Intramolecular direct dehydrohalide coupling promoted by KO(t)Bu: total synthesis of Amaryllidaceae alkaloids anhydrolycorinone and oxoassoanine.

@article{De2012IntramolecularDD,
  title={Intramolecular direct dehydrohalide coupling promoted by KO(t)Bu: total synthesis of Amaryllidaceae alkaloids anhydrolycorinone and oxoassoanine.},
  author={Subhadip De and Santanu Ghosh and Subhajit Bhunia and J. Sheikh and A. Bisai},
  journal={Organic letters},
  year={2012},
  volume={14 17},
  pages={
          4466-9
        }
}
A transition-metal-free intramolecular dehydrohalide coupling via intramolecular homolytic aromatic substitution (HAS) with aryl radicals has been developed in the presence of potassium tert-butoxide and an organic molecule as the catalyst. The methodology has been applied to a concise synthesis of Amaryllidaceae alkaloids viz. oxoassoanine (1b), anhydrolycorinone (1d), and other related structures. Interestingly, the method also works only in the presence of potassium tert-butoxide. 
95 Citations
DMSO/t-BuONa/O2 mediated Aerobic Dehydrogenation of Saturated N-Heterocycles.
TLDR
Aromatic N-Heterocycles such as quinolines, isoquinolines and indolines are synthesized via a sodium tert-butoxide promoted oxidative dehydrogenation of the saturated heterocycles in DMSO solution that has a good functional group tolerance. Expand
DDQ-mediated direct intramolecular-dehydrogenative-coupling (IDC): expeditious approach to the tetracyclic core of ergot alkaloids.
TLDR
An efficient route to 2-oxindoles bearing an all-carbon quaternary center at the pseudobenzylic position has been developed via a DDQ-mediated Intramolecular-Dehydrogenative-Coupling (IDC), which provides a two-step entry to the ergoline structure of ergot alkaloids. Expand
Microwave assisted synthesis of phenanthridinones and dihydrophenanthridines by vasicine/KOtBu promoted intramolecular C-H arylation.
A simple, efficient, rapid and transition metal-free methodology has been developed by utilizing vasicine (a natural product), as a catalyst for the synthesis of phenanthridinones andExpand
Substrates as Electron-Donor Precursors: Synthesis of Naphtho-Fused Oxindoles via Benzannulation of 2-Halobenzaldehydes and Indolin-2-ones.
TLDR
An unusual benzannulation reaction has been realized by integrating intermolecular adol condensation with subsequent intramolercular base-promoted homolytic aromatic substitution to initiate intramolecular radical dehalogenative coupling. Expand
Double Deprotonation of Pyridinols Generates Potent Organic Electron-Donor Initiators for Haloarene-Arene Coupling.
TLDR
The mechanism of transition metal-free couplings of haloarenes with arenes, triggered by the use of alkali metal alkoxides in the presence of an organic additive, is investigated, and evidence is reported for dianions derived from 11 as electron donors to initiate the reaction. Expand
Isopropanol and potassium tert-butoxide promoted intramolecular direct sp2 C–H functionalization: an expedient synthesis of 1,2,3-triazole annulated chromens and quinolones
Abstract A series of 1,2,3-triazole annulated chromen and quinolone derivatives have been synthesized by means of direct sp 2 C–H functionalization in the presence of iso -propanol and potassium tertExpand
An Expedient Synthesis of Carbazoles through Potassium tert‐Butoxide‐Promoted Intramolecular Direct C–H Bond Arylation
Transition metal-free access to carbazoles has been achieved on the basis of base-mediated intramolecular C−C bond formation. Reactions of N-substituted o-halodiarylamines with potassiumExpand
Potassium ethoxide/phenanthroline promoted chemoselective direct C–H arylation of unactivated arenes with aryl iodides
Abstract Simple and cheap potassium ethoxide (EtOK) and a catalytic amount of phenanthroline can efficiently promote the direct C–H arylation of unactivated arenes with aryl iodides at 80 °C. ThisExpand
Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides
Two regiodivergent approaches to intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and amides have been developed, controlled by the reagents employed. With the Brønsted baseExpand
Synthesis of benzimidazoles by potassium tert-butoxide-promoted intermolecular cyclization reaction of 2-iodoanilines with nitriles.
TLDR
The synthesis of benzimidazoles by intermolecular cyclization reaction of 2-iodoanilines with nitriles with Nitriles has been developed without the aid of any transition metals or ligands and just using KOBu(t) as the base. Expand
...
1
2
3
4
5
...

