A mild and efficient Pd-catalyzed arylative domino carbocyclization of cyclohexadienone-containing 1,6-enynes is described. The reaction tolerates a variety of functionalized boronic acids to afford a cis-fused bicyclic framework containing an α,β-unsaturated ketone with excellent regio- and diastereoselectivity in good yields. The tandem process proceeds with β-arylation of propargylic ether followed by conjugate addition of a vinyl palladium intermediate and subsequent protonolysis of a palladium enolate.
Rhodium-catalyzed
asymmetric hydrogenation of alkyne-tethered cyclohexadienones
enables highly regio- and enantioselective reductive cyclization to
afford cis-hydrobenzofurans and cis-hydroindoles in high yields. Desymmetrization of 1,3-diyne-tethered
cyclohexadienones was also explored, wherein the intramolecular coordination
of a Rh complex with the cyclohexadienone ring induces exclusive regioselectivity.
Mechanistic studies including hydrogen–deuterium crossover
experiments suggested that hydrogen activation is the rate-determining
step for tandem reductive cyclization. Moreover, this highly practical
and atom-economical transformation has tolerance to many functional
groups with a broad range of substrate scope, allowing further transformations
to expand the structural complexity of the bicyclic scaffolds.
We report herein a scalable synthesis of linear heptapeptide side chain of the depsipeptide natural product teixobactin through solution phase. The synthesis of heptapeptide was achieved through an efficient coupling of suitably protected tripeptide and tetrapeptide comprising of three d-amino acids and four usual l-amino acid subunits.
A metal
free DBU catalyzed synthesis of 1,2,3-triazole-fused dihydrobenzoxazinone
derivatives by tandem β-azidation/[3 + 2] cycloaddition reaction
has been developed under mild conditions. The methodological studies
offer a broad scope and proceed well with a wide range of alkynylated
cyclohexa 2,5-dienones, giving new cis-triazole-fused
tricyclic scaffolds.
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