Diastereoselective Conjugate Additions to π-Allylmolybdenum Complexes:  A Stereocontrolled Route to 3,4,5-Trisubstituted γ-Butyrolactones

Pearson, Anthony J.; Mesaros, Eugen F.

doi:10.1021/ol020043f

Cited by 26 publications

(3 citation statements)

References 18 publications

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“…Several new methods for the DCA of Grignard reagents to chiral auxiliary-based α,β-unsaturated esters have been developed in recent years, with the majority being based on chiral sugars. – The use of sugar-based auxiliaries was examined by Tadano and co-workers. , It was concluded, based on a systematic investigation of multiple protection patterns (Figure ), that crotonic esters 4 and 6 (Scheme ) provide the best results in terms of both yield and diastereoselectivity due to the distinct steric properties of the substituents at the 2- and 6-positions of the sugar moiety. With these auxiliaries, addition products were obtained with excellent yields (80−95%) and diastereoselectivity (92−96%).…”

Section: Asymmetric Conjugate Addition (Aca) With Grignard Reagentsmentioning

confidence: 99%

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

et al. 2008

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and obtained her degree in Pharmacology in 1999. She has received her Ph.D. degree in Chemistry from the A. N. Nesmeyanov Institute of Organoelement Compounds, Moscow, Russia, with Professor Yuri N. Belokon'. She had a predoctoral stay at the Institute of Organic Chemistry, Polish Academy of Sciences with Dr. C. Grela. After receiving her Ph.D. in 2003, she joined the group of Professor Ben L. Feringa at the University of Groningen as a postdoc. Her work was focused on enantioselective catalysis, mechanistic studies, and total synthesis, in particular using asymmetric conjugate addition. In 2007 she obtained the position of research scientist at Tibotec BVBA, a division of Johnson & Johnson in Belgium. Tim den Hartog was born in 1982, and he studied at the University of Amsterdam, The Netherlands, to obtain his degree in Organic Chemistry in 2005. He is currently performing his graduate studies in the Feringa Group at the University of Groningen in the field of asymmetric catalysis. His research focuses primarily on asymmetric conjugate addition. Koen Geurts was born in 1975, and he studied at the University of Groningen, The Netherlands, and obtained his degree in Organic Chemistry in 2002. He is currently finishing his graduate studies in the Feringa Group at the University of Groningen in the field of asymmetric catalysis. His thesis focuses primarily on asymmetric allylic alkylation. He has recently accepted a position as a chemical development engineer within SABIC Europe.

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Section: Asymmetric Conjugate Addition (Aca) With Grignard Reagentsmentioning

confidence: 99%

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

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“…For example, treatment of 7 , 10 , 11 , and 14 with NaH in DMSO in the presence of a catalytic amount of copper(II) 2-ethylhexanoate7 open to air provided the annulations products 17 – 20 in 83–92% isolated yields (Table 2). In earlier work, Pearson used different non-basic annulative demetalation reagents such as I 2 8 or NOBF 4 9 for related transformations, but exposing our substrates to these reagents (as well as prolonged standing in CDCl 3 ) yielded only the undesired elimination product (i.e., 16 , Scheme 2) through ionization of the carbon nucleophile10 and subsequent proton loss. Mechanistically, we suggest that the reactions of Table 2 proceed through 1-electron oxidation of the stabilized enolate to a radical11 that then reacts with the adjacent η 3 -allylmolybdenum moiety.…”

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A New Reaction Motif: “Homo-S_N2′-Like” Direct Nucleophilic Addition to Neutral η³-Allylmolybdenum Complexes. Total Synthesis of the Antimalarial (+)-Isofebrifugine