References

SHOWING 1-10 OF 47 REFERENCES
A domino amidation route to indolines and indoles: rapid syntheses of anhydrolycorinone, hippadine, oxoassoanine, and pratosine.
TLDR
The result is a one-step synthesis of indolines which may be oxidized to indoles and the utility of the procedure is illustrated by the two- or three-step syntheses of anhydrolycorinone, hippadine, oxoassoanine, and pratosine. Expand
KO(t)Bu mediated synthesis of phenanthridinones and dibenzoazepinones.
TLDR
Carbon-carbon coupling seems to proceed by the generation of a radical in the amide ring which leads to C-H arylation of aniline and direct access to various biaryl lactams containing six- and seven-membered rings chemoselectively. Expand
Direct dehydrative cross-coupling of tautomerizable heterocycles with alkynes via Pd/Cu-catalyzed phosphonium coupling.
The first chemoselective direct dehydrative cross-coupling of tautomerizable heterocycles with alkynes has been achieved via C-H/C-OH bond activations with direct C(sp(2))-C(sp) bond formation, whichExpand
Synthesis of trisphaeridine and norchelerythrine through palladium-catalyzedaryl–aryl coupling reactions
Total syntheses of trisphaeridine (3) and norchelerythrine (4), fully aromatized phenanthridine and benzo[c]phenanthridine alkaloids, were accomplished via the internal aryl–aryl coupling reactionExpand
Directed ortho metalation approach to C-7-substituted indoles. Suzuki-Miyaura cross coupling and the synthesis of pyrrolophenanthridone alkaloids.
TLDR
In combination with the Suzuki-Miyaura protocol, C-7 aryl (heteroaryl)-substituted indoles 14 and 16 are obtained, including hippadine and pratosine, members of the pyrrolophenanthridone alkaloid family. Expand
Organocatalysis in cross-coupling: DMEDA-catalyzed direct C-H arylation of unactivated benzene.
  • W. Liu, H. Cao, +6 authors A. Lei
  • Chemistry, Medicine
  • Journal of the American Chemical Society
  • 2010
TLDR
A conceptually different approach toward the biaryl syntheses is uncovered by using DMEDA as the catalyst to promote the direct C-H arylation of unactivated benzene in the presence of potassium tert-butoxide. Expand
Potassium t-butoxide alone can promote the biaryl coupling of electron-deficient nitrogen heterocycles and haloarenes.
TLDR
Control experiments support a radical-based mechanism and suggest radical processes may be partially involved in the reported transition-metal-catalyzed arylation reactions employing t-butoxide bases and haloarenes under elevated temperatures or under microwave irradiation. Expand
Potassium tert-butoxide promoted intramolecular arylation via a radical pathway.
Potassium tert-butoxide mediated intramolecular cyclization of aryl ethers, amines, and amides was efficiently performed under microwave irradiation to provide the corresponding products in highExpand
sp3 C-H bond arylation directed by amidine protecting group: alpha-arylation of pyrrolidines and piperidines.
A new ruthenium-catalyzed direct sp3 C-H to C-C bond transformation is disclosed. Specifically, a method for the alpha-arylation of cyclic amines, containing either permanent (pyridine, pyrimidine)Expand
Comparative study of the Kumada, Negishi, Stille, and Suzuki-Miyaura reactions in the synthesis of the indole alkaloids hippadine and pratosine.
TLDR
The total synthesis of hippadine by a tandem metalation/cross-coupling/lactamization strategy was investigated starting from either 7-bromoindole or a 6-halogenated methyl piperonate, and only the Suzuki reaction occurred, affording Hippadine in 67-74% and pratosine in 62% isolated yield. Expand
...
1
2
3
4
5
...