- Systematic Investigation into the Matsuda-Heck Reaction of α-Methylene Lactones: How Conformational Constraints Direct the β-H-Elimination Step
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α-Methylene-γ-butyrolactone and α-methylene-δ-valerolactone undergo Pd-catalyzed Matsuda-Heck couplings with arene diazonium salts to α-benzyl butenolides or pentenolides, respectively, or to α-benzylidene lactones. The observed regioselectivity is strongly ring size dependent, with six-membered rings giving exclusively α-benzyl pentenolides, whereas the five-membered α-methylene lactone reacts to mixtures of regioisomers with a high proportion of (E)-α-benzylidene-γ-butyrolactones. DFT calculations suggest that the reasons for these differences are not thermodynamic but kinetic in nature. The relative energies of the conformers of the Pd σ-complexes resulting from insertion into the Pd-aryl bond were correlated with the dihedral angles between Pd and endo-β-H. This correlation revealed that in the case of the six-membered lactone an energetically favorable conformer adopts a nearly synperiplanar Pd/endo-β-H arrangement, whereas for the analogous Pd σ-complex of the five-membered lactone the smallest Pd/endo-β-H dihedral angle is observed for a conformer with a comparatively high potential energy. The optimized conditions for Matsuda-Heck arylations of exo-methylene lactones were eventually applied to the synthesis of the natural product anemarcoumarin A.
- Schmidt, Bernd,Wolf, Felix,Ehlert, Christopher
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p. 11235 - 11249
(2016/11/28)
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- Copper-catalyzed intermolecular chloro- and bromotrifluoromethylation of alkenes
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A highly practical copper-catalyzed intermolecular halotrifluoromethylation of alkenes has been developed under mild reaction conditions. A variety of Cl/Br-containing trifluoromethyl derivatives were directly synthesized from a wide range of alkenes, including electron-deficient and unactivated alkenes.
- Fu, Mingyang,Chen, Long,Jiang, Yongpeng,Jiang, Zhong-Xing,Yang, Zhigang
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p. 348 - 351
(2016/02/19)
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- Synthesis of α,β-unsaturated lactams by palladium-catalysed intramolecular carbonylative coupling
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Amino vinyl triflates have been shown to undergo an intramolecular, carbonylative coupling in the presence of a palladium catalyst to afford α,β-unsaturated lactams.
- Crisp, Geoffrey T.,Meyer, Adam G.
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p. 5585 - 5596
(2007/10/02)
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- Palladium-Catalyzed Carbonylation. A New Synthesis of α-Methylene γ-, δ-, and ε-Lactams and -Lactones Including Bicyclic Lactams of Pyrrolizidine and Indolizidine Skeletons
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The insertion of carbon monoxide into vinyl halides bearing the secondary amine or alcohol with a catalytic amount of Pd(OAc)2 and PPh3 was realized to give five-, six-, and seven-membered lactams and lactones carrying α-methylene groups in fairly good yields.Bicyclic heterocycles, pyrrolizidine and indolizidine derivatives, were also synthesized from pyrrolidine and piperidine derivatives possessing vinyl halide groups in the side chain at the 2-position of the ring by means of palladium-catalyzed carbonylation.
- Mori, Miwako,Washioka, Yumiko,Urayama, Takao,Yoshiura, Kagari,Chiba, Katsumi,Ban, Yoshio
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p. 4058 - 4067
(2007/10/02)
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- AMINO ACID DERIVATIVES
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New substituted acyl derivatives of amino acids which have the general formula STR1 are useful as angiotensin converting enzyme inhibitors.
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