- Palladium(0)-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides: A highly diastereoselective synthesis of tetrahydro-1H-cyclopenta [c] furans bearing two quaternary carbon centers
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A new cascade process has been accomplished for the synthesis of tetrahydro-1H-cyclopenta[c]furans through palladium-catalyzed [2 + 2 + 1] cyclization of 1,6-enynes with vinyl bromides. Notably, the key feature of this transformation is the use of vinyl bromides as the C1 building block. Various functionalized tetrahydro-1H-cyclopenta[c]furans bearing two quaternary carbon centers could be obtained in good yields with excellent diastereoselectivities.
- Diao, Yunxia,Zuo, Zhijun,Wang, Hui,Liu, Jingjing,Luan, Xinjun
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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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- Metal-Free Transfer Hydrobromination of C-C Triple Bonds
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A transfer hydrobromination of C-C triple bonds inititated by Br?nsted acids is reported. Hydrogen bromide is released stepwise from a bench-stable cyclohexa-1,4-diene-based surrogate, generating biphenyl and ethylene as waste. A range of vinyl bromides was prepared from terminal and internal, mainly acceptor-substituted alkynes with good functional-group tolerance.
- Chen, Weiqiang,Oestreich, Martin
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supporting information
p. 4531 - 4534
(2019/06/27)
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- Titanium tetraiodide-promoted tandem prins reaction of alkynes with acetals: Synthesis of (Z,Z)-1,5-Diiodo-1,3,5-triarylpenta-1,4-dienes
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In the presence of titanium tetraiodide, a tandem Prins reaction of alkynes proceeded with acetals to give (Z,Z)-1,5diiodo-1,3,5-triarylpenta-1,4-dienes in good yields, where an intriguing reversal of the stereoselectivity was observed among titanium tetr
- Shimizu, Makoto,Okura, Kanako,Arai, Takuya,Hachiya, Iwao
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scheme or table
p. 1052 - 1054
(2011/01/10)
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- A mild synthesis of vinyl halides and gem-dihalides using triphenyl phosphite-halogen-based reagents
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A new application of (PhO)3P-halogen-based reagents to the synthesis of vinyl halides and gem-dihalides is described. Vinyl halides were prepared in good to excellent yields from enolizable ketones, whereas aldehydes afforded the corresponding gem-dihalides. The halogenation proceeded smoothly under mild conditions.
- Spaggiari, Alberto,Vaccari, Daniele,Davoli, Paolo,Torre, Giovanni,Prati, Fabio
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p. 2216 - 2219
(2007/10/03)
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- Regiochemical variation in the electrophilic addition of HBr to 1-phenylprop-1-yne
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The reaction of aryl alkynes with dilute methylene chloride solutions of quaternary ammonium bromide and 20% trifluoroacetic acid produces primarily the syn Markovnikov adducts of hydrogen bromide. At moderate concentrations of the bromide, the principal
- Weiss, Hilton M.,Touchette, Kim M.,Andersen, Frantz,Iskhakov, David
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p. 2148 - 2151
(2007/10/03)
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- The concerted addition of HBr to aryl alkynes; orthogonal pi bond selectivity
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In a weakly acidic solution, the addition of HBr to 1-phenylprop-1-yne produces predominantly the anti-Markovnikov product. In this paper, we consider five possible explanations for this behavior and conclude that the concerted addition is occurring on the acetylenic π bond orthogonal to the extended aromatic π system. The electronic effect of the distal methyl group and the steric hindrance of the coplanar phenyl ring combine to promote bromide attack at the β carbon. Attack on this π bond is insensitive to the electronic effect of meta and para substituents on the ring but is very (sterically) sensitive toward all ortho substituents.
- Weiss, Hilton M.,Touchette, Kim M.,Angell, Sarah,Khan, Jihan
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p. 2152 - 2156
(2007/10/03)
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- Direct preparation of vinyl halides from the corresponding ketones and acetyl halides
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Vinyl chlorides and bromides are obtained in good yield from the corresponding ketones and acetyl halides in the presence of trifluoroacetic or trifluoromethanesulfonic acid. The Z isomer is selectively formed.
- Moughamir, Khadija,Mezgueldi, Bouchra,Atmani, Aziz,Mestdagh, Helene,Rolando, Christian
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- Surface-Mediated Reactions. 4. Hydrohalogenation of Alkynes
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The use of appropriately prepared silica gel and alumina has been found to mediate the addition of hydrogen halides to alkynes.The technique has been rendered even more convenient by the use of various organic and inorganic acid halides that react in the presence of silica gel or alumina to generate hydrogen halides in situ.Treatment in this fashion of 1-propynylbenzene (1), which underwent no reaction in CH2Cl2 solution saturated with HCl, readily afforded the syn addition product, alkenyl chloride (E)-4a.On extended treatment (E)-4a underwent subsequent iaomerization to the thermodynamically more stable Z isomer.Thus either isomer of 4a could be obtained in good yield depending on the reaction conditions.In a similar way bromides (E)- and (Z)-4b were obtained without competing formation of the radical products (E)- and (Z)-5, which occurred in solution.In contrast with solution-phase hydroiodination of alkyne 1, which slowly afforded iodide (E)-4c, surface-mediated addition readily afforded (E)-4c, followed by isomerization to the Z isomer.E ->/- Z equilibration of the alkenyl halides 4 was shown to involve, at last in part, addition-elimination via the gem-dihalides 13.Analogous behavior was exhibited by the phenylalkynes 2 and 3 on surface-mediated hydrohalogenation.Surface-mediated addition of HBr and HI to the internal alkylalkyne 14 afforded principally the anti addition products (Z)-15b,c.Treatment of the terminal alkynes 17 and 22 with (COBr)2 over alumina gave the dibromides 20 and 24/25, respectively, whereas use of acetyl bromide as the HBr precursor afforded the alkenyl bromides 18b and 23.
- Kropp, Paul J.,Crawford, Scott D.
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p. 3102 - 3112
(2007/10/02)
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- SYNTHESIS OF Z-1-BROMO-1-ALKENYLBENZENES
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Z-1-Bromo-1-alkenylbenzenes are synthesized by bromination-desilicobromination of (E-1-phenyl-1-alkenyl)trimethylsilanes.
- Oliva, Alfonso,Molinari, Aurora
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p. 837 - 842
(2007/10/02)
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- BROMOCHLORINATION OF ALKENES WITH DICHLOROBROMATE(1 minus ) ION. II. REGIO- AND STEREOCHEMISTRY FOR THE BROMOCHLORINATION OF 1-PHENYLPROPENES WITH DICHLOROBROMATE(1 minus ) ION.
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The bromochlorinations of 1-phenylpropenes with tetrabutylammonium dichlorobromate(1 minus ) in aprotic solvents (dielectric constants 5-36) were found to be completely anti stereospecific and nonregiospecific, although Markownikoff adduct was mainly form
- Negoro,Ikeda
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p. 2116 - 2120
(2007/10/02)
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