Catalytic Version Research Articles

Catalytic Wittig and aza-Wittig reactions.

This review surveys the literature regarding the development of catalytic versions of the Wittig and aza-Wittig reactions. The first section summarizes how arsenic and tellurium-based catalytic Wittig-type reaction systems were developed first due to the relatively easy reduction of the oxides involved. This is followed by a presentation of the current state of the art regarding phosphine-catalyzed Wittig reactions. The second section covers the field of related catalytic aza-Wittig reactions that are catalyzed by both phosphine oxides and phosphines.

ChemInform Abstract: Catalytic Asymmetric Synthesis of Bicycloprolines by a 1,3‐Dipolar Cycloaddition/Intramolecular Alkylation Strategy.

The diastereoselective one-pot synthesis of hexahydrocyclopenta[b]pyrrole derivatives (bicycloprolines) has been achieved by base-mediated reactions of (E)-tert-butyl 6-bromo-2-hexenoate with α-imino esters. The catalytic asymmetric version of this process has been efficiently achieved using the CuI/(R)-DTBM-Segphos complex as a catalyst following a two-step 1,3-dipolar cycloaddition/intramolecular alkylation sequence.

Carbocation catalyzed carboxylic acid activation in Staudinger reaction for stereoselective synthesis of β-lactams

A novel strategy to synthesize stereoselective β-lactams has been disclosed via cyclopropenium-ion-catalyzed reaction of substituted acetic acids with aldimines under mild conditions. Products are formed in high yields (86–95%) and good diastereoselectivity within 3–4h. The new reaction is focused on the exploration of the scope of cyclopropenium-ion catalysis and introduction of a catalytic version of one-step Staudinger reaction for β-lactam synthesis. The reaction is effective for a range of substituted acetic acids and aldimines.

Sn-based catalysts for Baeyer-Villiger oxidations by using hydrogen peroxide as oxidant

Baeyer-Villiger (BV) oxidation is one of the most important transformation reactions in synthetic organic chemistry. Catalytic versions of the BV oxidation are particularly attractive in practical applications, because the catalytic transformation substantially simplifies reaction process while minimizing reactant consumption as well as waste production. Further benefits are expected from replacing peracids, the traditionally used oxidant, by low cost and environmentally friendly hydrogen peroxide (H2O2). This review will first introduce very briefly the features of BV oxidation reactions, and the corresponding oxidants traditionally used. Afterwards, the emphasis will be placed on the specific Sn-based catalysts, their performance comparison for the BV oxidation reaction by using H2O2 as oxidant, and the catalytic mechanisms of most Sn-based catalysts reported so far, including homogeneous Sn-based catalysts (such as Sn-based fluorous biphase system catalysts), heterogeneous Sn-based catalysts (such as Sn-based zeolite catalysts, Sn-based mesoporous composites, Sn-incorporated clay catalysts, Sn-based metal oxide composites and polymer supported Sn catalysts). Finally, the Sn-based catalysts for BV oxidation are outlooked for their potentials and perspectives in enhancing the performance and then accelerating the practical applications of BV oxidations by using H2O2. The developing direction of the Sn-based catalytic BV reaction is also illustrated.

Direct Hydroxylation and Amination of Arenes via Deprotonative Cupration.

Deprotonative directed ortho cupration of aromatic/heteroaromatic C-H bond and subsequent oxidation with t-BuOOH furnished functionalized phenols in high yields with high regio- and chemoselectivity. DFT calculations revealed that this hydroxylation reaction proceeds via a copper (I → III → I) redox mechanism. Application of this reaction to aromatic C-H amination using BnONH2 efficiently afforded the corresponding primary anilines. These reactions show broad scope and good functional group compatibility. Catalytic versions of these transformations are also demonstrated.

Catalytic Asymmetric Synthesis of Bicycloprolines by a 1,3-Dipolar Cycloaddition/Intramolecular Alkylation Strategy.

The diastereoselective one-pot synthesis of hexahydrocyclopenta[b]pyrrole derivatives (bicycloprolines) has been achieved by base-mediated reactions of (E)-tert-butyl 6-bromo-2-hexenoate with α-imino esters. The catalytic asymmetric version of this process has been efficiently achieved using the Cu(I)/(R)-DTBM-Segphos complex as a catalyst following a two-step 1,3-dipolar cycloaddition/intramolecular alkylation sequence.

