- An improved synthesis of 5-ethyl-4a-methyl-2-oxo-2,3,4,4a,7,8-hexahydronaphthalene and similar 1,3-dienes using palladium catalyzed cross-coupling methodology
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We report an efficient synthesis of 1,3-dienes from readily available enol triflates and vinyltributyltin using Pd2(dba)3 and triphenylarsine. Our approach allows for the preparation of these systems at room temperature and thus prevents isomerization to other isomeric dienes. The mild reaction conditions are attributed to the rate acceleration of the cross-coupling reaction due to the weak σ-donation of the triphenylarsine ligand on the palladium catalyst.
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- A Cascade Suzuki-Miyaura/Diels-Alder Protocol: Exploring the Bifunctional Utility of Vinyl Bpin
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Cascade reactions are an important strategy in reaction design, allowing streamlining of chemical synthesis. Here we report a cascade Suzuki-Miyaura/Diels-Alder reaction, employing vinyl Bpin as a bifunctional reagent in two distinct roles: as an organoboron nucleo phile for cross-coupling and as a Diels-Alder dienophile. Merging these two reactions enables a rapid and operationally simple synthesis of functionalized carbocycles in good yield. The effect of the organoboron subtype on Diels-Alder regioselectivity was investigated and postsynthetic modifications were carried out on a model substrate. The potential for a complementary Heck/Diels-Alder process was also assessed.
- Cain, David L.,McLaughlin, Calum,Molloy, John J.,Carpenter-Warren, Cameron,Anderson, Niall A.,Watson, Allan J. B.
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supporting information
p. 787 - 791
(2019/04/25)
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- Diels-Alder reactions of masked o-benzoquinones with 1-vinylcyclohexenes: A short and efficient entry to highly functionalized decahydrophenanthrene skeleton
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Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding cycloaddition products, that is, decahydrophenanthrenes along with bicyclo[2.2.2]octenones. In the former case, the MOBs serve as the dienophile, and in the later case, the 1-vinylcyclohexenes act as the dienophile. The obtained bicyclo[2.2.2]octenones could be transformed into the corresponding decahydrophenanthrenes through a Cope rearrangement at 220 °C. Thus, these tandem reactions provide a short and efficient entry to the decahydrophenanthrene skeleton from easily available 2-methoxyphenols. Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding decahydrophenanthrenes and bicyclo[2.2.2]octenones. The obtained bicyclo[2.2.2]octenones could be transformed into decahydrophenanthrenes through a Cope rearrangement at 220 °C. Copyright
- Niu, Guang-Hao,Hou, Chieh-Shen,Chuang, Gary Jing,Wu, Chi-Phi,Liao, Chun-Chen
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p. 3794 - 3801
(2014/06/24)
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- Enantioselective synthesis of (+)-estrone exploiting a hydrogen bond-promoted Diels?Alder reaction
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Starting from Danes diene and methylcyclopentenedione, (+)-estrone is synthesized along the Quinkert?Dane route in 24% total yield. The key step is an enantioselective Diels?Alder reaction promoted by an amidinium catalyst as efficiently as by a traditional Ti-TADDOLate Lewis acid.
- Weimar, Marko,Duerner, Gerd,Bats, Jan W.,Goebel, Michael W.
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supporting information; experimental part
p. 2718 - 2721
(2010/07/17)
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- Formal enantioselective synthesis of (+)-estrone
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(Chemical Equation Presented) A formal total synthesis of (+)-estrone (4% overall yield; ca. 12 steps) could be achieved via the Torgov diene. An asymmetric allylic substitution is the key step for the construction of the chiral quaternary carbon center of a synthetic intermediate which was converted in four steps to the Torgov diene.
- Soorukram, Darunee,Knochel, Paul
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p. 1021 - 1023
(2007/10/03)
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- Copper-catalyzed allylations of zirconocene intermediates generated from o-alkenyl or o-alkynylbenzyl ether derivatives and zirconocene-butene complex
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(Chemical Equation Presented) o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethyl-styrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene-butene complex (Negishi reagent, "Cp 2Zr"), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.
