Equ 13. 4-(5-nolyl)-Pyridinum Cation Containing CILs Catalyzed Aldol Reactions Equ 14. Amide Functionalized Proline based CILs Organocatalyst for Aldol Reactions 3.4. Asymmetric Diels-Alder reaction. In 1997, Howarth and his group80 reported first, the asymmetric Diels-Alder reaction by using dialkylimidazolium salts (chiral and achiral) as efficient organocatalyst between crotonaldehyde or methacrolein and cyclopentadiene. The enentiomeric excess was less than 5% and no such diastereoselectivity were observed. Here enantiomeric excess did not depends upon the ionic liquids chirality, both chiral CILs and achiral CILs gave the near about same results. After that time researchers have been tried to design and synthesized Lewis acid based …show more content…
The anionic CIL N-methylimidazolium (R)-camphorsulfonate was employed in the reaction with methyl vinyl ketone (Equ 19). After Michael addition, N-(3ꞌ-oxobutyl)-N-methylimidazolium (R)-camphorsulfonate was obtained. Using heterogeneous catalyst Ru/C in the hydrogenation reaction of this imidazolium cation functionalized carbonyl group to produce corresponding asymmetric alcohol gave moderate yield and enantioselectivity 80% ee was …show more content…
Enantioselective hydrogenation of keto functionalized ionic liquid. The field of asymmetric hydrogenation reactions using metal complexes has been well developed. These complexes are generated from assymmtric chiral ligands such as atropoisomeric binaphthyls and biphenyls. In 2007, Francio and group88 reported asymmetric hydrogenation reaction catalyzed by tropoiosmeric ligand based rhodium complex in presence of amino acid based CIL 71 as a chiral solvent. In this reaction the chirality of hydrogenated product arises from CILs and enantioselectivities up to 69% ee were observed (Equ 20). In 2008, the same group89 reported hydrogenation reaction using transition metal complex with racemic ligands instead of enantiopure ligands in presence of CILs. The same results were observed by using both the racemic ligands and enantiomerically pure ligands (Equ 20). These results were observed mainly due to the chiral poisoning by the CILs in racemic 2,2ꞌ-bis(diphenylphosphanyl)-1,1ꞌ-binaphthyl ligands which was connecting with metals. Equ 20. Enantioselective hydrogenation in amino acid-based CILs. 3.6. Biginelli
Click here to unlock this and over one million essaysShow More
For this experiment, stereochemistry was observed by analyzing both the isomerization of dimethyl maleate and carvones. The dimethyl maleate is formed by two methyl ester groups that are connected by an alkene. They are in a cis-conformation meaning they are on the same side of the alkene, therefore the esters are close to one another. This conformation is strained and sterically hindered due to electrons repelling each other and are enantiomers of one another. With the use of radical chemistry, the cis conformation can be changed into a trans configuration where the esters are on opposite sides of one another.
The abundant of esters, which serves as the electron withdrawal group, propels the effectiveness of this reaction. In the present case, the central ring of the anthracene possesses the characteristic properties of a diene, electron-rich, system . Thus, this aromatic compound reacts with the 9 and 10 positions of the maleic anhydride dienophile, electron-poor, by 4 +2 cycloaddition . 9 and 10 are the position of preference because it is where new bonds can be made without destroying the aromatic formation of the other two rings. This reaction results in a six-membered ring bridged on the 9 and 10 positions of anthracene.
Chloroacetic acid (0.5 g, 5. 28 mmol), 5-aminotetrazole monohydrate (0.45 g, 5. 28 mmol), and sodium hydroxide (0.59 g, 10.57 mmol) in 10 ml of water was refluxed 20 hr, cooled, and made strongly acidic with concentrated hydrochloric acid. The mixture was cooled overnight and precipitate was separated to give 0.28 g a white solid product at 45.41% yield. (5-Amino-tetrazol-1-yl)-acetic acid: Yield: 45.41%; white crystals; m.p 210-213°C; IR (KBr): 3388, 3315, 3270, 3205, 3010, 2976, 1697, 1638, 1586, 1496, 1257 cm-1; 13C NMR (75 MHz (DMSO-d6)): 168, 156,
The goal of this experiment was to synthesize the unknown ester through Fischer Esterification. This procedure involves treating a carboxylic acid with an alcohol and a strong acid catalyst. This procedure was also catalyzed with heat at 160oC-180oC, to keep the temperature from exceeding the boiling points of the compounds in use. The acid catalyst protonated the double bonded oxygen atom to force the atom to pull two electrons away from the double bond in order to stabilize the atom’s charge. As this electron shift occurred, the alcohol attacked the carbocation that lost its double bond.
Introduction:- In organic chemistry the substitution reactions is the most important reactions, especially Nucleophilic aromatic substitution reactions where nucleophile attacks positive charge or partially positive charge As it does so, it replaces a weaker nucleophile which then becomes a leaving group. The remaining positive or partially positive atom becomes an electrophile. The general form of the reaction is: Nuc: + R-LG → R-Nuc + LG: The electron pair (:) from the nucleophile (Nuc :) attacks the substrate (R-LG) forming a new covalent bond Nuc-R-LG.
