK

Chem. Soc. Rev., 2014,43, 412-443

DOI: 10.1039/C3CS60197H
Received 12 Jun 2013, First published online 03 Oct 2013 

Friday, 8 November 2013

Conversion of sugars to ethylene glycol with nickel tungsten carbide in a fed-batch reactor: high productivity and reaction network elucidation

Green Chem., 2013, Advance Article
DOI: 10.1039/C3GC41431K, Paper
Roselinde Ooms, Michiel Dusselier, Jan A. Geboers, Beau Op de Beeck, Rick Verhaeven,
Elena Gobechiya, Johan A. Martens, Andreas Redl, Bert F. Sels
Fed-batch reactor technology was used for the highly productive conversion of
concentrated sugar solutions into ethylene glycol using bifunctional nickel tungsten
carbide catalysts.

Conversion of sugars to ethylene glycol with nickel tungsten carbide

 in a fed-batch reactor: high productivity and reaction 

network elucidation





 Bifunctional nickel tungsten carbide catalysis was used for the conversion of aqueous sugar

 solutions into short-chain polyols such as ethylene glycol. It is shown that very concentrated sugar 

solutions, viz. up to 0.2 kg L−1, can be converted without loss of ethylene glycol selectivity 

by gradually feeding the sugar solution. Detailed investigation of the reaction network

 shows that, under the applied reaction conditions, glucose is converted via a retro-aldol

 reaction into glycol aldehyde, which is further transformed into ethylene glycol by hydrogenation. 

The main byproducts are sorbitol, erythritol, glycerol and 1,2-propanediol. 

They are formed through a series of unwanted side reactions including 

hydrogenation, isomerisation, hydrogenolysis and dehydration. 

Hydrogenolysis of sorbitol is only a minor source of ethylene glycol. To assess the 

relevance of the fed-batch system in biomass conversions, both the influence of the

 catalyst composition and the reactor setup parameters like temperature, pressure 

and glucose addition rate were optimized, culminating in ethylene glycol yields up to 66% and

 separately, volume productivities of nearly 300 gEG L−1 h−1.

Tuesday, 29 October 2013

Synthesize 7-azanorbornane on an industrial scale

Synthesize 7-azanorbornane on an industrial scale
Patent Number:US 8404865
Title:Process for preparing azabicyclic compounds
Inventor(s):Ambhaikar, Narendra Bhalchandra; Bear, Brian Richard; Fanning, Lev T. D.; Hughes, Robert; Littler, Benjamin
Patent Assignee(s):Vertex Pharmaceuticals Incorporated, USA
Source:U.S. Pat. Appl. Publ., 8pp. CODEN: USXXCO
Abstract:The present invention relates to a process for prepg. azabicyclic compds. that are useful intermediates for synthesizing pharmaceutical compds. or salts thereof.  Thus, azabicyclo[2.2.1]heptane hydrochloride (I·HCl) was prepd. from trans-4-aminocyclohexanol via N-protection with Boc2O in CH2Cl2 contg. Et3N; mesylation with MsCl in CH2Cl2 contg. Et3N; N-deprotection with CF3CO2H; cyclization with aq. NaOH; and treatment with
7-azabicyclo[2.2.1]heptanes are useful intermediates in the synthesis of pharmaceutical compounds and salts thereof. For example, see U.S. Pat. Nos. 6,117,889 and 6,060,473, each of which is hereby incorporated by reference in its entirety
 Despite the title of N. B. Ambhaikar and co-inventors’ patent, “Process for preparing azabicyclic compounds”, it only describes a process for preparing 7-azanorbornane (5) and its HCl salt (6). The inventors state that compound 5 is an intermediate in the synthesis of pharmaceutical compounds, but they do not mention any.

