A New Method for the Preparation of 2-Thio Substituted Furans by Methylsulfanylation of γ-Dithiane Carbonyl Compounds
作者:Albert Padwa、Cheryl K. Eidell、John D. Ginn、Michael S. McClure
DOI:10.1021/jo010986a
日期:2002.3.1
a thionium ion from a gamma-dithianyl substituted carbonylcompound followed by cyclization of this reactive intermediate onto the tethered carbonyl group. Two methods for thionium ion generation were explored. One of these involved an acid-catalyzed reaction of beta-ketenedithioacetals, prepared from the condensation of 2,2-bis(methylsulfanyl)acetaldehyde with a variety of ketones. Cyclization followed
Total Synthesis of (±)-Stenine Using the IMDAF Cycloaddition of a 2-Methylthio-5-amido-substituted Furan
作者:John D. Ginn、Albert Padwa
DOI:10.1021/ol025746b
日期:2002.5.1
[reaction: see text]. The intramolecular [4 + 2]-cycloaddition of a 2-methylthio-5-amidofuran was used to create the azepinoindole skeleton present in the Stemona alkaloid stenine. The rearranged cycloadduct was converted to stenine (1) in 11 additional steps via a sequence that features a Crabtree catalyst directed hydrogenation (9-->10), iodolactonization (2-->11), and a Keck allylation (11-->12)
Studies on the Synthesis of (±)-Stenine: A Combined Intramolecular [4 + 2]-Cycloaddition/Rearrangement Cascade
作者:Albert Padwa、John D. Ginn
DOI:10.1021/jo050515e
日期:2005.6.1
prepared via the reaction of dimethyl(methylthio)sulfonium tetrafluoroborate (DMSTF) with β-alkoxy-γ-dithiane lactams. Thermolysis of these furans resulted in an intramolecularDiels−Alderreaction (IMDAF). The resulting oxa-bridge cycloadducts underwent a subsequent 1,2-methylthio shift to form tricyclic lactams in high yield. Furan 9, annealed to an azepine ring, underwent the IMDAF reaction at or below
Synthesis of Azapolycyclic Systems via the Intramolecular [4 + 2] Cycloaddition Chemistry of 2-(Alkylthio)-5-amidofurans
作者:Albert Padwa、John D. Ginn、Scott K. Bur、Cheryl K. Eidell、Stephen M. Lynch
DOI:10.1021/jo0111816
日期:2002.5.1
prepared via the reaction of dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF) with beta-alkoxy-gamma-dithiane amides 13-16 and 27-32 in 40-70% yield. Thermolysis of these furans resulted in an intramolecular Diels-Alder reaction (IMDAF). With the exception of 45 and 46, the oxa-bridged cycloadducts could not be isolated but immediately underwent a 1,2-methylthio shift to form bicyclic lactams in 60-100%
Construction of the pentacyclic ring system of apogeissoschizine
作者:M. -Lluïsa Bennasar、Ester Zulaica、Bilal A. Sufi、Joan Bosch
DOI:10.1016/0040-4020(96)00400-0
日期:1996.6
The synthesis of pentacyclic apogeissoschizine-type compounds is reported. It involves the construction of the seven-membered E ring by addition of the enolate derived from methyl 1-indolepropionate to the γ-position of a pyridinium salt, with subsequent acid-promoted cyclization of the resulting 1,4-dihydropyridine, and the closure of the C ring by cyclization on the indole 3-position in the last