Facile and highly diastereoselective synthesis of 3-aminooxindoles via AgOAc-catalyzed vinylogous Mannich reaction

A novel AgOAc-catalyzed vinylogous Mannich reaction between easily prepared imines 1 derived from isatins and trimethylsilyloxyfuran 2 (TMSOF) was developed. This method provided a facile synthetic route to get access to synthetically useful quaternary 3-aminooxindole in excellent yields (94–99%) and diastereoselectivities (>99:1).     

A robust, efficient catalyst system for enolate arylation leading to quaternary 3-aminooxindoles

A catalyst screening programme has revealed that a combination of Pd(0) and the N-heterocyclic carbene ligand SIPr forms a particularly robust and efficient catalyst for the formation of important quaternary 3-aminooxindoles via intramolecular enolate arylation. Catalyst loadings of 0.1 mol % give complete conversion in under 4 h.     

Aqueous single step synthesis and structural characterization of allylated,propargylated, and benzylated 3-substituted 3-aminooxindoles

Efficient zinc-mediated allylation, propargylation, and benzylation of isatin-derived imines were undertaken for the synthesis of 3-substituted 3-aminooxindoles with ≈80% yield. Such alternative approach has efficiently avoided the use of catalysts, severe reaction conditions, multistep procedures, and reaction additives. For exploring and materializing the synthetic utility, different allyl, propargyl, and benzyl bromides were used for generalizing the synthetic route. The structure of the synthesized compounds was established and confirmed by ¹H NMR, ¹³C NMR, FTIR, and mass spectroscopic techniques.     

Enantioselective and solvent-controlled diastereoselective Mannich reaction of isatin imines with hydroxyacetone: synthesis of 3-substituted 3-aminooxindoles

The diastereoselectively switchable enantioselective Mannich reaction of isatin imines with hydroxyacetone is reported. The chiral primary amino acid catalyzed this Mannich reaction to afford both anti- and syn-Mannich adducts in high yields, good diastereoselectivities, and enantioselectivities. The reason for the solvent control of the diastereoselectivity phenomenon was investigated.     

Recent advances in the asymmetric catalytic synthesis of chiral 3-hydroxy and 3-aminooxindoles and derivatives: Medicinally relevant compounds

Several oxindole derivatives, of natural or synthetic origin, have been identified as medicinally appealing compounds, with a plethora of bioactivities reported. Chiral 3-hydroxy and 3-aminooxindole scaffolds have captured the attention of several research groups, due to their importance in drug discovery. In this review, we systematically address the wide variety of asymmetric catalytic methodologies employed in the preparation of these relevant chiral scaffolds, present in many biologically active compounds and/or natural products. Special focus will be given to the nature of the catalyst used.     

A catalytic metal-free Ritter reaction to 3-substituted 3-aminooxindoles

The first Ritter reaction of 3-substituted 3-hydroxyoxindoles with nitriles, catalyzed by HClO(4), is developed, which enables the synthesis of 3-substituted 3-aminooxindoles in good to excellent yield with rich diversity.     

Facile and regioselective synthesis of phenylpropanoid-substituted flavan-3-ols

[reaction: see text] A highly efficient, facile, one-pot regioselective synthesis of a series of phenylpropanoid-substituted flavan-3-ols is described. The mechanism involves dienone-phenol rearrangement followed by a Michael-type reaction.     

Facile synthesis of 3‐spiroindolines

Cyanoacetyldiazoindol‐2‐one ( 3 ), the condensation product of cyanoacetohydrazide with isatin ( 1 ), could be cyclized in acidic medium via its CN group and its enolic OH to give cyanomethyloxadiazole‐spiroindoline ( 4 ). The presence of the methylcyano side chain could be invested—through oximation, diazotization, or condensation with aldehydes—to form polyfunctional spiroindolines 5, 8–10 . Also, a second route for preparing the title compound could be achieved through a nucleophilic attack on position 3 in the isatin derivatives, followed by subsequent ring closure to give 6 and 7 . © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:207–210, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10020     

Facile synthesis and high d33 of single-crystalline KNbO3 nanocubes

Single-crystalline KNbO(3) nanocubes with orthorhombic phase were prepared in a large scale by a simple one-step molten salt route without using any surfactant as template; the nanostructures exhibited high piezoelectric properties such as d(33)=105 pC/N and k(p)=0.34 as piezoelectric materials.     

十五碳内酯的简易合成法

以中国西南地区的油料植物蒜头果油(Kernal oil),经皂化得到的二十四碳-15-烯酸为原料.通过臭氧化和硼氢化还原反应得到ω-羟基十五碳烷酸.以碳酸钾为催化剂,聚乙二醇为相转移催化剂使后者缩聚和解聚可以91%的得率制得十五碳内酯.在合成过程中,用正交试验和方差分析找出最佳实验条件.该大环内酯具有良好的定香作用.     

