10 research outputs found
Acid-promoted Cascade Cyclization to Produce Fused-polycyclic Indole Derivatives
An acid-promoted novel cascade cyclization is described. Using 8 equiv of trifluoroacetic acid or a catalytic amount of Lewis acid as the promoter, structurally diverse polycyclic cyclopenta[<i>b</i>]indoles were obtained in moderate to excellent yield. This cascade process was extremely effective for the synthesis of 8-membered ring-fused cyclopenta[<i>b</i>]indole derivatives
Synthetic Study of Pactamycin: Enantioselective Construction of the Pactamycin Core with Five Contiguous Stereocenters
A synthetic
study of pactamycin is described. Enantioselective
construction of the aminocyclopentitol core of pactamycin bearing
five contiguous stereocenters was achieved based on an organocatalytic
asymmetric aziridination of 2-cyclopentene-1-one, a regio- and diastereoselective
1,3-dipolar cycloaddition, and a rhodium-catalyzed C–H amination
reaction
Asymmetric Aziridination of Cyclic Enones Using Chiral Diamine Catalysts and Its Application to the Total Synthesis of (−)-Agelastatin A
The asymmetric aziridination of cyclic enones with <i>N</i>-tosyloxycarbamates, using <i>N</i>-neopentyl 1,2-diphenylethylenediamine as a catalyst, and its application to the formal total synthesis of (−)-agelastatin A, using a one-pot silylation-selenylation procedure and the regioselective aziridine-opening by an azide anion as key steps, are described
Construction of Divergent Fused Heterocycles via an Acid-Promoted Intramolecular <i>ipso</i>-Friedel–Crafts Alkylation of Phenol Derivatives
Two
different cascade cyclization processes were developed using aryl
group-substituted propargyl alcohol derivatives with a <i>p</i>-hydroxybenzylamine unit as common substrates. Using TFA as an acid
promoter, an intramolecular <i>ipso</i>-Friedel–Crafts
alkylation of phenol derivatives, formation of an iminium cation via
a rearomatization-promoted C–C bond cleavage, an aza-Prins
reaction, and a 6-membered ring formation proceeded sequentially,
producing a variety of fused-tricyclic dihydroquinoline derivatives
in 45–99% yield. In addition, a one-pot sequential silver acetate-catalyzed
hydroamination/etherification–acid-promoted skeletal rearrangement
was examined using the same series of substrates, affording fused-tricyclic
indole/benzofuran derivatives in 66–89% yield
Synthetic Study of Pactamycin: Enantioselective Construction of the Pactamycin Core with Five Contiguous Stereocenters
A synthetic
study of pactamycin is described. Enantioselective
construction of the aminocyclopentitol core of pactamycin bearing
five contiguous stereocenters was achieved based on an organocatalytic
asymmetric aziridination of 2-cyclopentene-1-one, a regio- and diastereoselective
1,3-dipolar cycloaddition, and a rhodium-catalyzed C–H amination
reaction
Pd-Catalyzed Cascade Cyclization by Intramolecular Heck Insertion of an Allene–Allylic Amination Sequence: Application to the Synthesis of 3,4-Fused Tricyclic Indoles
A novel Pd-catalyzed cascade cyclization
by intramolecular Heck
insertion of an allene–allylic amination sequence was developed.
Allenes tethered to <i>ortho</i>-iodoaniline derivatives
at the <i>meta</i>-position were reacted with 5–10
mol % of Pd catalyst and 4 equiv of K<sub>2</sub>CO<sub>3</sub> in
DMSO at 90 °C, producing 3,4-fused tricyclic 3-alkylidene indoline
derivatives in moderate to excellent yield. The reaction products
were divergently transformed into three types of 3,4-fused tricyclic
indole derivatives, successfully demonstrating the versatile properties
of the reaction products
Asymmetric Synthesis of Chiral 9,10-Dihydrophenanthrenes Using Pd-Catalyzed Asymmetric Intramolecular Friedel–Crafts Allylic Alkylation of Phenols
We developed a novel asymmetric synthetic method for multisubstituted 9,10-dihydrophenanthrenes based on the Pd-catalyzed asymmetric intramolecular Friedel–Crafts allylic alkylation of phenols, which produces 10-vinyl or 10-isopropenyl chiral 9,10-dihydrophenanthrene derivatives in high yield with up to 94% ee
Asymmetric Synthesis of Chiral 9,10-Dihydrophenanthrenes Using Pd-Catalyzed Asymmetric Intramolecular Friedel–Crafts Allylic Alkylation of Phenols
We developed a novel asymmetric synthetic method for multisubstituted 9,10-dihydrophenanthrenes based on the Pd-catalyzed asymmetric intramolecular Friedel–Crafts allylic alkylation of phenols, which produces 10-vinyl or 10-isopropenyl chiral 9,10-dihydrophenanthrene derivatives in high yield with up to 94% ee
Synthetic Study of Dragmacidin E: Construction of the Core Structure Using Pd-Catalyzed Cascade Cyclization and Rh-Catalyzed Aminoacetoxylation
We
developed a novel synthetic method of the core structure of
dragmacidin E bearing a 7-membered ring-fused bisÂ(indolyl)Âpyrazinone
skeleton. Formation of the 7-membered ring-fused tricyclic indole
skeleton was accomplished using a palladium-catalyzed Heck insertion–allylic
amination cascade. Vicinal difunctionalization of the 7-membered ring
was realized via a rhodium-catalyzed aminoacetoxylation
General Approach to Nitrogen-Bridged Bicyclic Frameworks by Rh-Catalyzed Formal Carbenoid Insertion into an Amide C–N Bond
Various
nitrogen-bridged bicyclic skeletons are found in bioactive
natural products and pharmaceuticals. The development of a new reaction
to construct these molecular frameworks has attracted considerable
attention in synthetic organic chemistry. We developed a novel synthetic
method for obtaining a wide variety of nitrogen-bridged bicyclic compounds
with a catalytic process, Rh-catalyzed formal carbenoid insertion
into an amide C–N bond. Using 0.1–0.4 mol % Rh<sub>2</sub>(NHCO<sup><i>t</i></sup>Bu)<sub>4</sub> catalyst, various
azabicycloÂ[<i>X</i>.<i>Y</i>.<i>Z</i>]Âalkane derivatives were obtained in good to excellent
yield, successfully demonstrating the broad substrate scope of the
developed process. Experimental and computational studies to elucidate
the reaction mechanism revealed that the formal insertion reaction
of a carbenoid into an amide C–N bond proceeded via the formation
of Rh-associated <i>N</i>-ylides, followed by an acyl group-selective
Stevens [1,2]-shift
through a concerted addition/elimination process on the sp<sup>2</sup>-hybridized carbon