Chemoselective, accelerated and stereoselective aza-Michael addition of amines to N-phenylmaleimide by using TMEDA based receptors

Deep Eutectic Solvent Choline Chloride/p-toluenesulfonic Acid and Water Favor the Enthalpy-Driven Binding of Arylamines to Maleimide in Aza-Michael Addition

Deep eutectic solvents (DESs) have been considered "the organic reaction medium of the century" because they can be used as solvents and active catalysts in chemical reactions. However, experimental and theoretical studies are still needed to provide information on the structures of DESs, the kinetics and thermodynamics properties, the interactions between the DESs and the substrates, the effect of water on the DES supramolecular network and its physicochemical properties, and so forth. This information is very useful to understand the essence of the processes that take place in the catalysis of chemical reactions and, therefore, to help in the design of a DES for a specific reaction and sample. This article shows a systematic study of the impact of DES choline chloride/p-toluenesulfonic acid and DES choline chloride/p-toluenesulfonic acid-water in the aza-Michael addition of arylamines to maleimide to obtain aminopyrrolidine-2,5-dione derivatives. The derivatives are obtained under very mild reaction conditions with good yield. The global reaction is exothermic, spontaneous, permitted by enthalpy, and prohibited for entropy. The calculated potential energy surface shows a reaction mechanism of six steps controlled by enthalpy (except the last step that is controlled by entropy). The water incorporated in the supramolecular DES complex stabilizes the transition states and favors the enthalpy-driven binding. A set of H/D exchange NMR experiments validates the transition state existing in the fourth stage of the mechanism.

Calcium(ii)-catalyzed enantioselective conjugate additions of amines

The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA]₂)-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed.

The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA]₂)-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed. This mild catalytic system represents a significant advance towards the general convergent asymmetric amination of α,β-unsaturated electrophiles, providing medicinally relevant chiral aminosuccinimide products in high yields and enantioselectivities. Furthermore, the catalyst can be reused directly from a previously chromatographed reaction and still maintain both high yield and selectivity.

Synthesis and Antifungal Studies of (2E)-N-Benzyl-N′-phenylbut-2-enediamide and (2E)-N,N′-Dibenzylbut-2-enediamide Analogues

A series of eleven butanediamine analogues, of which nine were new, were synthesized by the nucleophilic substitution of aromatic amines and benzylamines with maleic anhydride and tested on four yeast strains ofCandidaspecies using the broth microdilution method. Compounds3aand3cwith an unsubstituted phenyl ring and a 3-methoxyphenyl ring, respectively, are the most active against the fungal species with MIC values ranging from 20.2 to 80.6 μM forC. albicansandC. parapsilosisand 178.5 and 161.2 μM forC. krusei, respectively.

Automated radiosynthesis of the thiol-reactive labeling agent N-[6-(4-[18F]fluorobenzylidene)aminooxyhexyl]maleimide ([18F]FBAM)

The two-step radiosynthesis of N-[6-(4-[(18)F]fluorobenzylidene)aminooxyhexyl]maleimide ([(18)F]FBAM) was adapted to a remotely controlled synthesizer module. After optimization of reaction conditions as well as solid phase extraction based purification steps, the final [(18)F]FBAM was obtained in a decay-corrected radiochemical yield of 29±4% (related to [(18)F]fluoride, n=12) within a total synthesis time of 40 min. The radiochemical purity of [(18)F]FBAM was in the range 94-98%, the specific activity was determined with 13.4-17.2 GBq/μmol.

(S,S)-(+)-Pseudoephedrine as Chiral Auxiliary in Asymmetric Aza-Michael Reactions. Unexpected Selectivity Change when Manipulating the Structure of the Auxiliary

[reaction: see text] The asymmetric aza-Michael reaction of metal benzylamides to alpha,beta-unsaturated amides derived from the chiral amino alcohol (S,S)-(+)-pseudoephedrine has been studied in detail. A deep study of the most important experimental parameters (solvent, temperature, nucleophile structure, influence of additives) has been carried out, showing that the reaction usually proceeds with good yields and diastereoselectivities, although the experimental conditions have to be modified depending on the substitution pattern of the conjugate acceptor. Additionally, a very interesting facial selectivity inversion has been observed when manipulating the structure of the chiral auxiliary, which has allowed a diastereodivergent procedure to be set up for performing asymmetric aza-Michael reactions using the same chirality source. Finally, the adducts obtained in the asymmetric aza-Michael reaction have proven to be very versatile synthetic intermediates in the preparation of other interesting compounds such as beta-amino esters, gamma-amino alcohols, and beta-amino ketones in highly enantioenriched form.