Enantioselective allylation of selected ortho-substituted benzaldehydes: A comparative study
We report a systematic study of the allylation of ortho-substituted benzaldehydes under catalysis of a Lewis base (N, Ndioxide), a Lewis acid (Keck allylation), and a Bronsted acid. ortho-Halobenzaldehydes were used as the aldehydic substrates, and specia
Hessler, Filip,Betk, Robert,Kadlkov, Aneta,Belle, Roman,Kotora, Martin
p. 7245 - 7252
(2015/01/09)
An unusual access to medium sized cycloalkynes by a new goId(I)-catalysed cycloisomerisation of diynes
A study was conducted to demonstrate efficient cycloisomerization of a series of 1,9- and 1,10-diynes into medium sized cycloalkynes by a gold-catalyzed alkyne-alkyne coupling. The reaction was performed using 4 mol% of gold complex in CD2Cl2 at room temperature and was monitored by using 1H NMR spectroscopy. The reaction of analogous diyne substrate was more rapid and a complete conversion was observed after 40 hours at room temperature. The cycloalkyne was isolated as a solid in 95% yield from which single crystals suitable for X-ray crystal structure determination was obtained. A rapid screening of catalysts and experimental conditions was undertaken to optimize the formation of cycloalkyne. A mechanistic proposal was also introduced for the cycloisomerization of diynes into cycloalkynes on the basis of the experimental observations.
Cycloisomerization of aromatic homo and bis-homopropargylic alcohols via catalytic ru vinylidenes: Formation of benzofurans and isochromenes
Ru-catalyzed cycloisomerizations of aromatic homo- and bis-homopropargylic alcohols effectively afford benzofurans and isochromenes. These processes proved to be chemo- and regioselective (5-, and 6-endo cyclizations) derived from key Ru vinylidene intermediates. The presence of an amine/ammonium base-acid pair is crucial for the catalytic cycle.
Varela-Fernandez, Alejandro,Gonzalez-Rodriguez, Carlos,Varela, Jesus A.,Castedo, Luis,Saa, Carlos
supporting information; experimental part
p. 5350 - 5353
(2009/12/30)
Cobalt-mediated total synthesis of steroids. The A → BCD approach by enediyne cyclization
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Sternberg,Vollhardt
p. 1574 - 1583
(2007/10/02)
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