Bifunctional Thiourea Research Articles

ChemInform Abstract: Construction of Highly Enantioselective Spiro‐Oxindole Derivatives with Fused Chromene via Organocascade Catalysis.

A first highly enantioselective addition of naphthols and sesamol to indolylidene cyanoacetate derived from isatins was carried out in the presence of bi-functional quinine thiourea as organocatalyst. Under optimized reaction conditions the present catalytic system gave spiro-oxindole derivatives with excellent yield and enantioselectivity (up to 99%) at very low catalyst loading (2 mol%). The absolute configuration of 3i was determined by single X-ray crystallographic analysis to be the S isomer of the product. A catalytic cycle is proposed based on NMR, IR and kinetic studies.

Kinetically Controlled α‐Selective O‐Glycosylation of Phenol Derivatives Using 2‐Nitroglycals by a Bifunctional Chiral Thiourea Catalyst

AbstractThe highly α‐selective organocatalytic glycosylation of phenol derivatives using 2‐nitroglycals has been developed. The stereoselectivity of this reaction was kinetically controlled by a bifunctional thiourea catalyst, the chirality of which was crucial for obtaining the high α‐selectivity. A variety of phenol derivatives were added to 2‐nitrogalactal with excellent stereoselectivity. The reaction of 2‐nitroglucal also achieved highly stereoselective glycosylation. The reaction was applied to the synthesis of glycopeptides.

Bifunctional Thioureas with α-Trifluoromethyl or Methyl Groups: Comparison of Catalytic Performance in Michael Additions.

Thioureas are an important scaffold in organocatalysis because of their ability to form hydrogen bonds that activate substrates and fix them in a defined position, which allows a given reaction to occur. Structures that enhance the acidity of the thiourea are usually used to increase the hydrogen-bonding properties, such as 3,5-bis(trifluoromethyl)phenyl and boronate ureas. Herein, we report the synthesis of bifunctional thioureas with a chiral moiety that include either a trifluoromethyl or methyl group. Their catalytic performance in representative Michael addition reactions was used in an effort to compare the electronic effects of the fluorination at the methyl group. The observed differences concerning yields and ee values cannot be attributed solely to the different steric environments; theoretical results indicate distinct interactions within the corresponding transition states. The calculated transition states show that the fluorinated catalysts have stronger N-H···O and C-H···F hydrogen bonds, while the nonfluorinated systems have C-H···π contacts. These results have shown that a variety of hydrogen-bonding interactions are important in determining the yield and selectivity of thiourea organocatalysis. These details can be further exploited in catalyst design.

Construction of Polycyclic Fused Pyrrolidines with Three Contiguous Stereocenters via Michael Addition of Vinylmalononitriles to Nitrostyrenes­ Using l-Proline-Derived Thiourea

The catalytic efficiency of a bifunctional chiral thiourea derived from <sc>l</sc>-proline was evaluated in the asymmetric direct vinylogous Michael reaction of α,α-dicyanoolefins to β-nitrostyrenes with an electron-releasing or electron-withdrawing substituent in various positions. The corresponding adducts were isolated in good yields, with excellent diastereo- (>99%) and enantioselectivity (up to 95%). The Michael adducts were further functionalized to achieve the synthesis of polycyclic fused pyrrolidines with three contiguous stereocenters in good enantioselectivities.

Development of Bifunctional Thiourea Organocatalysts Derived from a Chloramphenicol Base Scaffold and their Use in the Enantioselective Alcoholysis of meso Cyclic Anhydrides

AbstractThe synthesis of new chloramphenicol‐base‐derived thiourea organocatalysts, (1S,2R)‐12 a–f and (1R,2R)‐15 a–c, and their use in the enantioselective alcoholysis of meso‐anhydrides are described. In particular, hemiesters afforded excellent enantioselectivities if low loadings of (1S,2R)‐12 a–f were used. Almost no enantioselectivities were achieved with the use of (1R,2R)‐15 a–c. This technique was used to synthesize (R)‐(−)‐baclofen.

