Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

A straightforward synthetic protocol for the efficient construction of diazepine-containing spiroindolines has been developed and proceeds through a by base-promoted annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates. The reaction mechanism of this formal [4 + 3] annulation includes the in situ generated allylic ylide, nucleophilic substitution, Michael additon, and elimination processes. Additionally, the similar reaction with α-halogenated N-tosylhydrazones also afforded N-tosyl-substituted spiro[indoline-3,5'-[1,2]diazepine] in satisfactory yields. This protocol provides a convenient approach for the assembly of diverse highly functionalized spiro[indoline-3,5'-[1,2]diazepines] and also features a broad substrate scope, simple reaction conditions, and high molecular convergence.

Construction of diverse spirooxindoles via a domino reaction of arylamines, but-2-ynedioates and 3-hydroxy-3-(indol-3-yl)indolin-2-ones

An iodine-promoted domino reaction of arylamines/benzylamines, dialkyl but-2-ynedioates and 3-hydroxy-3-(indol-3-yl)indolin-2-ones showed very interesting molecular diversity. The reaction in acetonitrile at 65 °C in the presence of 30% mmol I2 resulted in spiro[indoline-3,1'-pyrido[4,3-b]indoles] in satisfactory yields. When anilines without para-substituents were used in the reaction, a direct substitution of the hydroxyl group to 2-(phenylamino)maleate at the para-position of aniline gave chain products in good yields. Additionally, similar reactions with benzylamines not only gave spiro[indoline-3,1'-pyrido[4,3-b]indoles], but also afforded spiro[indoline-3,1'-pyrano[4,3-b]indol]-2-ones in lower yields. A plausible domino annulation mechanism was rationally proposed for the formation of different kinds of polycyclic compounds.

Regioselective and Diastereoselective Construction of Diverse Dispiro-Indanone-Fluorenone-Oxindole Motifs

A convenient synthetic protocol for regioselective and diastereoselective construction of complex dispiro-indanone-fluorenone-oxindole motifs was developed by the base-promoted annulation reaction of bindone and MBH carbonates of isatins by adjusting reaction conditions. DABCO promoted the annulation reaction of bindone and MBH carbonates of isatins in DCM at room temperature, affording dispiro[indene-2,4'-fluorene-1',3″-indoline] derivatives in good yields and with high diastereoselectivity. Triethylamine promoted the annulation reaction of two molecular 1,3-indanediones and MBH esters of isatins in ethanol at elevated temperature and selectively gave dispiro[indene-2,4'-fluorene-3',3″-indolines] in moderate yields. However, triethylamine promoted the annulation reaction of excess 1,3-indanediones and MBH esters of isatins in refluxing ethanol, affording dispiro[indene-2,4'-fluorene-3',3″-indolines] with the Z-isomer as the major product and the E-isomer as the minor product.

Construction of Unique Spiro[dibenzo[a,f]azulene-6,2'-indenes] via Unprecedented Annulation of ortho-C-H Bond of Benzylidene Group

The domino reaction of alkyl and aryl isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C resulted in unique functionalized spiro[dibenzo[a,f]azulene-6,2'-indenes] in good yields, in which the two 2-arylidene-1,3-indanediones acted as different building blocks to construct the polycyclic system. More importantly, the unprecedented anticipation of the ortho-position of benzylidene group to form a novel dibenzo[a,f]azulene ring through a formal [5 + 2] cycloaddition process was first observed. On the other hand, DABCO-promoted reaction of the isocyanides with two molecules of 2-arylidene-1,3-indanediones in acetonitrile at 80 °C afforded functionalized spiro[cyclopenta[a]-indene-2,2'-indene] derivatives.

Synthesis of diverse spiro-imidazo pyridine-indene derivatives via acid-promoted annulation reaction of bindone and heterocyclic ketene aminals

A new multi-component reaction for the synthesis of novel and diverse spiro-imidazo pyridine-indene derivatives named spiro[imidazo[1,2-a]indeno[2,1-e]pyridine-5,1′-indene and indenylidene-1H-spiro[imidazo[1,2-a]pyridine-7,1′-indene was successfully developed by the reaction between heterocyclic ketene aminals (generated from 1,1-bis(methylthio)-2-nitro ethylene and diamine) and [1,2′-biindenylidene]-1′,3,3′-trione (bindone) (in situ generated from self-condensation of 1,3-indandion) by using malononitrile as a promoter or as one of the precursors respectively in the presence of p-TSA as the acid catalyst in EtOH as reaction medium under reflux conditions. Depending on whether the reaction is single-step or two-step, malononitrile can act as a promoter or reactant. The convenient one-pot operation, straightforward isolation without using additional purification methods, and the use of a variety of diamines and cysteamine hydrochloride causing a variety of structural products are attractive aspects of the present approach. The synthesized bindone and final product contains active methylene and this active site can be involved in further reactions to synthesize more complex heterocycles.

