Synthesis of a representative cis/trans pair of 4,5-disubstituted cyclopentenyllithium reagents

Barth, Wolfgang; Paquette, Leo A.

doi:10.1021/jo00214a008

Cited by 42 publications

(7 citation statements)

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“…As a prelude to the requisite coupling reaction, the readily available 4( R )-( tert -butyldimethylsiloxy)-2-cyclopenten-1-one ( 8 ) was reduced with L-Selectride, and the enolate anion resulting from 1,4-addition was captured with N-phenyltriflimide to afford the enol triflate 9 (Scheme ) gave rise to vinylstannane 10a , brominative substitution , of which delivered 11 in 80% overall yield. Somewhat greater efficiency (94%) was realized when 9 was reacted with a stannyl cyanocuprate to generate 10b in advance of conversion to 11 .…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of Spinosyn A. 1. Enantioselective Construction of a Key Tricyclic Intermediate by a Multiple Configurational Inversion Scheme

Paquette

Gao

et al. 1998

J. Am. Chem. Soc.

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The condensation of (+)-7,7-dimethoxynorbornen-2-one with the cerium reagent derived from enantiopure bromide (+)-11 gives rise to an exo carbinol, which readily undergoes highly stereocontrolled anionic oxy-Cope rearrangement. Conversion of the resulting ketone into 20 proceeds with clean epimerization at C-11 (spinosyn numbering) to properly set the absolute configuration at that site. Reduction of 20 with lithium in liquid ammonia serves to introduce two additional stereogenic centers of the perhydro-as-indacene core. In addition, the protocol makes possible the convenient incorporation of a functionalized two-carbon appendage at C-3 and ultimate generation of a cyclohexene double bond after stereochemical inversion at C-7. This scheme leads to 34, a tricyclic compound subsequently shown to be an advanced precursor to the powerful insecticide spinosyn A.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of Spinosyn A. 1. Enantioselective Construction of a Key Tricyclic Intermediate by a Multiple Configurational Inversion Scheme

Paquette

Gao

et al. 1998

J. Am. Chem. Soc.

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“…The diastereoselective hydrogenation of α,β‐unsaturated ketones is a scarcely treated subject in the chemical literature; most publications focus on chemo‐ and regioselectivity of the hydrogenation,7 and to the best of our knowledge, all published transformations have only been carried out in batch format. Conditions developed by Barth and Paquette8 on a similar system (3.3 mol % Rh as 5 % Rh/C, pentane, 330 mol % Na 2 CO 3 ) could be reproduced in batch with 1 (97:3 cis/trans , <4 h, >95 % yield, <5 % alcohol byproduct) and provided a starting point for the further development of the first synthetic step in our sequence.…”

Section: Methodsmentioning

confidence: 95%

The Mechanism of Water Oxidation: From Electrolysis via Homogeneous to Biological Catalysis

et al. 2010

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Striving for new solar fuels, the water oxidation reaction currently is considered to be a bottleneck, hampering progress in the development of applicable technologies for the conversion of light into storable fuels. This review compares and unifies viewpoints on water oxidation from various fields of catalysis research. The first part deals with the thermodynamic efficiency and mechanisms of electrochemical water splitting by metal oxides on electrode surfaces, explaining the recent concept of the potential‐determining step. Subsequently, novel cobalt oxide‐based catalysts for heterogeneous (electro)catalysis are discussed. These may share structural and functional properties with surface oxides, multinuclear molecular catalysts and the catalytic manganese–calcium complex of photosynthetic water oxidation. Recent developments in homogeneous water‐oxidation catalysis are outlined with a focus on the discovery of mononuclear ruthenium (and non‐ruthenium) complexes that efficiently mediate O2 evolution from water. Water oxidation in photosynthesis is the subject of a concise presentation of structure and function of the natural paragon—the manganese–calcium complex in photosystem II—for which ideas concerning redox‐potential leveling, proton removal, and OO bond formation mechanisms are discussed. The last part highlights common themes and unifying concepts.

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“…It was checked that the trans compound was the thermodynamic isomer by treating compound 12 with sodium carbonate, and this experiment yielded compound 15 . It could be noted that the use of sodium carbonate during hydrogenations of unsaturated ketones was first reported by Paquette who have recommended this procedure in order to enhance the syn -stereoselectivity of the hydrogenation of electrophilic olefinic double bonds. However, the substrates studied by Paquette 12 and others 7d,13 were substantially different from the one at hand because they had only one electron-attracting group linked to the ethylenic double bond.…”

Section: Discussionmentioning

confidence: 99%

Enantioselective Synthesis of Conformationally Restricted Analogs of NMDA: cis- and trans-Piperidine-2,3-dicarboxylic Acids and Methylated Derivatives

et al. 1996

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Various enantiopure stereoisomeric cyclic amino diacids belonging to the 2,3-piperidinedicarboxylic acid series were obtained via an aza-annulation reaction between enamino esters and acryloyl, methacryloyl, or crotonyl chloride. Enantioselective syntheses of these conformationnally restricted analogs of N-methyl-d-aspartic acid were realized owing to a chiral induction originated from (2S)-2-phenylglycinol. New information about the mechanism of the aza-annulation process is inferred from AM1 calculations which were performed in order to explain the steroselectivity displayed during the formation of the C-4 stereocenter in compound 4.

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Synthesis of a representative cis/trans pair of 4,5-disubstituted cyclopentenyllithium reagents

Cited by 42 publications

References 0 publications

Total Synthesis of Spinosyn A. 1. Enantioselective Construction of a Key Tricyclic Intermediate by a Multiple Configurational Inversion Scheme

Total Synthesis of Spinosyn A. 1. Enantioselective Construction of a Key Tricyclic Intermediate by a Multiple Configurational Inversion Scheme

The Mechanism of Water Oxidation: From Electrolysis via Homogeneous to Biological Catalysis

Enantioselective Synthesis of Conformationally Restricted Analogs of NMDA: cis- and trans-Piperidine-2,3-dicarboxylic Acids and Methylated Derivatives

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