The patent’s examples describe the preparation of 5 and its precursors on a kilogram scale. The first step is protecting the amino group in 1 by converting it to tert-butoxycarbonyl (BOC) derivative 2 with the anhydride (BOC)2O in the presence of Na2CO3. The product is isolated in 88.8% yield. The reaction can also be carried out with K2CO3, but the yield is not reported.
Four-step synthesis of 7-azanorbornane
In the second step, 2 is treated with methanesulfonyl chloride (MsCl) in the presence of Et3N to form methanesulfonate 3 in 96.6% isolated yield. In step three, the BOC group is removed by adding CF3CO2H in two batches. The product is amine salt 4. The recovered salt contains excess CF3CO2H; and as a result, the yield appears to be >100%.
In the final stage, the CF3CO2H salt is treated with NaOH to cyclize it to the desired compound. Azanorbornane 5 is recovered by fractional distillation; treating the fractions with concd HCl gives hydrochloride salt 6. The salt is recovered as a solid, dried, and recrystallized from MeOH and MeOH–THF. Although the examples contain significant detail, the product’s final yield and purity are not reported.
The process is an efficient method for preparing 7-azanorbornane and its salt. It is clearly suitable for large-scale production. (Vertex Pharmaceuticals [Cambridge, MA]. US Patent 8,404,865, March 26, 2013; Keith Turner)
 7-azanorbornane HCl salt (6). 
1HNMR (DMSO-d6) ppm 8.02-8.04 (d); 7.23-7.31 (m); 4.59 (s); 3.31 (s); 2.51-3.3 (m); 1.63-1.75 (m); 1.45-1.62 (m).

In one aspect, the invention includes a process for preparing Compound 7-azanorbornane
Figure US08404865-20130326-C00001
    • or a pharmaceutically acceptable salt thereof, comprising contacting trans-4-aminocyclohexanol with Boc anhydride to produce a compound of formula A
Figure US08404865-20130326-C00002
    • contacting a compound of formula A with methanesulfonic acid to produce a compound of formula B
Figure US08404865-20130326-C00003
    • contacting a compound of formula B with trifluoroacetic acid to produce a compound of formula C
Figure US08404865-20130326-C00004
    • contacting a compound of formula C with hydroxide to produce a compound of formula 
In some embodiments, the invention includes a method of producing a compound of formula 7-azanorbornane Hydrocloride salt
Figure US08404865-20130326-C00005
    • The TFA salt of trans-4-aminocyclohexylmethanesulfonate (200 g, 650.9 mmol) was introduced into a 3-necked flask followed by the addition of water (2.200 L, 11 vol). NaOH (78.11 g, 1.953 mol, 3 eq) was slowly added, keeping the temperature of the reaction mixture below 25° C. and the mixture was stirred overnight. DCM (1.4 L, 7 vol) was then added and the mixture stirred, and the organic layer was separated. The aqueous layer was then extracted a second time with DCM (1.4 L, 7 vol), and the DCM layers were combined. HCl (108.5 mL, 12M, 1.3020 mol, 2 eq) was then added, the mixture was stirred for 30 min and then concentrated on a rotary evaporator to dryness. Acetonitrile (10 vol) was added and the mixture concentrated. This was repeated 3 times until all trace water was azeotropically removed, to provide 7-azabicyclo[2.2.1]heptane hydrochloride. The crude product was recrystallized from acetonitrile (10 vol) to provide 7-azabicyclo[2.2.1]heptane hydrochloride as a colorless crystalline solid.