ChemInform Abstract: Novel Efficient Bifunctional Calixarene Thiourea Organocatalysts: Synthesis and Application in the Direct Enantioselective Aldol Reactions.

AbstractA novel bifunctional calixarene thiourea CLXA is prepared and successfully applied as chiral catalyst for enantioselective aldol reactions of aryl aldehydes with acetone.

ChemInform Abstract: Supported Bifunctional Thioureas as Recoverable and Reusable Catalysts for Enantioselective Nitro‐Michael Reactions.

AbstractFour bifunctional thioureas supported on sulfonylpolystyrene resins are studied as catalysts in the stereoselective nitro‐Michael addition of various nucleophiles to trans‐β‐nitrostyrene derivatives.

ChemInform Abstract: Organocatalytic Construction of Spirooxindole Naphthoquinones Through Michael/Hemiketalization Using‐Proline Derived Bifunctional Thiourea.

ChemInformVolume 47, Issue 25 Heterocyclic Compounds ChemInform Abstract: Organocatalytic Construction of Spirooxindole Naphthoquinones Through Michael/Hemiketalization Using-Proline Derived Bifunctional Thiourea. V. Pratap Reddy Gajulapalli, V. Pratap Reddy Gajulapalli Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorKanduru Lokesh, Kanduru Lokesh Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorManjunatha Vishwanath, Manjunatha Vishwanath Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorVenkitasamy Kesavan, Venkitasamy Kesavan Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this author V. Pratap Reddy Gajulapalli, V. Pratap Reddy Gajulapalli Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorKanduru Lokesh, Kanduru Lokesh Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorManjunatha Vishwanath, Manjunatha Vishwanath Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this authorVenkitasamy Kesavan, Venkitasamy Kesavan Dep. Biotechnol., Indian Inst. Technol., Chennai 600 036, IndiaSearch for more papers by this author First published: 02 June 2016 https://doi.org/10.1002/chin.201625103Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume47, Issue25June, 2016 RelatedInformation

Towards the total synthesis of keramaphidin B.

The enantio- and diastereoselective Michael addition of a δ-valerolactone-derived pronucleophile to a substituted furanyl nitroolefin catalysed by a bifunctional cinchonine-derived thiourea has been used as the key stereocontrolling step in a new synthetic strategy to the heavily functionalised piperidine core of keramaphidin B.

Dynamic Kinetic Resolution of Biaryl Lactones via a Chiral Bifunctional Amine Thiourea-Catalyzed Highly Atropo-enantioselective Transesterification.

A solution to the unmet synthetic challenge of achieving highly atropo-enantioselective transesterification of Bringmann's lactones has been realized, employing a chiral bifunctional amine thiourea as promoter. The synergistic activation of the lactones and alcohols/phenols by the respective thiourea and amine groups is crucial for achieving the highly enantioselective, high-yielding dynamic kinetic resolution process. This protocol gives highly optically pure, axially chiral biaryl compounds with a broad substrate scope under mild reaction conditions.

ChemInform Abstract: Highly Enantioselective Michael Addition of Malononitrile to α,β‐Unsaturated Pyrazolamides Catalyzed by a Bifunctional Thiourea.

AbstractThe Michael addition of malononitrile (II) to α,β‐unsaturated pyrazolamides [(I), (IV), (VI), or (VIII), resp.] is accomplished by the use of bifunctional thioureas as catalysts.

ChemInform Abstract: Asymmetric Synthesis of Dihydrocoumarins Containing Contiguous Quaternary and Tertiary Stereogenic Centers Catalyzed by a Cinchona‐Alkaloid‐Based Bifunctional Thiourea Derivative.

A series of enantiomerically enriched 3,4-dihydrocoumarins containing contiguous quaternary and tertiary stereogenic centers has been efficiently constructed via domino asymmetric Michael addition/transesterification reactions of azlactones with o-hydroxychalcones using a quinine-derived thiourea as bifunctional organocatalyst. Under mild reaction conditions, the optically active 3,4-dihydrocoumarins were generally obtained in 63–96% yields with >20:1 dr and 81–96% ee.

