Synthesis Of Quaternary Carbon Centers Research Articles

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances.

Olefin double-bond functionalization has been established as an excellent strategy for the construction of elaborate molecules. In particular, the hydroalkylation of olefins represents a straightforward strategy for the synthesis of new C(sp3)–C(sp3) bonds, with concomitant formation of challenging quaternary carbon centers. In the last 20 years, numerous hydroalkylation methodologies have emerged that have explored the diverse reactivity patterns of the olefin double bond. This review presents examples of olefins acting as electrophilic partners when coordinated with electrophilic transition-metal complexes or, in more recent approaches, when used as precursors of nucleophilic radical species in metal hydride hydrogen atom transfer reactions. This unique reactivity, combined with the wide availability of olefins as starting materials and the success reported in the construction of all-carbon C(sp3) quaternary centers, makes hydroalkylation reactions an ideal platform for the synthesis of molecules with increased molecular complexity.

ChemInform Abstract: Synthesis of Quaternary Carbon Centers via Hydroformylation.

AbstractThe choice of the catalyst, which serves also as a directing group, is crucial.

Synthesis of Quaternary Carbon Centers via Hydroformylation

The application of hydroformylation to the synthesis of quaternary carbon centers is reported. The synthesis of the highly substituted carbon is achieved by applying a catalytic amount of 1. Ligand 1 serves as a catalytic directing group by covalently and reversibly binding to both the substrate and catalyst. The intramolecular nature of the directing group strategy accelerates the hydroformylation reaction such that the reaction is performed at mild temperatures (35-55 degrees C) and with excellent regioselectivity (b:l > 94:6).

Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions.

Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides--as well as primary ones--to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.

α,α‐Disubstituted Boron Enolates in the Asymmetric Synthesis of Quaternary Carbon Centers.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Alpha,alpha-disubstituted boron enolates in the asymmetric synthesis of quaternary carbon centers.

[reaction: see text] Reduction of alpha,alpha-disubstituted thioglycolate amides with lithium di-tert-butylbiphenylide affords alpha,alpha-disubstituted enolates with high Z/E selectivity. Transmetalation of the enolates with dicyclohexylboron bromide facilitates highly diastereoselective aldol reaction with aromatic and alpha,beta-unsaturated aldehydes.

ChemInform Abstract: Catalytic Asymmetric Synthesis of Quaternary Carbon Centers by Intramolecular Heck Reaction: Synthetic Developments and Mechanistic Studies

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Investigations of Intramolecular Heck Reactions of (E)-α,β-Unsaturated 2-Haloanilides and Analogs To Form Enantioenriched Spirocyclic Products. [J. Am. Chem. Soc. 1998, 120, 6477−6487

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCatalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Investigations of Intramolecular Heck Reactions of (E)-α,β-Unsaturated 2-Haloanilides and Analogs To Form Enantioenriched Spirocyclic Products. [J. Am. Chem. Soc.1998, 120, 6477−6487].Atsuyuki Ashimori, Benoit Bachand, Larry E. Overman, and Cite this: J. Am. Chem. Soc. 2000, 122, 1, 192Publication Date (Web):December 22, 1999Publication History Published online22 December 1999Published inissue 1 January 2000https://doi.org/10.1021/ja995540eCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views902Altmetric-Citations4LEARN 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 (14 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: Catalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Investigations of Intramolecular Heck Reactions of (E)‐α,β‐Unsaturated 2‐Haloanilides and Analogues to Form Enantioenriched Spirocyclic Products.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Catalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Studies of Intramolecular Heck Reactions of (Z)‐α,β‐Unsaturated Anilides and Mechanistic Investigations of Asymmetric Heck Reactions Proceeding via Neutral Intermediates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The synthesis of quaternary carbon centers through cyclialkylations

Treatment of conjugated dienone 1 with a strong Lewis acid at −78 °C produced a hydrophenanthrene with a newly created quaternary carbon. During this transformation the arene moiety becomes a dienone system.

Catalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Investigations of Intramolecular Heck Reactions of (E)-α,β-Unsaturated 2-Haloanilides and Analogues To Form Enantioenriched Spirocyclic Products

The effect of chiral diphosphine structure, method of catalyst generation, reaction solvent, and HI scavenger on the formation of enantioenriched 3,3-disubstituted 2-oxindole 5 from asymmetric Heck cyclization of 4 was studied (eq 1). Depending upon whether the HI scavenger was a silver salt or a basic tertiary amine, either enantiomer of 5 could be formed with good selectivity using the same enantiomer of BINAP. Using Pd−BINAP as catalyst, a variety of enantioenriched 3,3-disubstituted oxindoles, indolines, and dihydrobenzofurans was prepared from (E)-α,β-unsaturated 2-haloaniline substrates (Table 5). With but one exception, cyclizations conducted in the presence of Ag3PO4 or 1,2,2,6,6-pentamethylpiperidine (PMP) afforded opposite enantiomers of the spirocyclic product. Which HI acceptor results in highest enantioselection is substrate dependent. These studies demonstrate, for the first time, that asymmetric Heck reactions of halide substrates can proceed with useful levels of enantioselectivity in the ...

