Pharmaceutically and structurally important methanobenzo[7]annulenes were synthesized in very good yields with excellent enantio- and diastereoselectivities through an unprecedented organocatalytic formal [3+2] cycloaddition from readily available 2-alkyl-3-hydroxynaphthalene-1,4-diones and alkyl vinyl ketones.
We investigate L-Tyrosine as an efficient catalyst for the Knoevenagel condensation of arylaldehydes with meldrum’s acid containing cyclic active methylene group in solvent-free condition under grindstone method at room temperature to produce substituted-5-benzylidene-2,2-dimethyl-[1,3]dioxane-4,6-diones 3(a–j).
Pharmaceutically and structurally important methanobenzo[7]annulenes were synthesized in very good yields with excellent enantio-and diastereoselectivities through an unprecedented organocatalytic formal [3+ +2] cycloaddition from readily available 2-alkyl-3-hydroxynaphthalene-1,4diones and alkylv inyl ketones.
Lawsones were transformed into the functionally rich framework of methanodibenzo[a,f]azulenes and methanobenzo[f]azulenes in a single‐ or two‐pot operation through five organocatalytic sequential reactions in very good yields with excellent selectivities. These resultant molecules are basic skeletons of important antibiotics, which highlights the value of this formal intramolecular [3+2]‐cycloaddition as a key protocol.
An ideal stereoselective insertion of in situ generated benzynes into lawsones through domino formal [2+2]‐cycloaddition followed by rearrangement is disclosed. The reaction allowed for the preparation of biologically important benzannulated bicyclo[3.3.0]octanes in good yields and with excellent selectivities by using simple substrates and conditions.
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