Efficient construction of diverse spiro[indoline-3,4'-pyrrolo[3,4-b]pyridines] via [3 + 3] cycloaddition of MBH carbonates of isatins with β-enamino maleimides

An efficient method to construct unique spiro[indoline-3,4'-pyrrolo[3,4-b]pyridines] was successfully developed via a DABCO promoted formal [3 + 3] cycloaddition reaction of MBH carbonates of isatins with β-enamino maleimides in acetonitrile at room temperature. This reaction afforded multifunctionalized spiro[indoline-3,4'-pyrrolo[3,4-b]pyridines] and spiro[dipyrrolo[3,4-b:3',4'-e]pyridine-8,3'-indolines] in good yields and with lower diastereoselectivity. The relative configuration of the two diasteromers of the spiro compounds was clearly elucidated by the determination of eight single crystal structures.

Domino reaction of bindone and 1,3-dipolarophiles for the synthesis of diverse spiro and fused indeno[1,2-a]fluorene-7,12-diones

The base promoted domino reaction of bindone ([1,2'-biindenylidene]-1',3,3'-trione) with common 1,3-dipolarophiles showed interesting molecular diversities, from which the unique spiro and fused indeno[1,2-a]fluorine derivatives were conveniently synthesized in satisfactory yields. In the presence of a base, bindone underwent formal [3 + 3] cycloaddition with satylidene malononitriles to give dispiro[indene-2,4'-fluorene-1',3''-indoline]. It also underwent formal [4 + 2] cycloaddition with 4-arylidene-pyrazol-3-ones to give diastereoisomeric spiro[indeno[1,2-a]fluorene-5,4'-pyrazole]. On the other hand, a triethylamine promoted reaction of three molecules of 1,3-indanediones and isatins in toluene afforded spiro[diindeno[2,1-b:2',1'-d]anthracene-11,3'-indoline] derivatives through the domino [4 + 2] cycloaddition and ring-expansion process.

Convenient construction of polycyclic architectures via multicomponent reaction of amino acids, dialkyl but-2-ynedioates and 2-(o-hydroxyarylidene)-1,3-indanediones

Unique polyheterocyclic compounds were efficiently synthesized by cascade reaction of the in situ generation of a special kind of azomethine ylide, 1,3-dipolar cycloaddition and annulation of phenoxide.

Yb(OTf)3 catalyzed [1,3]-rearrangement of 3-alkenyl oxindoles

A Yb(OTf)₃ catalyzed [1,3]-rearrangement of 3-alkenyl oxindoles was achieved, affording a variety of multifunctional 3-ylideneoxindoles with good yields and Z/E selectivities (64%-89% yield, 78 : 22->99 : 1 Z/E). Importantly, an operationally simple, one-pot sequential catalytic synthesis of 3-ylideneoxindoles was also developed. Additionally, a cross [1,3]-rearrangement experiment and nonracemic transformation were also carried out, which indicated a concerted rearrangement mechanism of this methodology.

Selective Synthesis of Diverse Spiro-oxindole-fluorene Derivatives via a DABCO-Promoted Annulation Reaction of Bindone and 3-Methyleneoxindoles

A DABCO-promoted annulation reaction of bindone ([1,2'-biindenylidene]-1',3,3'-trione) and 3-methyleneoxindoles showed very interesting molecular diversity under different reaction conditions. The base-promoted annulation reaction of bindone and 3-phenacylideneoxindoles in DCM at room temperature afforded spiro[indeno[1,2-a]fluorene-5,3'-indoline] derivatives in good yields and with high diastereoselectivity. However, the similar reaction of 2-(2-oxoindolin-3-ylidene) acetates resulted in Z/E-isomeric spiro[indeno[1,2-a]fluorene-5,3'-indolines] with diastereomeric ratios of 2:1 to 10:1. On the other hand, the DABCO-promoted annulation reaction of bindone and 3-methyleneoxindoles in acetonitrile at different temperatures selectively gave spiro[benzo[5,6]pentaleno[1,6a-b]naphthalene-7,3'-indoline] derivatives and complex dispiro[indoline-3,6'-[4b,6a]ethanoindeno[1,2-a]fluorene-14',3″-indolines] in satisfactory yields.

Molecular diversity of the acid promoted domino reaction of 3-hydroxy-3-(indol-3-yl)indolin-2-ones and cyclic mercapto-substituted β-enamino esters

The acetic acid promoted reaction of 3-hydroxy-3-(indol-3-yl)indolin-2-ones and mercapto-substituted β-enamino esters showed very interesting molecular diversity.