Catalytic Asymmetric Synthesis of Quaternary Carbon Centers. Exploratory Studies of Intramolecular Heck Reactions of (Z)-α,β-Unsaturated Anilides and Mechanistic Investigations of Asymmetric Heck Reactions Proceeding via Neutral Intermediates

Intramolecular Heck reactions of seven (Z)-α,β-unsaturated 2-iodoanilides catalyzed by Pd−BINAP were surveyed using two reaction conditions: (1) silver-promoted cyclizations in the presence of 2 equiv of Ag3PO4 and (2) base-promoted cyclizations in the presence of 4 equiv of 1,2,2,6,6-pentamethylpiperidine (PMP). A comparison of these results with the outcome of the corresponding intramolecular Heck reactions of the E stereoisomers leads to the following conclusions: (1) (E)- and (Z)-α,β-unsaturated 2-iodoanilides give opposite enantiomers of the Heck product when Ag3PO4 is the HI acceptor (cationic pathway); the absolute configuration of the product is independent of alkene geometry when the HI acceptor is PMP (neutral pathway). (2) When the 2-substituent is Me or prim-alkyl, stereoinduction is optimal in PMP-promoted insertions of Z substrates which occur with ee's as high as 97%. (3) When the 2-substituent is large, stereoinduction is optimal in insertions of E substrates carried out in the presence of Ag3PO4. (4) Contributions from the β-alkene substituent are minor. The neutral Heck reaction manifold can be entered from triflate substrates by carrying out the cyclization in the presence of added halide salts. The ability to vary both the alkene geometry and the Heck reaction pathway allows chiral 3,3-disubstituted-2-oxindoles having a wide range of substituents at the quaternary carbon (Me, prim-alkyl, tert-alkyl, and aryl) to be prepared with useful levels of enantioselection (72−97% ee). A number of studies were carried out aimed at clarifying the mechanism of the neutral Heck reaction pathway. Key results are the following: (1) Chiral amplification studies show that the catalyst is monomeric Pd−BINAP. (2) Investigations of monophosphine analogues of BINAP, which were designed to mimic a partially dissociated BINAP chelate, support the conclusion that BINAP is chelated during the enantioselective step. (3) Enantioselectivity is insensitive to solvent polarity. From these data, we propose that the stereochemistry determining step of the neutral pathway occurs during the process in which iodide is displaced by the tethered alkene (Figure 2, 41 → 47 → 45). In light of the variety of pentacoordinate intermediates that could be involved, it is premature to advance a model to rationalize stereoinduction in asymmetric Heck reactions proceeding by the neutral pathway. Nonetheless, the finding that the enantioselective step of asymmetric Heck reactions taking place by the neutral pathway involves five-coordinate intermediates significantly broadens the vista for design of asymmetric ligands for this and related reactions.

ChemInform Abstract: Carbocupration of Cyclopropene. Asymmetric Synthesis of Quaternary Carbon Centers.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Carbocupration of cyclopropene. Asymmetric synthesis of quaternary carbon centers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbocupration of cyclopropene. Asymmetric synthesis of quaternary carbon centersMasahiko Isaka and Eiichi NakamuraCite this: J. Am. Chem. Soc. 1990, 112, 20, 7428–7430Publication Date (Print):September 1, 1990Publication History Published online1 May 2002Published inissue 1 September 1990https://doi.org/10.1021/ja00176a072RIGHTS & PERMISSIONSArticle Views483Altmetric-Citations65LEARN 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 (428 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

ChemInform Abstract: Enantiocontrolled Synthesis of Quaternary Carbon Centers via Anionic Oxy‐Cope Rearrangements: An Efficient Synthesis of (+)‐Dihydromayurone.

ChemInform Abstract: Enantiocontrolled Synthesis of Quaternary Carbon Centers via Anionic Oxy‐Cope Rearrangements: An Efficient Synthesis of (+)‐Dihydromayurone.

ChemInform Abstract: Direct Asymmetric Synthesis of Quaternary Carbon Centers via Addition‐Elimination Process: Nitroolefination of α‐Substituted δ‐Lactones.

AbstractThe reaction of the zinc enolates derived from the lactones (I) and the chiral nitro enamines (II) affords the α,α‐disubstituted lactones (III) with high e.e.

Enantiocontrolled synthesis of quaternary carbon centers via anionic oxy-Cope rearrangement: an efficient synthesis of (+)-dihydromayurone

Synthese de dihydromayurone a partir de β-cyclocitral. L'etape de la synthese est une transposition anionique oxy-Cope de trimethyl-2',2',6' cyclohexene-1'yl-1 butene-3ol-2 en trimethyl-1,3,3 methylene-2 cyclohexanepropanal

Direct asymmetric synthesis of quaternary carbon centers by the addition-elimination process: nitroolefination of .alpha.-substituted .delta.-lactones

Direct asymmetric synthesis of quaternary carbon centers by the addition-elimination process: nitroolefination of .alpha.-substituted .delta.-lactones

ChemInform Abstract: Asymmetric Induction via Addition‐Elimination Process: Nitroolefination of α‐Substituted Lactones.

AbstractA new method for a chiral synthesis of quaternary carbon centers via the addition‐elimination process is described: Reaction of enolates (I) or (IV) with the nitroenamines (II) provides the optically active compounds (III) or (V), respectively.