- Ikeuchi, Yutaka,Taguchi, Takeo,Hanzawa, Yuji
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p. 756 - 759
(2007/10/03)
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- Tandem Enyne Metathesis-Diels-Alder Reaction for Construction of Natural Product Frameworks
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Enynes connected through aromatic rings are used as substrates for metathesis reactions. The reactivity of three ruthenium carbene complexes is compared. The resulting 1,3-dienes are suitable precursors of polycyclic structures via a Diels-Alder process.
- Rosillo, Marta,Dominguez, Gema,Casarrubios, Luis,Amador, Ulises,Perez-Castells, Javier
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p. 2084 - 2093
(2007/10/03)
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- Chemical consequences of fluorine substitution. Part 4. Diels-Alder reactions of fluorinated p-benzoquinones with Dane's diene. Synthesis of fluorinated D-homosteroids
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Four fluorinated p-benzoquinones (2) have been reacted with Dane's diene (1) in Diels-Alder reactions and the formed fluorinated D-homosteroids were characterized. The number of products, their stereochemistry and stability depends on the fluorine substitution pattern of the corresponding fluorinated p-benzoquinones. If the p-benzoquinone (2) contains an unfluorinated double bond, this bond reacts faster with diene 1 yielding endo-products selectively. In contrast, [4+2]cycloadditions with 2,6-difluoro (2c) and 2,3,5,6-tetrafluorobenzoquinone (2d) gave the products with exo-orientation of the carbonyl part preferably.
- Essers, Michael,Haufe, Guenter
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p. 2719 - 2728
(2007/10/03)
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- Total synthesis with a chirogenic opening move demonstrated on steroids with estrane or 18a-homoestrane skeleton
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A concept of first choice for the synthesis of the title compounds had been proposed by Dane in the late 1930s. It was soon turned down, because the opening move - a chirogenic Diels-Alder reaction - did not work. With Lewis acids as mediators, however, a successful start has been achieved now. With Ti complexes of chelating ligands (Seebach's TADDOLs (= α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanols)), enantioselective formation of the desired adducts does occur. Efficient total syntheses of 2 and 3a have been accomplished.
- Quinkert,Del Grosso,Doring,Doring,Schenkel,Bauch,Dambacher,Bats,Zimmermann,Durner
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p. 1345 - 1391
(2007/10/02)
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- Synthesis of the Putative Active Metabolites of the Cyclopentaphenanthrenes. Synthesis of the trans-3,4-Dihydro 3,4-Diol and syn-3,4-Diol 1,2-Epoxide Derivatives of the Mutagen 15,16-Dihydrocyclopentaphenanthren-17-one
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The first synthesis of the trans-dihydro diol and syn-diol epoxide derivatives of a biologically active cyclopentaphenanthrene is described.The cyclopentaphenanthrene skeleton is rapidly and efficiently assembled utilizing the Lewis acid-catalyzed Diels-Alder reaction of 1,2-dihydro-7-methoxy-4-vinylnaphthalene (5) with an α-heterosubstituted cyclopentenone, a "cyclopentynone" equivalent.It was found that the Diels-Alder reaction of α-(phenylselenenyl)- (6a) or α-bromocyclopentenone (6b) with 5 in the presence of 1.5 equiv of SnCl4 followed by elimination with hydrogen peroxide or DBU produced the key intermediate 15,16-dihydro-3-methoxycyclopentaphenanthren-17-one (10) in 28percent or 59percent overall yield, respectively.The synthesis of the A-ring metabolites features the use of a unique methoxime protecting group for the 17-ketone.The deprotection of the 17-methoxime group of the highly acid-sensitive 3,4-trans-dihydro 3,4-diol bis(TBDMS) ether 15b was achieved through the use of the low-valent titanium reagent produced upon reduction of TiCl3-3THF by DIBAL-H (51percent).Treatment of bis-(TBDMS) ether 16 with TBAF in THF provided the desired 3,4-trans-dihydro 3,4-diol (3) (83percent), thus achieving the synthesis of 3 in 10 steps in 9.6percent overall yield from 6b.In addition, the bay-region syn-3,4-diol 1,2-epoxide (4a) was also synthesized from 3 in two steps in 59percent overall yield.
- Woski, Stephen A.,Koreeda, Masato
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p. 5736 - 5741
(2007/10/02)
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