- Photochemical and thermal [2 + 2] cycloaddition to generate the bicyclo[3.2.0]heptane core of bielschowskysin
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A bicyclic core fragment of the marine diterpenoid bielschowskysin has been synthesized. First, a large library of precursors for a photochemical [2 + 2] cycloaddition was prepared and tested, but with limited success. In the end, a thermal [2 + 2] cycloaddition followed by appropriate regio-and stereocontrolled functionalization efficiently gave access to the desired bicyclo[3.2.0]heptane core. An optimized route to this remarkable molecular structure is presented. Copyright
- Farcet, Jean-Baptiste,Himmelbauer, Martin,Mulzer, Johann
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- OXIDATIVE COUPLING OF ARYL BORON REAGENTS WITH SP3-CARBON NUCLEOPHILES, AND AMBIENT DECARBOXYLATIVE ARYLATION OF MALONATE HALF-ESTERS VIA OXIDATIVE CATALYSIS
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Described herein are methods of oxidative coupling of aryl boron reagents with sp3-carbon nucleophiles, and ambient decarboxylative arylation of malonate half-esters via oxidative catalysis.
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Paragraph 0464-0467
(2018/07/29)
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- Synthesis of furo[3,4-c]furans using a rhodium(II)-catalyzed cyclization/Diels - Alder cycloaddition sequence
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A series of 2-alkynyl 2-diazo-3-oxobutanoates, when treated with a catalytic quantity of rhodium(II) acetate, afforded furo[3,4-c]furans in good yield. The reaction proceeds by addition of a rhodium-stablilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid that subsequently cyclizes onto the neighboring carbonyl group to produce the furan ring. These furo[3,4-c]furans react with various dienophiles, furnishing anisole derivatives derived by loss of water from the initially formed Diels - Alder cycloadducts. The Rh(II)-catalyzed cyclization reaction was quite versatile with regard to the nature of the interacting carbonyl group. The methodology was applied to the synthesis of several oxa-polyheterocyclic systems by first generating a 2-alkoxy-substituted furan and then allowing it to undergo a subsequent intramolecular Diels - Alder cycloaddition. Ring opening of the resulting cycloadduct is followed by deprotonation to furnish a rearranged keto lactone. The potential use of this method for the synthesis of the alkaloid strychnine was probed using suitable model diazo compounds. To establish the viability of this approach, the Rh(II)-catalyzed cyclization/cycloaddition sequence of α-diazo amides 64 and 68 were studied. Both compounds underwent the sequential process in good overall yield, leading to novel pentacyclic products. The structural features of the resultant products present numerous opportunities for postcycloaddition manipulations that could be exploited to synthetic advantage.
- Padwa, Albert,Straub, Christopher S.
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p. 227 - 239
(2007/10/03)
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- A new β-keto amide synthesis
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In a modification of the Wierenga-Skulnick β-ketoester synthesis, the dianions of malonic acid mono-amides were condensed with acid chlorides. Acidic workup led to decarboxylation and isolation of the corresponding β-keto amides in good-to-excellent yield
- Chen, Yanping,Sieburth, Scott McN.
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p. 2191 - 2194
(2007/10/03)
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- Facile construction of novel polycyclic ring systems using a metallocarbenoid-induced cyclization of acetylenic diazo carbonyl compounds
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equation presented The Rh(II)-catalyzed reaction of diazo 2-propynyl maolonamic acid ester derivatives produce furo[3,4-c]furans in excellent yield. The methodology was applied to the synthesis of several polyheterocyclic systems by first generating a 2-a
- Padwa, Albert,Straub, Christopher S.
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p. 2093 - 2095
(2007/10/03)
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