ChemInform Abstract: Trichloromethanesulfonyl Chloride: A Chlorinating Reagent for Aldehydes.

Trichloromethanesulfonyl chloride (CCl3SO2Cl), a commercially available reagent, has been found to perform efficiently in the α-chlorination of aldehydes, including its catalytic asymmetric version, under very mild reaction conditions. Under our reaction conditions, this compound outperforms typical chlorinating reagents for organic synthesis, facilitates workup and purification of the product, and minimizes the formation of toxic, chlorinated organic waste.

Enantioselective Carbene Cascade: An Effective Approach to Cyclopentadienes and Applications in Diels–Alder Reactions

AbstractAn asymmetric carbene cascade reaction, which proceeds through carbene/alkyne metathesis and formal (3+2) cycloaddition and converts alkynyl‐tethered enol diazoacetates to chiral bicyclic cyclopentadienes, is presented; and no catalytic asymmetric version of these carbene cascade transformations has been disclosed so far. The proton signals of the cyclopropene intermediates are observed in the mechanism study, which clearly demonstrate the reaction pathways. In addition, these products are intercepted via Diels–Alder reactions to provide bridged polycyclic structures in high yields and enantioselectivities.magnified image

ChemInform Abstract: Brook/Elimination/Aldol Reaction (BEAR) Sequence for the Direct Preparation of Fluorinated Aldols from β,β‐Difluoro‐α‐(trimethylsilyl)alcohols.

A methodology allowing the preparation of aldols featuring a fluorinated stereogenic center is reported. The corresponding fluoroenolates are formed in situ from stable β,β-difluoro-α-(trimethylsilyl)alcohols, through a base-mediated process involving a Brook rearrangement followed by a fluoride elimination, and are directly added to aromatic aldehydes. Two different sets of conditions were disclosed. The first one involves the stoichiometric addition of potassium tert-butoxide (t-BuOK) while the second is based on the use of a catalytic amount of an ammonium phenoxide. The latter opens the way for a catalytic and asymmetric version of this Brook/elimination/aldol reaction (BEAR) sequence.

ChemInform Abstract: Organocatalyzed Trifluoromethylation of Ketones and Sulfonyl Fluorides by Fluoroform under a Superbase System.

AbstractA new catalytic version of fluoroform trifluoromethylation is developed which is applicable to a wide variety of diaryl, aryl‐alkyl, and dialkyl ketones (I) and arylsulfonyl fluorides (IV).

Trichloromethanesulfonyl Chloride: A Chlorinating Reagent for Aldehydes.

Trichloromethanesulfonyl chloride (CCl3SO2Cl), a commercially available reagent, has been found to perform efficiently in the α-chlorination of aldehydes, including its catalytic asymmetric version, under very mild reaction conditions. Under our reaction conditions, this compound outperforms typical chlorinating reagents for organic synthesis, facilitates workup and purification of the product, and minimizes the formation of toxic, chlorinated organic waste.

A Neber approach for the synthesis of spiro-fused 2H-azirine-pyrazolone.

A base-mediated Neber reaction of enaminopyrazolones, which are the tautomers of 4-acyloxime-2-pyrazolin-5-ones, with sulfonyl chlorides was achieved. With this developed approach, a range of spiro-fused 2H-azirine-pyrazolones were obtained in good yields under mild conditions. A preliminary trial of a catalytic asymmetric version of the Neber reaction was conducted and gave promising enantioselectivity.

A well-defined low-valent cobalt catalyst Co(PMe3)4 with dimethylzinc: a simple catalytic approach for the reductive dimerization of benzyl halides

We report a simple catalytic version of a cobalt-catalysed reductive homocoupling of benzyl halides by combining Co(PMe3)4 and Me2Zn.

Richard F. Heck (1931-2015).

Richard F. Heck (1931-2015).

