Synthesis of (±)-coerulescine and a formal synthesis of (±)-horsfiline

Iron-Catalyzed Oxidative Coupling of Indoline-2-ones with Aminobenzamides via Dual C-H Functionalization

We describe an unprecedented dual C-H functionalization of indolin-2-one via an oxidative C(sp³)-H/N-H/X-H (X = N, C, S) cross-coupling protocol, which is catalyzed by a simple iron salt under mild and ligand-free conditions and employs air (molecular oxygen) as the terminal oxidant. This method is readily applicable for the construction of tetrasubstituted carbon centers from methylenes and provides a wide variety of spiro N-heterocyclic oxindoles.

Water–DMSO-promoted one-pot synthesis of two new series of dihydropyrrolo[2,3-h]quinolines

Two new series of dihydropyrrolo[2,3-h]quinolines 4 and 6 were synthesized via a three-component reaction synergistically activated by water and DMSO, and new pyrrolo[2,3-h]quinolines 10 can be obtained by oxidation of 4 using Cu(NO₃)₂ as oxidant.

Thieno[2,3-d]pyrimidine as a promising scaffold in medicinal chemistry: Recent advances

Thienopyrimidine scaffold is a fused heterocyclic ring system that structurally can be considered as adenine, the purine base that is found in both DNA and RNA-bioisosteres. Thienopyrimidines exist in three distinct isomeric forms. The current review discusses thieno[2,3-d]pyrimidine as a one of the opulent heterocycles in drug discovery. Its broad range of medical applications such as anticancer, anti-inflammatory, anti-microbial, and CNS protective agents has inspired us to study its structure-activity relationship (SAR), along with its relevant synthetic strategies. The present review briefly summarizes synthetic approaches for the preparation of thieno[2,3-d]pyrimidine derivatives. In addition, the promising biological activities of this scaffold are also illustrated with explanatory diagrams for their SAR studies.

N,2-Dibromo-6-chloro-3,4-dihydro-2H-benzo[e][1,2,4]thiadiazine-7-sulfonamide 1,1-dioxide: an efficient and homogeneous catalyst for one-pot synthesis of 4H-pyran, pyranopyrazole and pyrazolo[1,2-b]phthalazine derivatives under aqueous media

DCDBTSD was successfully applied in the synthesis of 4H-pyran, pyranopyrazole and pyrazolo[1,2-b]phthalazine derivatives by a one-pot multi-component reaction in water.

Cu(OTf)2 catalyzed three component strategy for the synthesis of thienopyridine containing spirooxindoles and their cytotoxic evaluation

Compound 5v docked in caspase-3 (−10.5 kcal mol⁻¹).

Asymmetric organocatalyzed Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde and the three one-pot sequential synthesis of (-)-horsfiline and (-)-coerulescine

(-)-Horsfiline and (-)-coerulescine were synthesized through three one-pot operations in 33 and 46% overall yield, respectively. Key to the success was the efficient use of a diarylprolinol silyl ether to catalyze the asymmetric Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde. This allowed the all-carbon quaternary, spirocyclic carbon stereocenter to be constructed in good yield with excellent enantioselectivity.

Efficient enantioselective total synthesis of (-)-horsfiline

A new efficient and concise enantioselective synthetic method for (-)-horsfiline is reported. (-)-Horsfiline could be obtained from diphenylmethyl tert-butyl malonate in 9 steps (32%,>99% ee) by using the enantioselective phase-transfer catalytic allylation (91% ee) as the key step. This approach can be applied as a practical route for the large-scale synthesis of spirooxindole natural products, which enables a systematic investigation of their biological activity to be performed.

NiO Nanoparticles: An Efficient Catalyst for the Multicomponent One-Pot Synthesis of Novel Spiro and Condensed Indole Derivatives

An efficient catalytic protocol for the synthesis of novel spiro[indoline-3,4′-pyrano[2,3-c]thiazole]carbonitriles and condensed thiazolo[5′′,4′′:5′,6′]pyrano[4′,3′:3,4]furo[2,3-b]indole derivatives is developed in a one-pot three-component approach involving substituted 1H-indole-2,3-diones, activated methylene reagent, and 2-thioxo-4-thiazolidinone under conventional heating and microwave irradiation. This paper describes the use of NiO nanoparticles as catalyst for the synthesis of novel spiro and condensed indole derivatives by Knoevenagel condensation followed by Michael addition. The advantageous features of this methodology are operational simplicity, high yield processing, and easy handling. The particle size of NiO nanoparticle was determined by XRD. After reaction course, NiO nanoparticles can be recycled and reused without any apparent loss of activity.

Total synthesis of (±)-coerulescine and (±)-horsfiline

Wittig olefination-Claisen rearrangement protocol was applied to obtain 3-allyl oxindole. This oxindole was then converted to (±)-coerulescine and (±)-horsfiline.

Tandem intramolecular photocycloaddition-retro-Mannich fragmentation as a route to spiro[pyrrolidine-3,3'-oxindoles]. Total synthesis of (+/-)-coerulescine, (+/-)-horsfiline, (+/-)-elacomine, and (+/-)-6-deoxyelacomine

Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3'-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient cyclobutane. The tandem intramolecular photocycloaddition-retro-Mannich process, abbreviated as TIPCARM, leads to a spiropyrrolidine which is poised to undergo a second retro-Mannich fragmentation that expels the malonate unit and generates transiently an indolenine. The latter undergoes rearrangement to a beta-carboline, which upon brominative oxidation undergoes further rearrangement to an oxindole. With tryptamine as starting material, the entire sequence leads to the alkaloid (+/-)-coerulescine. Starting from 5-methoxytryptamine, a parallel series affords (+/-)-horsfiline. Modification of the malonylidene unit to include an isobutyl substituent at C3 affords a photosubstrate which also undergoes the TIPCARM process. In this case, a 2'-isobutyl-substituted spiro[indoline-3,3'-pyrrolenine] results. This undergoes stereoselective hydride reduction to give a product with relative orientation at the spiro carbon and the new stereocenter bearing the isobutyl appendage corresponding to that of the alkaloid elacomine. From tryptamine, the sequence paralleling that leading to coerulescine and horsfiline terminates at 6-deoxyelacomine, whereas 6-methoxytryptamine as starting material affords (+/-)-elacomine itself.

Multi-component supramolecular synthesis of spirooxindoles catalyzed by β-cyclodextrin in water

A neutral and efficient one-pot three-component aqueous-phase synthesis is developed for various spirooxindole derivatives from isatin, malononitrile, and 1,3-dicarbonyl compounds in high yields by supramolecular catalysis involving β-cyclodextrin. The β-cyclodextrin can be recovered and reused a number of times without any loss of activity.

DMD Mediated Formal Synthesis of (±)-Coerulescine

A highly efficient method for the formal synthesis of the natural product (±)-coerulescine 1 from tetrahydro-β-carboline 3, mediated by dimethyldioxirane (DMD), is described. Compound 15, the N9-demethylated precursor of 1, was prepared from 3 in 4 steps with an overall yield of 95%. The effect of electron withdrawing groups at the N2, N9 atoms of 3 was explored for the oxidative rearrangement step.

Palladium asymmetric allylic alkylation of prochiral nucleophiles: horsfiline

[reaction; see text] The asymmetric synthesis of the oxindole alkaloid horsfiline is described. A palladium-catalyzed asymmetric allylic alkylation (AAA) is used to set the spiro(pyrrolidine-oxindole) stereogenic center.