Convenient construction of tetrahydrochromeno[4',3':2,3]indolizino[8,7-b]indoles and tetrahydroindolizino[8,7-b]indoles via one-pot domino reaction

Synthesis of fused bis-indazoles/indazoles via a one-pot sequential strategy

We report here an efficient synthesis of fused bis-indazoles/indazoles via a one-pot sequential strategy starting from o-azido aldehydes and amines. This novel method involves the sequential formation of 2H-indazole followed by a Pd-catalyzed intramolecular cross-dehydrogenative coupling reaction. Overall, this one-pot sequential reaction involved the formation of new five bonds, resulting in the formation of three heterocyclic rings.

Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates

In the presence of tetrabutylammonium bromide (TBAB), the cycloaddition reaction of phenacylmalononitriles with dialkyl but-2-ynedioates in acetonitrile at room temperature resulted in 3,3-dicyano-5-hydroxy-5-arylcyclopent-1-ene-1,2-dicarboxylates in high yields. More importantly, the DABCO-promoted domino reaction of two molecules of each phenacylmalononitrile and dialkyl but-2-ynedioate in acetonitrile at room temperature afforded unique multifunctionalized carboxamide-bridged dicyclopentenes in moderate to good yields and with high diastereoselectivity.

Rh(ii)-catalyzed synthesis of 5H-isochromeno[3,4-b]indolizines from 4-diazoisochroman-3-imines and pyridines

A Rh(ii)-catalyzed (3 + 2) annulation of pyridines with 4-diazoisochroman-3-imines furnished 5H-isochromeno[3,4-b]indolizines with moderate to good yields and complete regioselectivity.

Highly diastereoselective annulation of 2-substituted 3-nitro-2H-chromenes with hemicurcuminoids and curcuminoids via a double and triple Michael reaction cascade

The K2CO3-catalysed double Michael addition of (E)-1,5-diaryl- and 1-alkyl-5-arylpent-4-ene-1,3-diones to 2-trifluoromethyl- and 2-phenyl-substituted 3-nitro-2H-chromenes in dichloromethane at room temperature for 48 h results in 10-aroyl(acyl)-7-aryl-6a-nitro-6,6a,7,8,10,10a-hexahydro-9H-benzo[c]chromen-9-ones in 75-98% yields as individual...

Selective synthesis of multifunctionalized cyclopent-3-ene-1-carboxamides and 2-oxabicyclo[2.2.1]heptane derivatives

Triethylamine promoted cycloaddition reaction of phenacylmalononitrile with o-hydroxychalcones or chalcone o-enolates to selectively give cyclopent-3-ene-1-carboxamides and 2-oxabicyclo[2.2.1]heptanes.

Iodine-Mediated Domino Cyclization for One-Pot Synthesis of Indolizine-Fused Chromones via Metal-Free sp3 C-H Functionalization

An efficient method for the synthesis of new indolizine-fused chromones has been accomplished from ethyl (E)-3-(2-acetylphenoxy)acrylates and pyridines in a "one-pot" manner. Facile operation in open-air, metal-free, and mild conditions renders this protocol particularly practical and attractive. Moreover, this method can simultaneously construct two molecular fragments of chromone and indolizine. Scale-up experiment and the construction of natural products further prove the practicability of this strategy.

Aza-Annulation of 1,2,3,4-Tetrahydro-β-carboline Derived Enaminones and Nitroenamines: Synthesis of Functionalized Indolizino[8,7-b]indoles, Pyrido[1,2-a:3,4-b']diindoles, Indolo[2,3-a]quinolizidine-4-ones and Other Tetrahydro-β-carboline Fused Heterocycles

Aza-annulation of novel 1,2,3,4-tetrahydro-β-carboline derived enaminones and nitroenamines with various 1,2- and 1,3-bis electrophiles, such as oxalyl chloride, maleic anhydride, 1,4-benzoquinone, 3-bromopropionyl chloride, itaconic anhydride, and imines (from formaldehyde and primary amines), has been investigated. These methodologies provide simple one-step pathways for efficient construction of highly functionalized tetrahydro-β-carboline 1,2-fused, five- and six-membered heterocyclic frameworks, such as indolizino[8,7-b]indoles, pyrido[1,2-a:3,4-b']diindoles, indolo[2,3-a]quinolizidines, and pyrimido[1',6':1,2]pyrido[3,4-b]indoles, which are core structures of many naturally occurring indole alkaloids with diverse bioactivity.