Organotitanium Reagents Research Articles

Enantioselective addition of optically active organotitanium reagents to benzaldehyde

Addition of optically active alkyltitanium (IV) reagents IIb and IIc to benzaldehyde afforded optically active 1-phenylethanol (V) of 37-48% optical purity and 1-phenylpentanol (VI) of 10-24% optical purity. Reagents IIb and IIc were prepared with the use of (1R,2S)-(-)-1-phenyl-1,2-propanediol (III) and (1R,2S)-(+)-1-cyclohexyl-1,2-propanediol (IV) as optically active components. Relations between the enantioselectivity achieved and reaction conditions are discussed.

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen, LXXXII. Zweikernige μ‐Benzylidin‐Komplexe mit Doppelbindung zwischen Rheniumatomen

Multiple Bonds Between Main‐Group Elements and Transition Metals, LXXXII. — Dinuclear p‐Benzylidyne Complexes Having a Double Bond between Rhenium AtomsThe dialkylrhenium(V) complex (η5‐C5Me5)Re(O)(CH2Ph)2 (3) reacts with the organotitanium reagents (η5‐C5H5)TiX3 (X  Cl, Br) to yield the dinuclear rhenium(IV) complexes (η5C5Me5)2 Re2X3(CC6H5) (4a, b). According to a single‐crystal X‐ray diffraction analysis, 4a′ (C5Me4Et in place of C5Me5) represents one of the few known examples of μ‐alkylidyne complexes that have metal‐to‐metal multiple bonds. The molecule of C2 symmetry has a planar four‐membered Re,Cl,Re′,C‐ring geometry and two trans‐oriented sets of ligands. Very small angles at the bridging chloro ligand and alkylidyne carbon atom result from the short metal‐metal distance (double bond).

Diastereoselective Addition of Organometallics to Chiral α-Keto Amides Having trans-2,5-Disubstituted Pyrrolidine

Abstract The nucleophilic addition of organotitanium reagents to α-keto amides derived from (2R,5R)-trans-2,5-bis(t-butyldimethylsiloxymethylsiloxymethyl)pyrrolidine [(R,R)-BTBSP] afforded the corresponding α-hydroxy amides with very high diastereofacial selectivity.

ChemInform Abstract: Organotitanium Reagents in Organic Synthesis

ChemInformVolume 21, Issue 22 Reviews ChemInform Abstract: Organotitanium Reagents in Organic Synthesis M. T. REETZ, M. T. REETZ Fachbereich Chem., Univ. Marburg, D-3550 MarburgSearch for more papers by this author M. T. REETZ, M. T. REETZ Fachbereich Chem., Univ. Marburg, D-3550 MarburgSearch for more papers by this author First published: May 29, 1990 https://doi.org/10.1002/chin.199022330Read 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. Volume21, Issue22May 29, 1990 RelatedInformation

ChemInform Abstract: 1,3‐Anti Asymmetric Induction in Addition of Organotitanium Reagents to β‐Substituted Aldehydes with a Dithioacetal Group.

AbstractThe 2‐formyl‐1,3‐dithianes (I) are treated with various methylmetallic compounds under different conditions to give the hydroxyethyl derivatives (III).

Organotitanium reagents aid aldehyde additions

Organotitanium reagents aid aldehyde additions

1,3-Anti Asymmetric Induction in Addition of Organotitanium Reagents to β-Substituted Aldehydes with a Dithioacetal Group

Abstract β-Substituted aldehydes with a dithioacetal group at α-position realized remarkable 1,3-anti selectivity in addition of organotitanium reagents in acyclic systems.

Book Review: Organotitanium Reagents in Organic Synthesis (Volume 24 in the series Reactivity and Structure, Concepts in Organic Chemistry). By M. T. Reetz

Book Review: Organotitanium Reagents in Organic Synthesis (Volume 24 in the series Reactivity and Structure, Concepts in Organic Chemistry). By M. T. Reetz

ChemInform Abstract: Selective Reaction of Organotitanium Reagents

Chemischer InformationsdienstVolume 17, Issue 14 Reviews ChemInform Abstract: Selective Reaction of Organotitanium Reagents M. T. REETZ, M. T. REETZSearch for more papers by this author M. T. REETZ, M. T. REETZSearch for more papers by this author First published: April 8, 1986 https://doi.org/10.1002/chin.198614379Read 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. Volume17, Issue14April 8, 1986 RelatedInformation

Metalation of 4,5-diphenyl-2-[2-(trimethylstannyl)ethyl]oxazole with titanium tetrachloride. A new carbon-carbon bond forming methodology based on organotitanium reagents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMetalation of 4,5-diphenyl-2-[2-(trimethylstannyl)ethyl]oxazole with titanium tetrachloride. A new carbon-carbon bond forming methodology based on organotitanium reagentsWilliam R. BakerCite this: J. Org. Chem. 1985, 50, 20, 3942–3943Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October 1985https://doi.org/10.1021/jo00220a059RIGHTS & PERMISSIONSArticle Views123Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (287 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Nucleophilic cleavage of acetals using organometallic reagents

A highly chemo- and stereo-selective cleavage of acetals derived from (−)(2 R,4 R)-2,4-pentanediol with organoaluminum and organotitanium reagents has been demonstrated. The reactions proceed under mild conditions with excellent yields and high chemoselectivities to give, after removal of the auxiliary, chiral alcohols of high enantiomeric purities.

