Aqueous Morita-Baylis-Hillman reaction of unprotected isatins with cyclic enones

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

A straightforward synthetic protocol for the efficient construction of diazepine-containing spiroindolines has been developed and proceeds through a by base-promoted annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates. The reaction mechanism of this formal [4 + 3] annulation includes the in situ generated allylic ylide, nucleophilic substitution, Michael additon, and elimination processes. Additionally, the similar reaction with α-halogenated N-tosylhydrazones also afforded N-tosyl-substituted spiro[indoline-3,5'-[1,2]diazepine] in satisfactory yields. This protocol provides a convenient approach for the assembly of diverse highly functionalized spiro[indoline-3,5'-[1,2]diazepines] and also features a broad substrate scope, simple reaction conditions, and high molecular convergence.

Highly regioselective synthesis of lactams via cascade reaction of α,β-unsaturated ketones, ketoamides, and DBU as a catalyst

Herein, the aldol/Michael cascade reaction on the β,γ-positions of α,β-unsaturated ketones with ketoamides to construct bicyclic lactams via DBU catalysis has been developed. The substrates were well-tolerated with high regio- and diastereoselectivities in moderate to good yields (32 examples). The control experiments revealed that the hydrogen of the amide was the key factor.

Synthesis and Evaluation of N-Diaminophosphoryl Aminothioureas as Bifunctional Catalysts for Vinylogous Aldol Reactions of Isatins and 2(3H)-Furanones

The organocatalytic asymmetric direct vinylogous aldol reaction of N-methylisatins 1 and γ-butenolides 2 to provide 3-hydroxy-2-oxindole derivatives 3 was investigated. A series of N-diaminophosphoryl aminothiourea catalysts 4 was synthesized, and their utility for the stereoselective formation of 3 was examined.

Micelle-guided Morita-Baylis-Hillman reaction of ketones in water

A novel Morita-Baylis-Hillman reaction employing electron-deficient alkenes like acrylonitrile with a wide range of aryl and aliphatic ketones using cooperative catalysis in micellar media has been delineated. This transformation executed in water under mild reaction conditions in a confined environment of micelles is aligned to the ideas of sustainable and green chemistry. The site of the reaction was established by incisive proton NMR studies in the palisade region of the micellar assembly. This study is expected to encourage the use of micellar catalysis for energetically less favorable chemical reactions.

An Artificial Cofactor Catalyzing the Baylis-Hillman Reaction with Designed Streptavidin as Protein Host*

An artificial cofactor based on an organocatalyst embedded in a protein has been used to conduct the Baylis-Hillman reaction in a buffered system. As protein host, we chose streptavidin, as it can be easily crystallized and thereby supports the design process. The protein host around the cofactor was rationally designed on the basis of high-resolution crystal structures obtained after each variation of the amino acid sequence. Additionally, DFT-calculated intermediates and transition states were used to rationalize the observed activity. Finally, repeated cycles of structure determination and redesign led to a system with an up to one order of magnitude increase in activity over the bare cofactor and to the most active proteinogenic catalyst for the Baylis-Hillman reaction known today.

Brønsted-acid-catalyzed selective Friedel-Crafts monoalkylation of isatins with indolizines in water

The controlled mono-addition of indolizines to isatins under very mild conditions is described. The reaction occurs in water using diphenylphosphate as the catalyst, which is dramatically accelerated by surfactant addition. 3-Hydroxy-3-indolizinyl-2-oxindole scaffolds were synthesized in up to >99% yield. Notably, in organic solvents only bis-addition products were observed.

Discovery of highly potent and selective antiparasitic new oxadiazole and hydroxy-oxindole small molecule hybrids

A series of highly active hybrids were discovered as novel antiparasitic agents. Two heterocyclic scaffolds (1,2,4-oxadiazole and 3-hydroxy-2-oxindole) were linked, and the resulting compounds showed in vitro activities against intracellular amastigotes of two protozoan parasites, Trypanosoma cruzi and Leishmania infantum. Their cytotoxicity was assessed using HFF-1 fibroblasts and HepG2 hepatocytes. Compounds 5b, 5d, 8h and 8o showed selectivity against L. infantum (IC₅₀ values of 3.89, 2.38, 2.50 and 2.85 μM, respectively). Compounds 4c, 4q, 8a and 8k were the most potent against T. cruzi, exhibiting IC₅₀ values of 6.20, 2.20, 2.30 and 2.20 μM, respectively. Additionally, the most potent anti-T. cruzi compounds showed in vitro efficacies comparable or superior to that of benznidazole. These easy-to-synthesize molecules represent novel chemotypes for the design of potent and selective lead compounds for Chagas disease and leishmaniasis drug discovery.

Diastereoselective synthesis of dispiro[indoline-3,3′-furan-2′,3′′-pyrrolidine] via [3 + 2]cycloaddition reaction of MBH maleimides of isatins and 1,3-dicarbonyl compounds

In the presence of mixed bases DABCO and K₂CO₃, the reaction of MBH maleimides of isatins with various cyclic 1,3-dicarbonyl compounds afforded functionalized dispiro[indoline-3,3′-furan-2′,3′′-pyrrolidines] in satisfactory yields and with high diastereoselectivity.

Vinyl-1,2,4-oxadiazoles Behave as Nucleophilic Partners in Morita-Baylis-Hillman Reactions

We describe that vinyl-oxadiazoles function as a new and efficient nucleophilic partner for the Morita-Baylis-Hillman (MBH) reaction. The reaction between 5-vinyl-3-aryl-1,2,4-oxadiazoles and aromatic and aliphatic aldehydes, catalyzed by DABCO in the absence of solvent, showed high efficiency to afford a new class of heterocyclic MBH adducts with potential biological activity on yields up to 99% and short reaction times. These synthetically attractive adducts bear a heterocyclic scaffold of large pharmaceutical and commercial interest associated with a plethora of biological effects and technological applications. We also demonstrate their synthetic usefulness by a photoinduced addition reaction to a polyfunctionalized amino alcohol.

Amino acid ionic liquids as catalysts in a solvent-free Morita–Baylis–Hillman reaction

In the present work, we describe the preparation of ten amino acid ionic liquids (AAILs) formed from ammonium salts as cations, derivatives of glycerol, and natural amino acids as anions. All of them are viscous oils, colorless or pale yellow, and hygroscopic at room temperature. They have appreciable solubility in many protic and aprotic polar solvents. The AAILs were used as catalysts in a Morita–Baylis–Hillman (MBH) reaction. The ionic liquids derivative from l-proline and l-histidine demonstrated the ability to catalyze the reaction between methyl vinyl ketone and aromatic aldehydes differently substituted in the absence of an additional co-catalyst under organic solvent-free conditions. The AAIL derivatives from l-valine, l-leucine, and l-tyrosine catalyzed the MBH reaction only in the presence of imidazole. The MBH adducts were obtained in moderate to good yields. Although the catalytic site in the ILs was in its enantiomerically pure form, all the MBH adducts were obtained in their racemic form.

In this work, we describe the preparation of ten amino acid ionic liquids (AAILs). The AAILs were used as catalysts in a Morita–Baylis–Hillman (MBH) reaction. The MBH adducts were obtained from moderate to good yields and in their racemic form.

Morita-Baylis-Hillman reaction of acrylamide with isatin derivatives

The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

An intermolecular C–H functionalization method for the synthesis of 3-hydroxy-2-oxindoles

An intermolecular C–H functionalization with a denitrosation-triggered cyclization method is developed for the synthesis of 3-hydroxy-2-oxindoles.