52406-22-1Relevant articles and documents
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
supporting information, p. 17500 - 17507 (2017/12/15)
Although iminium catalysis has become an important tool in organic chemistry, its combination with supramolecular host systems has remained largely unexplored. We report the detailed investigations into the first example of iminium catalysis inside a supramolecular host. In the case of 1,4-reductions of α,β-unsaturated aldehydes, catalytic amounts of host are able to increase the enantiomeric excess of the products formed. Several control experiments were performed and provided strong evidence that the modulation of enantiomeric excess of the reaction product indeed stems from a reaction on the inside of the capsule. The origin of the increased enantioselectivity in the capsule was investigated. Furthermore, the substrate and nucleophile scope were studied. Kinetic investigations as well as the kinetic isotope effect measured confirmed that the hydride delivery to the substrate is the rate-determining step inside the capsule. The exploration of benzothiazolidines as alternative hydride sources revealed an unexpected substitution effect of the hydride source itself. The results presented confirm that the noncovalent combination of supramolecular hosts with iminium catalysis is opening up new exciting possibilities to increase enantioselectivity in challenging reactions.
Synthesis of Fatty Acetoacetates Under Microwave Irradiation Catalysed by Sulfamic Acid in a Solvent-Free System
Weber, Andressa C. H.,Batista, Thaís C.,Gon?alves, Bruno,Hack, Carolina R. L.,Porciuncula, Larissa M.,Treptow, Tamara G. M.,D’Oca, Caroline Da R. Montes,Russowsky, Dennis,D’Oca, Marcelo G. Montes
, p. 1399 - 1406 (2016/09/28)
The 1,3-dicarbonyl compounds are important building blocks to obtain products with various biological activities and technological applications. In this work, we used a simple transesterification method to develop fatty acetoacetates in a solvent-free medium using a green catalyst, sulfamic acid (NH2SO3H), under microwave irradiation. The experimental results demonstrate good yields in a short reaction time (13?min), which makes this method an efficient approach to synthesize fatty acetoacetates from a wide range of saturated, unsaturated, and polyunsaturated long chain fatty alcohols, and ricinoleic derivatives. Experiments of recycling of the catalyst were performed and no decrease in catalytic activity of sulfamic acid was observed.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
supporting information, p. 7698 - 7701 (2016/07/07)
The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
Efficient transesterification of ethyl acetoacetate with higher alcohols without catalysts
Koval,Dzyuba,Ilnitska,Pekhnyo
, p. 1645 - 1647 (2008/09/19)
The transesterification of ethyl acetoacetate (EtOAcac) without the use of catalysts is shown for primary, secondary and tertiary alcohols. The use of molecular sieves, which are used to shift the equilibrium, allows the synthesis of products in high yields and acceptable reaction times, which are on a par with those for transesterification processes using catalysts. The kinetics of the transesterification of EtOAcac with tert-amyl alcohol is studied.
Synthesis and structural study of new highly lipophilic 1,4-dihydropyridines
Suarez, Margarita,De Armas, Merly,Ramirez, Oney,Alvarez, Amaury,Martinez-Alvarez, Roberto,Molero, Dolores,Seoane, Carlos,Liz, Ramon,De Armas, Hector Novoa,Blaton, Norbert M.,Peeters, Oswald M.,Martin, Nazario
, p. 1567 - 1576 (2007/10/03)
A new series of 1,4-dihydropyridines (1,4-DHPs) endowed with ester groups bearing long and functionalised alkoxy chains at the C3 and C5 positions of the nitrogen ring have been prepared from the corresponding β-keto esters which were in turn prepared by a lipase catalysed transesterification reaction. The structural study has been carried out by X-ray crystallography and theoretical calculations at the semiempirical (AM1), ab initio (HF/6-31G*) and B3LYP/6-31G* levels and reveals that the long alkyl chains do not have any influence on the required geometry of the 1,4-DHPs for biological activity. However, these chains have a strong impact on the lipophilicity and, therefore, they could be used to gain a better control of the duration of the pharmacological action. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.
Solvent-free microwave-assisted organic reactions prepation of β-keto esters
Gianotti, Massimo,Martelli, Giorgio,Spunta, Giuseppe,Campana, Eileen,Panunrio, Mauro,Mendozza, Monica
, p. 1725 - 1730 (2007/10/03)
Microwave technique has been utilised in the preparation of β-keto esters. Two different procedures are described: transesterification of β- keto esters and ring opening of 2,2,6-trimethyl-1,3-dioxin-4-one.
Liquid oligomers containing acrylate unsaturation
-
, (2008/06/13)
The liquid oligomeric compositions of this invention are made by the Michael addition reaction of acetoacetate functional donor compounds with multifunctional acrylate receptor compounds where the equivalent ratios of multifunctional acrylate to acetoacetate vary from >/=1:1 to >/=13.2:1 depending on the functionality of both multifunctional acrylate and acetoacetate. Unuseable gelled or solid oligomer products occur below the claimed ranges. The liquid oligomers of this invention are further crosslinked to make coatings, laminates and adhesives.
Selective Catalytic Transesterification, Transthiolesterification, and Protection of Carbonyl Compounds over Natural Kaolinitic Clay
Ponde, Datta E.,Deshpande, Vishnu H.,Bulbule, Vivek J.,Sudalai, Ammugam,Gajare, Anil S.
, p. 1058 - 1063 (2007/10/03)
Transesterification and transthiolesterification of β-keto esters with variety of alcohols and thiols and selective protection of carbonyl functions with various protecting groups catalyzed by natural kaolinitic clay are described. The clay has been found to be an efficient catalyst in transesterifying long chain alcohols, unsaturated alcohols, and phenols to give their corresponding β-keto esters in high yields. For the first time, transthiolesterification of β-keto esters with a variety of thiols has been achieved under catalytic conditions. Clay also catalyzes selective transesterification of β-keto esters by primary alcohols in the presence of secondary and tertiary alcohols giving corresponding β-keto esters. A systematic study involving the reactivity of different nucleophiles (alcohols, amines, and thiols) toward β-keto esters is also described. Sterically hindered carbonyl groups as well as α,β-unsaturated carbonyl groups underwent protection without the deconjugation of the double bond. Chemoselective protection of aldehydes in the presence of ketones has also been achieved over natural kaolinitic clay.
Simple and high yielding syntheses of β-keto esters catalysed by zeolites
Balaji,Chanda, Bhanu M.
, p. 13237 - 13252 (2007/10/03)
Simple and high yielding syntheses of several β-keto esters, catalysed by zeolite Hβ are reported. The methods developed include condensation of aldehydes with ethyl diazoacetate and transesterification of β-keto esters with primary, secondary, allylic and benzylic alcohols etc., all catalysed by Hβ. It was further observed that under microwave irradiation the yields of many aromatic β-keto esters were enhanced appreciably.
A facile and selective synthesis of β-keto esters via zeolite catalysed transesterification
Balaji,Sasidharan,Kumar, Rajiv,Chanda, Bhanu
, p. 707 - 708 (2007/10/03)
Crystalline microporous aluminosilicates (zeolites) efficiently catalyse the transesterification of β-keto esters with high selectivity under environmentally safe reaction conditions.
