63814-03-9Relevant articles and documents
Hydroamination of Dihapto-Coordinated Benzene and Diene Complexes of Tungsten: Fundamental Studies and the Synthesis of γ-Lycorane
Chordia, Mahendra D.,Dickie, Diane A.,Ericson, Megan N.,Harman, W. Dean,Nedzbala, Hannah S.,Simpson, Spenser R.,Westendorff, Karl S.,Wilson, Katy B.
, (2021)
Reactions are described for complexes of the form WTp(NO)(PMe3)(η2-arene) and various amines, where the arene is benzene or benzene with an electron-withdrawing substituent (CF3, SO2Ph, SO2Me). The arene complex is first protonated to form an η2-arenium species, which then selectively adds the amine. The resulting η2-5-amino-1,3-cyclohexadiene complexes can then be subjected to the same sequence with a second nucleophile to form 3-aminocyclohexene complexes, where up to three stereocenters originate from the arene carbons. Alternatively, 1,3-cyclohexadiene complexes containing an ester group at the 5 position (also prepared from an arene) can be treated with acid followed by an amine to form trisubstituted 3-aminocyclohexenes. When the amine is primary, ring closure can occur to form a cis-fused bicyclic γ-lactam. Highly functionalized cyclohexenes can be liberated from the tungsten through oxidative decomplexation. The potential utility of this methodology is demonstrated in the synthesis of the alkaloid γ-lycorane. An enantioenriched synthesis of a lactam precursor to γ-lycorane is also described. This compound is prepared from an enantioenriched version of the tungsten benzene complex. Regio- and stereochemical assignments for the reported compounds are supported by detailed 2D-NMR analysis and 13 molecular structure determinations (SC-XRD).
Formal total synthesis of (±)-γ-lycorane and (±)-1-deoxylycorine using the [4+2]-cycloaddition/rearrangement cascade of furanyl carbamates
Padwa,Brodney,Lynch
, p. 1716 - 1724 (2001)
The total syntheses of γ-lycorane and (±)-1-deoxylycorine were accomplished using an intramolecular Diels-Alder cycloaddition of a furanyl carbamate as the key step. The initially formed [4+2]-cycloadduct undergoes nitrogen-assisted ring opening followed by deprotonation/reprotonation of the resulting zwitterion to give a rearranged hexahydroindolinone. The stereochemical outcome of the IMDAF cycloaddition has the side arm of the tethered alkenyl group oriented syn with respect to the oxygen bridge. The key intermediate used in both syntheses corresponds to hexahydroindolinone 20. Removal of the t-Boc group in 20 followed by reaction with 6-iodobenzo[1,3]dioxole-5-carbonyl chloride afforded enamide 22. Treatment of this compound with Pd(OAc)2 employing the Jeffrey modification of the Heck reaction provided the galanthan tetracycle 24 in good yield. Compound 24 was subsequently converted into (±)-γ-lycorane using a four-step procedure to establish the cis-B,C-ring junction. A radical-based cyclization of the related enamide 33 was used for the synthesis of 1-deoxylycorine. Heating a benzene solution of 33 with AIBN and n-Bu3SnH at reflux gave the tetracyclic compound 38 possessing the requisite trans fusion between rings B and C in good yield. After hydrolysis and oxidation of 38 to 40, an oxidative decarboxylation reaction was used to provide the C2-C3-C12 allylic alcohol unit characteristic of the lycorine alkaloids. The resulting enone was eventually transformed into (±)-1-deoxylycorine via known synthetic intermediates.
Palladium-Catalyzed Stereoselective Aza-Wacker-Heck Cyclization: One-Pot Stepwise Strategy toward Tetracyclic Fused Heterocycles
Chen, Li-Yuan,Chuang, Ta-Hsien,Lai, Chin-Hung,Tang, Rong-Shiow
supporting information, p. 9337 - 9341 (2020/12/21)
Palladium-catalyzed intramolecular tandem cyclization reactions were conducted for the synthesis of densely cis/cis-fused aza-tetracyclic structures. The process involved a palladium(II)-catalyzed aerobic aza-Wacker reaction, followed by a palladium(0)-catalyzed Heck reaction. The effects of the solvent and benzene substitution pattern on the one-pot, two-step cascade reaction were studied systematically, and a probable mechanism was proposed. Strained pentahydrobenzo[f]cyclopenta[hi]indolizin-6-one and racemic γ-lycorane can also be synthesized rapidly using this palladium-catalyzed aza-Wacker-Heck cyclization reaction.
Short Total Synthesis of (±)-γ-Lycorane by a Sequential Intramolecular Acylal Cyclisation (IAC) and Intramolecular Heck Addition Reaction
Monaco, Alessandra,Szulc, Blanka R.,Rao, Zenobia X.,Barniol-Xicota, Marta,Sehailia, Moussa,Borges, Bruno M. A.,Hilton, Stephen T.
, p. 4750 - 4755 (2017/04/14)
An intramolecular acylal cyclisation (IAC) approach to the synthesis of a range of bicyclic heterocycles is reported. As an example of the utility of the IAC reaction, the methodology was applied in a protecting-group-free five-step total synthesis of (±)-γ-lycorane, incorporating a new intramolecular Heck addition reaction to generate the pentacyclic core structure of the natural product in good yield.