Brook/Elimination/Aldol Reaction (BEAR) Sequence for the Direct Preparation of Fluorinated Aldols from β,β‐Difluoro‐α‐(trimethylsilyl)alcohols

AbstractA methodology allowing the preparation of aldols featuring a fluorinated stereogenic center is reported. The corresponding fluoroenolates are formed in situ from stable β,β‐difluoro‐α‐(trimethylsilyl)alcohols, through a base‐mediated process involving a Brook rearrangement followed by a fluoride elimination, and are directly added to aromatic aldehydes. Two different sets of conditions were disclosed. The first one involves the stoichiometric addition of potassium tert‐butoxide (t‐BuOK) while the second is based on the use of a catalytic amount of an ammonium phenoxide. The latter opens the way for a catalytic and asymmetric version of this Brook/elimination/aldol reaction (BEAR) sequence.magnified image

Alternative Route For Addition

In a development that could revise organic chemistry textbooks, a new catalytic version of alkene dichlorination makes the reaction more versatile. Adding Cl2 to double-bonded carbons to give saturated dichlorinated products is a fundamental reaction taught early in the organic chemistry curriculum. It mostly proceeds in just one way: via an “anti” mechanism, in which Cl+ and Cl− ions attack opposite faces of the double bond. Now, researchers have devised the first catalytic alkene dichlorination that proceeds by the alternative “syn” route, in which two Cl− ions attack the same face of the double bond. This approach provides a direct route to stereoisomers of anti-dichlorination products. Chemists have reported alkene syn-dichlorinations before, using antimony and molybdenum chloride reagents, but these reactions were not catalytic and their applicability was severely restricted, primarily to nonsubstituted alkene substrates. The only other way to get alkene syn-dichlorination products has been to use mu...

Bipyridine-functionalized amphiphilic block copolymers as support materials for the aerobic oxidation of primary alcohols in aqueous media

A micellar catalytic version of the aerobic oxidation of primary alcohols was successfully developed based on core-functionalized polymer nanoparticles.

ChemInform Abstract: TBAI‐Catalyzed Oxidative Synthesis of Benzamides from Acetophenones and Carbinols.

ChemInformVolume 46, Issue 4 Isocyclic Compounds ChemInform Abstract: TBAI-Catalyzed Oxidative Synthesis of Benzamides from Acetophenones and Carbinols. Muhammad Sharif, Muhammad Sharif Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorJianbin Chen, Jianbin Chen Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorPeter Langer, Peter Langer Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorMatthias Beller, Matthias Beller Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorXiao-Feng Wu, Xiao-Feng Wu Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this author Muhammad Sharif, Muhammad Sharif Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorJianbin Chen, Jianbin Chen Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorPeter Langer, Peter Langer Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorMatthias Beller, Matthias Beller Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this authorXiao-Feng Wu, Xiao-Feng Wu Leibniz-Inst. Katal., Univ. Rostock, D-18059 Rostock, GermanySearch for more papers by this author First published: 08 January 2015 https://doi.org/10.1002/chin.201504075Read 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 onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume46, Issue4January, 2015 RelatedInformation

Preparation of 3-sulfonylated 3,3-disubstituted oxindoles by the addition of sulfinate salts to 3-halooxindoles.

An efficient method for the preparation of 3-sulfonylated 3,3-disubstituted oxindole derivatives has been developed. The protocol involves a base-catalyzed addition of sulfinate salts to 3-halooxindoles, affording a wide range of 3-sulfonylated 3,3-disubstituted oxindoles in good to excellent yields under mild conditions. A preliminary trial of asymmetric catalytic version was conducted and gave promising enantioselectivity. The mechanism for the reaction was tentatively explored with the help of mass spectrometric analysis.

N-Boc deprotection and isolation method for water-soluble zwitterionic compounds.

A highly efficient TMSI-mediated deprotection and direct isolation method to obtain zwitterionic compounds from the corresponding N-Boc derivatives has been developed. This method has been demonstrated in the final deprotection/isolation of the β-lactamase inhibitor MK-7655 as a part of its manufacturing process. Further application of this process toward other zwitterionic compounds, such as dipeptides and tripeptides, has been successfully developed. Furthermore, a catalytic version of this transformation has been demonstrated in the presence of BSA or BSTFA.