An operationally straightforward organocatalytic β-azidation of α,β-unsaturated ketones is described. Reaction of the Zhdankin azidoiodane with enones in the presence of a catalytic amount of an amine provides β-azido ketones via the formation of an electron-donor-acceptor complex. The application of this protocol is demonstrated through one-step elaborations leading to the synthesis of unprecedented classes of 1,2,3-triazoles.
We describe the first atropselective Suzuki−Miyaura cross-coupling of β-keto enol triflates to access axially chiral (Z)diarylmethylidene indanones (DAIs). The chemical, physical, and biological properties of DAIs are unknown, despite their being structurally similar to arylidene indanones, primarily due to the lack of racemic or chiral methods. Through this work, we demonstrate a general and efficient protocol for the racemic as well as the atropselective synthesis of (Z)-DAIs. An unusual intramolecular Morita−Baylis−Hillman reaction is utilized for the Z-selective synthesis of β-keto enol triflates.
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* sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.1c01671.Experimental details and characterization data for all new compounds ( 1 H NMR, 13 C NMR) (PDF)Accession CodesCCDC 2057339 and 2057498 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk
A rapid and straightforward synthesis of a novel series of furo[2,3-d]tropones (or cyclohepta[b]furan-6-ones) has been developed starting from readily and commercially available materials. Directed α-lithiation of furan-3-carboxaldehydes and subsequent reaction with a variety of aldehydes efficiently provide, in one step, access to 3-formyl-2-furylcarbinols, which are otherwise only accessible with difficulty. The 3-formyl-2-furylcarbinols are further elaborated in two steps to the synthesis of furo[2,3-d]tropones in good yields via sequential bismuth(III)chloride-catalyzed furfurylation and an unusual base promoted cyclization strategy. Thus, diverse polysubstituted furotropones and benzofurotropones can be rapidly assembled. This methodology thereby offers a potential approach for the synthesis of several bioactive natural products containing cyclohepta[b]furan core and also for the buildup of complex molecular architectures through higher order cycloaddition reactions of tropones. Further, the new chromophores have been found to possess promising fluorescence properties. Selective fluorogenic sensing behavior of furotropones toward Fe(3+) ions has also been elucidated.
An efficient diversity-oriented approach for the synthesis of previously unknownd i-, tri-, tetra-and spirocyclic pyrano-1,4-dioxinones,p yrano-1,4-dithiinonesa nd pyrano-1,4-oxathiinones from readily available starting compoundsh as been described. Cascade Michaela ddition-cycloacetalisation of acetoxy-, alkoxy-, and aryloxypyranones and 1,2dinucleophiles under mild Lewis acidic conditions providesadirect access to oxygen andsulfur-contain-ing complexh eterocycles.M echanistic aspects of the cascade process were elucidated in light of experimentalf acts.T he methodology described herein shows high promise for the synthesiso fs everal bioactive natural products as well as pharmaceutically important compounds.Pyranone esters 1a-1h and pyranone ethers 14a-14c employedi nt his study were synthesised according to literature Scheme 3. Diastereoselective synthesis of the ABCD-ring carbon skeleton of alliuocide G 7 and other analogousnatural products. [11a]Scheme 4. Large scale reactions to verify the scalability of the presentm ethod.
The first synthesis of dihydrobenzofuranones and benzofurans based on an intramolecular cross-benzoin reaction has been reported. Commercially available 3-furan carboxaldehydes are readily αalkylated to furnish 3-formyl-2-furylcarbinols, which are further elaborated to the synthesis of benzofurans in good yields through sequential bismuth(III) chloride catalysed furfurylation and a novel NHC-promoted intramolecular cross-benzoin condensation reaction.
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