Chemoselective addition of organotitanium reagents to carbonyl compounds

The conversion of classical carbanions such as RMgX, RLi, or deprotonated nitriles, sulfones, and carboxylic esters into titanium analogs results which add chemoselectively to carbonyl compounds in the presence of other functional groups. The standard titanating agent is chlorotrisopropoxytitanium (1). Grignard-type reactions and aldol additions are aldehyde-selective in the presence of ketones. Other functional groups such as alkyl and aryl halides, esters, amides as well as nitro and cyano moieties are tolerated. Discrimination between two aldehydes or two ketones is also possible. Replacing alkoxy ligands by methyl groups at titanium increases reactivity dramatically, relatives rates increasing in the series CH3Ti(OCHMe2)3 < (CH3)2Ti-(OCHMe2)2 < (CH3)4Ti. The latter reagent and its zirconium analog methylate sterically hindered and/or enolizable ketones which normally fail to undergo Grignard reactions. The ate complex H2C CHCH2Ti(OCHMe2)4MgCl (63) is aldehyde-selective, while the amino analog H2C CHCH2Ti(NMe2)4MgCl (64) adds selectively to ketones in the presence of aldehydes. Chemoselektive Addition von Organotitan-Agenzien an Carbonyl-Verbindungen Die Uberfuhrung von klassischen Carbanionen wie RMgX, RLi oder deprotonierten Nitrilen, Sulfonen oder Carbonsaureestern in Titan-Analoga ergibt Agenzien, die in Gegenwart von anderen funktionellen Gruppen chemoselektiv an Carbonylverbindungen addieren. Das Standard-Titanierungsagens ist Chlortriisopropoxytitan (1). Grignard-artige Reaktionen sowie Aldoladditionen sind aldehyd-selektiv in Gegenwart von Ketonen. Andere funktionelle Gruppen wie Alkyl- und Arylhalogenide, Ester, Amide sowie Nitro- und Cyanreste werden toleriert. Die Unterscheidung zwischen zwei Aldehyden oder zwei Ketonen ist ebenfalls moglich. Der Ersatz von Alkoxyliganden durch Methylgruppen hat eine drastische Erhohung der Reaktivitat zur Folge, d.h. die relativen Geschwindigkeiten nehmen in folgender Serie zu: CH3Ti(OCHMe2)3 < (CH3)2Ti-(OCHMe2)2 < (CH3)4Ti. Das letztere Agens sowie das Zirkon-Analogon methylieren sterisch gehinderte und/oder enolisierbare Ketone, die normalerweise keine Grignard-Reaktionen eingehen. Der At-Komplex H2C CHCH2Ti(OCHMe2)4 MgCl (63) ist aldehyd-selektiv, wahrend die entsprechende Aminoverbindung H2C CHCH2Ti(NMe2)4MgCl (64) selektiv mit Ketonen in Gegenwart von Aldehyden reagiert.

Stereoselective Addition of Organotitanium Reagents to Carbonyl Compounds

Titanation of alkyllithium or -magnesium compounds using ClTi(OR)3 results in reagents which show markedly increased diastereofacial selectivity (80–90%) in reactions with α-chiral aldehydes or ketones. Titanation is also the method of choice in Grignard-type additions to substituted cyclohexanones; CH3Ti(OCHMe2)3 (6a) adds predominantly from the equatorial direction, while allyltitanium reagents 11b and 12 show axial preference. Crotyltitanium compounds react with carbonyl compounds to afford primarily adducts having anti-configuration, a process which is of particular value in case of ketones (anti/syn ratios up to 99:1). Titanation of (trimethylsilyl)allyllithium (48) with Ti(OCHMe2)4 reverses regioselectivity in reactions with aldehydes and ketones, β-hydroxy silanes 50 being the only observed products. These have anti-configuration and can be converted either into Z- or E-dienes using the Peterson elimination under basic or acidic conditions, respectively. Stereoselektive Addition von Organotitan-Agenzien an Carbonyl-Verbindungen Titanierung von Alkyllithium- oder -magnesium-Verbindungen mittels ClTi(OR)3 ergibt Reagenzien, die eine deutlich erhöhte Diastereoselektivität (80–90%) bei Reaktionen mit α-chiralen Aldehyden oder Ketonen zeigen. Titanierung ist auch die Methode der Wahl im Falle von Grignardartigen Additionen an substituierte Cyclohexanone; CH3Ti(OCHMe2)3 (6a) greift bevorzugt von der äquatorialen Seite an, während die Allyltitan-Reagenzien 11b und 12 hauptsächlich axialen Angriff eingehen. Crotyltitan-Agenzien reagieren mit Carbonyl-Verbindungen unter bevorzugter Bildung von Addukten mit der anti-Konfiguration, eine besonders wertvolle Reaktion im Falle von Ketonen (anti/syn-Verhältnisse bis zu 99:1). Titanierung von (Trimethylsilyl)allyllithium (48) mit Ti(OCHMe2)4 kehrt die Regioselektivität bei Additionen an Aldehyde und Ketone um, denn die einzigen Produkte sind β-Hydroxysilane 50. Sie haben die anti-Konfiguration und können mit Hilfe der Peterson-Eliminierung unter basischen bzw. sauren Bedingungen in Z- oder E-Diene übergeführt werden.

