- Investigating the nature of palladium chain-walking in the enantioselective redox-relay heck reaction of alkenyl alcohols
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The mechanism of the redox-relay Heck reaction was investigated using deuterium-labeled substrates. Results support a pathway through a low energy palladium-alkyl intermediate that immediately precedes product formation, ruling out a tautomerization mechanism. DFT calculations of the relevant transition structures at the M06/LAN2DZ+f/6-31+G level of theory show that the former pathway is favored by 5.8 kcal/mol. Palladium chain-walking toward the alcohol, following successive β-hydride eliminations and migratory insertions, is also supported in this study. The stereochemistry of deuterium labels is determined, lending support that the catalyst remains bound to the substrate during the relay process and that both cis- and trans-alkenes form from β-hydride elimination. (Chemical equation presented).
- Hilton, Margaret J.,Xu, Li-Ping,Norrby, Per-Ola,Wu, Yun-Dong,Wiest, Olaf,Sigman, Matthew S.
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- Preparation of stereochemically pure E- and Z-alkenoic acids and their methyl esters from bicyclo[n.1.0]alkan-1-ols. Application in the synthesis of insect pheromones
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Oxidative cleavage of exo- and endo-alkyl- and hydroxyalkyl-substituted bicyclo[n.1.0]alkan-1-ols with (diacetoxy-λ3-iodanyl)benzene gave the corresponding methyl alkenoates exclusively with E or Z configuration of the double bond. This reaction was used as the key stage in the syntheses of stereoisomerically pure components of pest insect pheromones: (E)-dodec-9-en-1-yl acetate (European pine shoot moth Rhyacionia buoliana), (Z)-tetradec-11-en-1-yl acetate (European oak leafroller Tortrix viridana), and (3E,8Z,11Z)-tetradeca-3,8,11-trien-1-yl acetate (tomato leafminer Tuta absoluta).
- Zubrytski,Kananovich,Matiushenkov
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p. 813 - 823
(2017/08/02)
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- Palladium- and ruthenium-catalyzed cycloisomerization of enynamides and enynhydrazides: A rapid approach to diverse azacyclic frameworks
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I want to ride my azacycle: The title reaction of enynamides affords a wide diversity of azacycles. The reactions are high-yielding, highly stereoselective, and proceed rapidly under mild reaction conditions. Equivalent transformations using enynhydrazides offer new routes to pyrazole and indazole scaffolds. Boc=tert-butoxycarbonyl, EWG=electron-withdrawing group, Ns=4-nitrobenzenesulfonyl, Ts=4-toluenesulfonyl. Copyright
- Walker, P. Ross,Campbell, Craig D.,Suleman, Abid,Carr, Greg,Anderson, Edward A.
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p. 9139 - 9143
(2013/09/12)
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- Enzymes in organic synthesis. 27: Lipase-catalyzed synthesis of (5R,6S)-6-acetoxyalkan-5-olides - Homologues of the mosquito oviposition attractant pheromone
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Sixteen homologous (5R*,6S*)-6-hydroxyalkan-5-olides rac-5 and their acetoxy derivatives rac-6 were synthesized from the corresponding methyl (Z)-alk-5-enoates 3 by osmium(VIII) oxide catalyzed cis-hydroxylation to the dihydroxy esters rac-4 and hydrolysi
- Henkel,Kunath,Schick
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p. 434 - 440
(2007/10/03)
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