Chen

Liebeskind

2009

J. Am. Chem. Soc.

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Charge neutral TpMo(CO) 2 (5-acyloxy-η 3 -pyranyl) and TpMo(CO) 2 (5-acyloxy-η 3 -pyridinyl) scaffolds undergo a novel intermolecular "homo-S N 2′-like" reaction with a variety of carbon nucleophiles. Combined with an annulative demetalation, the homo-S N 2′-like substitution/annulative demetalation sequence rapidly generates 2,7-dioxabicyclo[4.3.0]nonane and 2-aza-7-oxabicyclo [4.3.0]nonane frameworks in good to excellent yields with high enantiopurity. An enantiocontrolled total synthesis of the antimalarial alkaloid (+)-isofebrifugine was achieved utilizing this reaction cascade.Enantiomerically pure, air and moisture-stable TpMo(CO) 2 (η 3 -pyranyl) and TpMo(CO) 2 (η 3 -pyridinyl) complexes, 1 and 2 (Scheme 1), are powerful scaffolds for the enantiocontrolled construction of substituted heterocycles.1 Readily available in multigram quantities, 1m they provide not only new bond construction strategies to access a variety of natural products, but they also constitute platforms from which to explore novel reactivity. A survey of the literature shows that a TpMo(CO) 2 -stabilized carbocation is a requisite intermediate in almost all synthetic transformations of the scaffolds.1a-i,1k,l,1n It was only recently that a new, noncationic pathway taking place through the direct nucleophilic addition of an internal enolate chemLL1@emory.edu. Supporting Information Available: Experimental procedures, synthesis and characterization of all new compounds and X-ray crystallographic studies of 8 (55 pages), scanned copies of 1 H and 13 C NMR spectra of all new compounds (64 pages). This material is available free of charge via the Internet at http://pubs.acs.org. to a terminal π-carbon of neutral 5-oxo-η 3 -pyranyl (and pyridinyl) moiety was reported.1j,1o This synthetically useful 1,5-Michael-like functionalization mode was explained, in part, by the tendency of TpMo(CO) 2 systems to favor 6-coordinate over 7-coordinate structures, 2 and also because the nucleophilic addition generates a characterizable anionic TpMo(CO) 2 intermediate (5 in Scheme 1), which possesses three good π-back-bonding ligands to delocalize the anionic charge: 2 terminal CO's and the η 2 -enone ligand. These observations led us to wonder if the preference for 6-coordinate over 7-coordinate structures alone would be sufficient to enhance a more general nucleophilic addition pathway by which TpMo(CO) 2 (η 3 -allyl) systems that are less-activated than the 5-oxo-η 3 -pyranyl/pyridinyl complexes could be functionalized. Following these considerations, we report herein the first examples of the "homo-S N 2′-like" intermolecular nucleophilic substitution of charge neutral TpMo(CO) 2 (5-acyloxy-η 3 -pyranyl) and TpMo(CO) 2 (5-acyloxy-η 3 -pyridinyl) complexes (3 and 4, Scheme 1). This mechanistically new enantiocontrolled carbon-carbon bond forming reaction occurs enantiospecifically with excellent anti stereoselectivity. NIH Public AccessThe requisite substrates 3a-c, 4a,b (Table 1) are prepared in high yields from the readily available TpMo(CO) 2 (...

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“…Предпочтительность электрофильной атаки по атому углерода или кислорода или азота зависит от природы исходного реагента, электрофила и характера растворителя [2]. Еще одна особенность реакций данного типа с участием α-галогенкарбонильных соединений, которые в органической химии известны как реакция Кневенагеля [3][4][5][6][7] , состоит в том, что в данном случае невозможно выделение промежуточно образующихся продуктов Cалкилирования, поскольку наличие двух карбонильных, нитрильных или нитрогрупп в молекуле придает молекуле намного большую подвижность атому водорода в ней по сравнению с их моноаналогами, и реакция заканчивается образованием замещенных алкенов или образованием циклических соединений.…”

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Interaction of Phosphoryl Substituted Chloroacetic Aldehydes With Ch-Acids

Asadov¹

2018

Chemical Problems

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Поступила в редакцию 12.10.2018 Установлено, что реакции анионов СН-кислот с α-хлоральдегидами протекают исключительно по одному реакционному центрунаиболее электрофильному углеродному атому альдегидной группы. Фосфорилзамещенные хлорацетальдегиды легко конденсируются с производными малоновой кислоты с образованием непредельных фосфорилированных карбоновых кислот. Хлорирование последних является удобным методом синтеза замещенных оксофосфоленов. Ключевые слова: СН-кислота, фосфорилированные α-хлоральдегиды, малоновая кислота, фосфонат, 1,2-оксофосфолен, диэтиловый эфир хлорфосфоновой кислоты, αформилацетилацетон.

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Diastereoselective Conjugate Additions to π-Allylmolybdenum Complexes: A Stereocontrolled Route to 3,4,5-Trisubstituted γ-Butyrolactones

Cited by 26 publications

References 18 publications

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

A New Reaction Motif: “Homo-S_N2′-Like” Direct Nucleophilic Addition to Neutral η³-Allylmolybdenum Complexes. Total Synthesis of the Antimalarial (+)-Isofebrifugine

Interaction of Phosphoryl Substituted Chloroacetic Aldehydes With Ch-Acids

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Diastereoselective Conjugate Additions to π-Allylmolybdenum Complexes: A Stereocontrolled Route to 3,4,5-Trisubstituted γ-Butyrolactones

Cited by 26 publications

References 18 publications

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

Catalytic Asymmetric Conjugate Addition and Allylic Alkylation with Grignard Reagents

A New Reaction Motif: “Homo-SN2′-Like” Direct Nucleophilic Addition to Neutral η3-Allylmolybdenum Complexes. Total Synthesis of the Antimalarial (+)-Isofebrifugine

Interaction of Phosphoryl Substituted Chloroacetic Aldehydes With Ch-Acids

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A New Reaction Motif: “Homo-S_N2′-Like” Direct Nucleophilic Addition to Neutral η³-Allylmolybdenum Complexes. Total Synthesis of the Antimalarial (+)-Isofebrifugine