ChemInform Abstract: Asymmetric Synthesis of Spiroketals with Aminothiourea Catalysts.

AbstractThe intramolecular bis‐cyclization of α,β‐unsaturated carbonyl compounds (I) tethered with an hydroxy substituted alkylketone side chain is optimized in the presence of bifunctional thiourea catalyst to give spiroketals.

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

The catalytic activity of different supported bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well.

Advances on Asymmetric Organocatalyzed Mannich Reactions in Aqueous and Non-aqueous Media

Considerable number of nitrogen containing active pharmaceutical ingredients and natural products are frequently synthesized from optically pure β-amino ketones, aldehydes, esters, and alcohols. Synthesis of 1,3-amino ketones, aldehydes, alcohols and esters engages Mannich-type reactions, the most important basic reaction-types in organic chemistry. The current trend in the development of asymmetric Mannich-type reaction is to employ unmodified ketones and aldehydes as starting materials in the presence of simple and easily accessible metal-free organocatalysts under mild and convenient reaction conditions. Although L-Proline and its derivatives are commonly and extensively studied organocatalysts in Mannich reactions, many other organocatalysts based on bifunctional thiourea, chiral Bronsted acids and some other organocatalytic systems are also equally effective. The present review comprehensively describes an overview of asymmetric Mannich reactions under different organocatalytic systems in both organic and aqueous media. Keywords: Aminoalkylation, asymmetric synthesis, aqueous media, C-C bond formation, chiral bronsted acids, Mannich reaction, organic media, organocatalysis, L-proline, thioureas.

ChemInform Abstract: Asymmetric Cycloaddition Reactions Catalyzed by Bifunctional Thiourea and Squaramide Organocatalysts: Recent Advances

AbstractReview: 64 refs.

ChemInform Abstract: Asymmetric Dearomatization of β‐Naphthols Through a Bifunctional‐Thiourea‐Catalyzed Michael Reaction.

AbstractAn interesting asymmetric dearomatization of β‐naphthols is achieved by Michael reaction with nitroethane as reaction partner using a bifunctional chiral thiourea as catalyst.

Novel efficient bifunctional calixarene thiourea organocatalysts: synthesis and application in the direct enantioselective aldol reactions

Novel efficient bifunctional calixarene thiourea organocatalysts have been designed as efficient organocatalysts for direct asymmetric aldol reactions between acetone and aromatic aldehydes. The reactions generated the corresponding products in satisfactory isolated yields (up to 96%) and with excellent enantiomeric excesses (up to 99%) in the presence of catalyst (10mol %).

ChemInform Abstract: Enantioselective Synthesis of Highly Substituted Chromans via the Oxa‐Michael—Michael Cascade Reaction with a Bifunctional Organocatalyst.

A highly enantioselective synthesis of chiral chroman derivatives via an oxa-Michael–Michael cascade reaction has been developed using a bifunctional thiourea organocatalyst. The products were obtained with excellent enantioselectivities (up to >99%), good yields (up to 95%), and diastereoselectivities (up to 5:1).

The First Enantioselective Organocatalytic Synthesis of 3-Spiro-α-Alkylidene-γ-Butyrolactone Oxindoles.

A new and flexible methodology catalyzed by bifunctional chiral thioureas has been developed to react β-nitro oxindoles 1 with aldehydes. This approach allowed us to achieve the first enantioselective organocatalytic synthesis of 3-spiro-α-alkylidene-γ-butyrolactone oxindoles 3. We examined the scope of the two starting materials and, varying the structure of the β-nitro oxindole 1, intriguing new products, derived from unexpected transformations, have been stereoselectively obtained. The aim of this study was to merge two potentially bioactive structural motifs: the spirooxindole substructure and the α-alkylidene-γ-butyrolactone moiety. A preliminary NMR study on the ability to reversibly trap 2-aminoethanethiol gave us promising results.