Facile synthesis of troilite

Low-temperature synthetic pathways can result in crystallization of metastable materials. These methods have been widely explored for the preparation of metal oxides. Adaptation of nonhydrolytic sol-gel chemistry to non-oxide systems offers an elegant route to transition-metal sulfides. The method can be exploited for the facile and reproducible synthesis of iron sulfide crystallizing in the troilite structure. This phase is only found in meteorites and planets and has previously been obtained by high-temperature or high-energy ball-milling methods. "Nonhydrolytic" sol-gel processing results in direct crystallization of troilite with no need for further calcination.     

Facile synthesis of gamma-alkylidenebutenolides

In this paper, a novel route to gamma-alkylidenebutenolides (gamma-AIBs) by way of stereoselective vinylogous aldol reaction of the unactivated butenolide in simple and general conditions is reported.     

A facile synthesis of 3-aryl pyroglutamic acid. Facile synthesis of baclofen and chlorpheg

A facile synthesis of 3-aryl pyroglutamic acids via stepwise [3+2] annulation and desulfonated hydrolysis is reported. Base-induced coupling/cyclization reactions of α-sulfonylacetamide with various β-functional groups of (Z)-2-bromoacrylates yielded three contiguous chiral centers on the polysubstituted pyroglutamates system with trans-trans orientation in a one-pot synthesis. This facile strategy was used to synthesize amino acid derivatives baclofen and chlorpheg.     

Facile synthesis of furobenzothiazepines

The reaction of methyl 5-(2-isocyanatophenylthio)-2-furancarboxylate 2 with N-methylpiperazine gave 5-(2-N-piperazinocarbamoylphenylthio)-2-furancarboxylate 3a . Furthermore, 4-N-methylpiperazinyl-2-methoxycarbonylfuro[2,3-b][1,5]benzothiazepine 4a was obtained by the Bischler-Napieralski reaction of 3a with phosphorus oxychloride in the present of phosphorus pentoxide. Three furobenzothiazepines could be obtained using the same method. Based on the pharmacological studies of these compounds, it was found that 4-morpholinyl-2-methoxycarbonylfuro[2,3-b][1,5]benzothiazepine 4b had anti-inflammatory activity similar to flufenamic acid.     

Facile synthesis of asymmetric quaternary centers based on diastereoselective protection of the carbonyl group at the symmetrical position

The C2-side chain hydroxyl group of 1,3-cycloalkanedione discriminates between two ketones depending on its chirality. It chooses one ketone to form hydrogen bond with the oxygen atom of the TBDPS-oxymethyl group, but chooses the other ketone upon conversion to the isopropyl acetal. Two optically pure diastereomers, whose absolute configuration at the angular position is opposite for each other, were thus synthesized from this single chiral source through simple operations. This method may be applied for the synthesis of a variety of compounds with asymmetric quaternary centers.     

Cinnolines. X. The oxidative-rearrangement of 1-aminooxindoles to 3-cinnolinols

An improved route for the oxidative-rearrangement of 1 -aminooxindoles, treatment with equimolar amounts of t-butyl hypochlorite, produces nearly quantitative yields of 3-cinnolinols of excellent purity. The syntheses of the previously inaccessible 4- and 6-ehloro-1-armnooxin-doles has shown that this method, first applied to 1-aminooxindole, may be reasonably general. The mechanism of this reaction is discussed in terms of nitrene and nitrenoid intermediates.     

Facile synthesis of meso-arylamino- and alkylaminosubporphyrins

Newcomers: meso-Arylamino- and meso-alkylaminosubporphyrins have been synthesized by the Pd-catalyzed aminations of meso-bromosubporphyrin 1 as the first example of subporphyrins containing heteroatom substituents at the meso-position. The X-ray structural analyses have revealed significant structural distortions of meso-aminosubporphyrins 2 due to the effective electronic interaction (see scheme).     

Facile and green synthesis of dapagliflozin

A facile and green synthetic route was developed for the preparation of dapagliflozin (1), a selective sodium-dependent glucose cotransporter 2 inhibitor for the treatment of type 2 diabetes. Key reaction steps include a direct Friedel–Crafts acylation and a synthesis of diaryl ketal moiety in one-pot manner without waste water generation. Furthermore, the reduction of the diaryl ketone and C-phenylglucoside were achieved in one-pot manner to generate dapagliflozin (1) more efficiently. The synthetic route featured the usage of commercial available and easily handling reagents with shorter reaction steps and less waste disposal.     

Facile synthesis of new oxalate dimers of naturally occurring 3-hydroxysteroids

Several symmetrical steroidal oxalate dimers were synthesised from naturally occurring 3-hydroxysteroids, namely, estrone (1), DHEA (3), pregnenolone (5), cholesterol (7), 5D-cholestane (9), and stigmasterol (11), using oxalyl chloride. Full spectroscopic data for all the new compounds are presented. Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 442–444, September–October, 2006.