The major research question of my studies is if cyclooctyne can be successfully reacted with a vinylketene complex using a cost-effective methodology and in producing a distinct organic complex. In this experiment, a tricarbonyl iron(0) vinylketene complex was reacted with cyclooctyne in a cycloaddition reaction. The method used in this experimentation was based on the fundamentals of Click Chemistry. Since, reactions designed according to the concepts of Click Chemistry produced inoffensive byproducts and high yields, it was hypothesized that this reaction would produce a new methodology in how to synthesize cyclooctyne reacted complexes and produce an unknown organic complex. The primary goal in this research was to form an unknown* complex
The reactions of 2-bromo-2H-azirine with methylamine led to the synthesis of alpha-diimines. 2-Halo- 2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 10a-10d, 3-oxazoline, and 2H-[1,4]oxazines.32 Chemical reactions are described for the formation of aziridine-2-one and di-azirine-3-one derivatives as potential precursors for the original synthesis of amino-acids, proteins, pyrimidines, purines, nicotinamide and flavin.33
The process of acid-catalyzed hydration of an alkene to and alcohol has valuable properties with practical uses. Naturally, as an alkene, norbornene is not very reactive. It has a strong pi bond, and is also non-polar. However, by hydrating norbornene with the assistance of an acid-catalyst, norborneol is formed. Norborneol, being an alcohol, is much more reactive and has the potential to be further reacted to obtain a certain product.
1. Introduction Friedel–Crafts acylation of aromatic compounds is one of the most important and practical methods to prepare aromatic ketones. The resulting diaryl ketones are important chemical intermediates for the synthesis of a wide range of compounds such as pharmaceuticals, fragrances, flavors, dyes and agrochemicals [1,2]. This is an electrophilic acylation of aromatic compounds with acid chlorides or acid anhydrides, which is traditionally catalyzed by Lewis acids, such as AlCl3, BF3, SbCl5, FeCl3, ZnCl2, SnCl4, TiCl4 or strong protonic acids, such as H2SO4, HF [3-7]. The major drawbacks of these catalysts are that they are hazardous, corrosive, non-recoverable and usually more than stoichiometric amounts of catalysts are required.
According to the simulated NMR spectra of CA, TA and saccharin by ACD-ilab software (34), hydroxyl functional groups of them have a single peak at ~10 ppm which in is upfield to ~6 ppm in ionized from whenever the first carboxylic acids was converted to carboxylate (COO−). In SAC, disappearance of a single peak at 8.1 ppm of saccharin confirm ionization of 1,2-benzisothiazole ring of SAC. CVD has no peak in the studied regions (8 ppm and ~6 ppm for ionized form of SAC and studied carboxylic acid, respectively). Similar spectra (Figure S1 in supplementary information) of CVD-CA and CVD-TA show the appearance of a peak at ~6 ppm. It established the ionization of the first carboxylic acid of CA and TA and salt formation.
Subsequently, we attempted preliminary examination by choosing 5-methoxy -2-phenyl oxazole (2a) as starting material to proceed whether Friedel–Crafts reaction. Although the normal conditions which used Lewis acid such as AlCl3 or TiCl4 with TFAA in DCE did not proceed to acylation, the reaction of introducing trifluoroacetyl group at the C4-position of oxazole without Lewis acid gave substituted oxazole (4a). Contrary to our expectations, isolated oxazole had been not trifluoroacetylated derivative (3a), reaching rearrangement compound (4a) in one step．After our optimization of the acylated condition, the use of 1.3 equivalents of TFAA and THF as a solvent and condition of the temperature at 60 degrees for 22 hr led 90%
CHAPTER III BIGINELLI REACTION INTRODUCTION Dihydropyrimidinones (DHPMs), commonly known as Biginelli compounds, have attained unprecedented attention due to its greater biological, pharmaceutical and therapeutic properties. In 1893, Pietro Biginelli reported the first synthesis of 3,4-dihydroprimidin-2(1H)ones (DHPM) by a very simple multi-component one-pot condensation reaction of an aromatic aldehyde, urea and ethyl acetoacetate in ethanolic solution1 (Scheme 1.1). This efficient approach to partly reduced pyrimidines, termed the Biginelli reaction or condensation, was largely ignored in the following years, and therefore, also the synthetic potential of these multi-functionalized dihydropyrimidines remained unexplored. In recent years, however, interest in these compounds has increased rapidly, and the scope of the original cyclocondensation reaction has been widely extended by variation of all three components. Scheme 1.1.
3. Results and discussion 4-Chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) is an activated aryl halide that has been used as a chromogenic and fluorogenic reagent for the determination of many drugs with primary and secondary amino groups [22-24]. The reaction of NBD-Cl with LBT has not been investigated yet. LBT contain secondary amino group which can react with NBD-Cl in alkaline medium to form a yellowish green colored product. This derivative exhibited maximum fluorescence intensity at 540 nm after excitation at 476 nm (Figure 2), the maximum absorbance of the reaction product was measured at 480 nm (Figure 3).