Wednesday, 16 October 2013

Microwave-assisted synthesis of N-heterocycles in medicinal chemistry

Med. Chem. Commun., 2013, 4,1323-1343
DOI: 10.1039/C3MD00152K, Review Article
Davide Garella, Emily Borretto, Antonella Di Stilo, Katia Martina, Giancarlo Cravotto, Pedro Cintas
Microwave-assisted synthesis of heterocycle libraries has given an impressive contribution to drug discovery and development.http://pubs.rsc.org/en/Content/ArticleLanding/2013/MD/C3MD00152K?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FMD+%28RSC+-+Med.+Chem.+Commun.+latest+articles%29#!divAbstract

Microwave-assisted synthesis of N-heterocycles in medicinal chemistry



 The syntheses of almost all N-heterocycles have now been successfully performed under microwave irradiation and have provided significant improvements in the reaction time and efficiency. The peculiar properties of dielectric heating give it the ability to strongly promote cyclocondensation, cycloaddition and selective N-heterocycle functionalisation and it has, therefore, very much caught the attention of the medicinal chemistry community. In this work, we present an overview of recent literature and technical advances in this research field with the aim of providing insight into the applications of microwave-assisted synthesis in the preparation of the main drug categories that contain N-heterocycle scaffolds.

Monday, 14 October 2013

A Novel Solid-Phase Synthesis of Quinolines

Short Paper | Regular issue | Vol 85, No. 3, 2012, pp.667-676
Published online: 26th January, 2012
DOI: 10.3987/COM-11-12411
 A Novel Solid-Phase Synthesis of Quinolines
E Tang,* Deshou Mao, Wen Li, Zhangyong Gao, and Pengfei Yao
*School of Chemical Science and Technology, Yunnan University, No. 2 Green Lake North Road, Kunming 650091, China
A method for synthesizing substituted-quinolines using TMSOTf-catalyzed polystyrene-supported succinimidyl selenide-induced intramolecular seleno-arylation of tethered alkenes as a key step has been developed. The catalytic process provides an efficient method for the stereoselective and regioselective synthesis of tetrahydroquinoline possessing a seleno-functionality, followed by deprotection of tosyl group and syn-elimination of selenoxides to provide quinolines in good yields and purities.


Sunday, 1 September 2013

Synthesis of Tolvaptan

Synthesis of Tolvaptan

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YANG Chuanwei~1,MU Shuai~2,LIU Ying~3,WANG Pingbao~3,LIU Dengke~(3*) 
(1.School of Pharmacy,Henan University,Kaifeng 475004;2.
School of Chemical Engineering and Technology,
 Tianjin University,Tianjin 300072;3.
Tianjin Institute of Pharmaceutical Research,Tianjin 300193)  
Tolvaptan,a selective nonpeptide arginine vasopressin V_2 receptor antagonist,was synthesized
 from 7-chloro-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine by acylation and reduction to give 1-(4-amino-2-methylbenzoyl) -7- chloro-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine,which was subjected to acylation with 2-methylbenzoyl chloride and reduction with sodium borohydride with an overall yield of about 45%.
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
Chinese Journal Full-text Database2 Hits
1LI Fan1, HOU Xingpu2, LI Lin1, LU Tao1, DU Yumin1 (1. School of Pharmacy,
Hebei Medical University, Shijiazhuang 050017; 2. Shijiazhuang
 Pharma Group NBP Pharmaceutical Co., Ltd., Shijiazhuang 052160);
Synthesis of Antiparkinsonian Agent Istradefylline[J];Chinese Journal of Pharmaceuticals;2010-04
2YANG Miao~1,SHUAI Jun~2,LIU Mo~3,LIU Deng-ke~(3*),WANG Ping-bao~3
(1.Tianjin Medical University,Tianjin 300070;2.Tianjin University;Tianjin 300072;
 3.Tianjin Institute of Pharmaceutical Research,Tianjin 300193);
Synthesis of 7-Chloro-5-oxo-2,3,4,5-tetrahydro-1H-1-benzazepine[J];
Chinese Journal of Pharmaceuticals;2009-09
Chinese Journal Full-text Database1 Hits
1XIONG Xiao-yi,CHEN An-qun,HE Yong-mei(Chongqing Unis Chemical Co.,Ltd.,Chongqing
402161,China);Analysis of Cyanoacetic Acid Content by HPLC[J];Guangzhou Chemical Industry;2010-12

Friday, 2 August 2013