Selective reactions of organotitanium reagents

Abstract

ChemInform Abstract: ENANTIOCONTROLLED SYNTHESIS OF (R)‐3‐SUBSTITUTED CYCLOHEXANONES USING (S)‐2‐(P‐TOLYLSULFINYL)‐2‐CYCLOHEXENONE AND VARIOUS ORGANOMETALLIC REAGENTS IN 2,5‐DIMETHYLTETRAHYDROFURAN

AbstractUnter den jeweils angegebenen Reaktionsbedingungen lassen sich aus den Sulfoxiden (1) entsprechende (R)‐3‐substituierte cyclische Ketone des Typs (III) darstellen.

Nucleophilic cleavages of acetals using organotitanium reagents. A new synthesis of chiral alcohols

A highly chemo- and stereoselective cleavage of acetals derived from (−)-(2R,4R)-2,4-pentanediol with organotitanium reagents has been demonstrated. The reaction proceeds under mild conditions in excellent yield and high chemoselectivity to give, after removal of auxiliary, the chiral alcohols of high enantiopurities. In addition, complexation of chiral acetals and TiCl 4 followed by treatment with n-butyllithium also results in formation of the corresponding n -butylated alcohols with high stereoselectivity.

Enantiocontrolled Synthesis of (R)‐3‐Substituted Cyclohexanones Using (S)‐2‐(p‐Tolylsulfinyl)‐2‐cyclohexenone and Various Organometallic Reagents in 2,5‐Dimethyltetrahydrofuran

AbstractFour different (R)‐3‐substituted cyclohexanones of 65–96% enantiomeric purity have been prepared in 58–84% yields via organometallic conjugate additions to (S)‐2‐(p‐tolylsulfinyl)cyclohexenone in 2,5‐dimethyltetrahydrofuran (DMTHF) as a solvent which allows more effective metal ion chelation by the bidentate β‐ketosulfoxide (and therefore higher asymmetric induction) than does THF. Several recently‐reported organotitanium reagents have been used effectively for the first time as Michael donors.

N‐Methyl‐C‐(trichlortitanio)formimidoylchlorid. Ein effizientes Reagenz zur Homologisierung von Aldehyden und Ketonen zu α‐Hydroxy‐carbonsäureamiden

N‐Methyl‐C‐(trichlorotitanio)formimidoyl Chloride, a Highly Efficient Reagent for Homologations of Aldehydes and Ketones to α‐HydroxycarboxamidesThe known title compound 6 formed by addition of titanium tetrachloride to methyl isocyanide in methylene chloride adds to the carbonyl group of aldehydes and ketones. The adducts 7 are hydrolized to N‐methyl‐α‐hydroxycarboxamides 8 which are (from ketones) or are not branched (from aldehydes) in the α‐position. The yields in this new modification of the Passerini reaction are near 90%, also with readily enolized ketones such as acetone and acetophenone. In contrast to the previously used organotitanium reagents of the type RTiX3, the preparation of the reagent 6 does not require any Li‐, Mg‐ or Zn‐derivative as a precusor.

ChemInform Abstract: ORGANOTITANIUM REAGENTS IN ORGANIC SYNTHESIS. A SIMPLE MEANS TO ADJUST REACTIVITY AND SELECTIVITY OF CARBANIONS

Chemischer InformationsdienstVolume 14, Issue 11 Reviews ChemInform Abstract: ORGANOTITANIUM REAGENTS IN ORGANIC SYNTHESIS. A SIMPLE MEANS TO ADJUST REACTIVITY AND SELECTIVITY OF CARBANIONS M. T. REETZ, M. T. REETZSearch for more papers by this author M. T. REETZ, M. T. REETZSearch for more papers by this author First published: March 15, 1983 https://doi.org/10.1002/chin.198311361AboutPDF 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. Volume14, Issue11March 15, 1983 RelatedInformation

Some recent advances in the use of titanium reagents for organic synthesis

Abstract