Palladium-catalyzed regio-and diastereoselective C À H functionalization with bromoalkynes and electronically unbiased olefins is reported. The picolinamide directing group enables the formation of putative 5 and 6-exo-metallacycles as intermediates to afford monoalkynylated products in up to 91 % yield in a stereospecific fashion. The systematic study reveals that substrates with a wide range of substituents on the olefin and bromoalkyne coupling partners are tolerated. Chemoselective transformations were demonstrated for the obtained amides, olefins, and alkynes. Conjugated 1,3-enynes are abundant in natural products, [*] B. Supporting information and the ORCID identification number for one of the authors of this article can be found under: https://doi.org/10.1002/anie.202000935. Scheme 2. Prior studies and challenges. TIPS = triisopropylsilyl. Angewandte Chemie Communications Scheme 5. Scope of alkynes. Yields and E/Z ratios are given of isolated products after purification. [a] Determined by 1 H NMR analysis of unpurified reaction mixture. [b] DCE used as solvent. [c] Thermal ellipsoids (100 K) shown at the 30 % probability level. Hydrogen atoms and disorder have been omitted for clarity. Boc = tert-butyloxycarbonyl, TBS = tert-butyldimethylsilyl. Scheme 6. Product derivatizations. TBAF = tetrabutylammonium fluoride. Angewandte Chemie Communications 7821
The first total synthesis of (+)-pedrolide,
a tigliane-derived
diterpenoid featuring an unprecedented 5–5–6–6–3
carbon skeleton, is reported. Key to the approach is the construction
of the bicyclo[2.2.1]heptane core via an intramolecular cyclopentadiene-Diels–Alder
cycloaddition. To this end, a norbornadiene serves as an effective
surrogate for cyclopentadiene, which is unmasked under mild conditions
involving a complex Diels–Alder reaction cascade. In addition,
the synthesis provides a novel approach to a densely functionalized
carane in an efficient and enantioselective manner.
Es wird über eine palladiumkatalysierte regio-und diastereoselektive C-H-Funktionalisierung mit Bromalkinen und elektronisch nicht aktivierten Olefinen berichtet. Die Picolinamid-Gruppe ermçglicht die Bildung von 5-und 6-exo-Metallazyklen als Intermediate, die stereospezifisch monoalkinylierte Produkte in bis zu 91 % Ausbeute liefern. Die systematische Studie zeigt, dass Substrate mit einem breiten Spektrum von Substituenten an den Olefin-und Bromalkin-Kupplungspartnern kompatibel sind. Chemoselektive Transformationen wurden für die erhaltenen Amide, Olefine und Alkine gezeigt.
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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