Selective construction of indeno[1,2- b ]phenothiazine and indeno[2,1- c ]phenothiazine via tandem annulation reaction

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.

Selective Construction of Diverse Polycyclic Spirooxindoles via a Three-Component Reaction of Cyclic Mercapto-Substituted β-Enamino Esters, Isatins, and Cyclic 1,3-Diketones

The three-component reaction of alkyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetates, isatins, and 1,3-indanedione (1,3-cyclopentanedione) in ethanol in the presence of acetic acid conveniently afforded spiro[indeno[1,2-b]phenothiazine-6,3'-indolines] or spiro[cyclopenta[b]phenothiazine-4,3'-indolines] in good yields and with high diastereoselectivity. More interestingly, a similar three-component reaction with 4-hydroxychromen-2-one resulted in the unexpected polycyclic spiro[benzo[b]chromeno[3',4':5,6]pyrano[2,3-e][1,4]thiazine-7,3'-indolines] in satisfactory yields. A plausible reaction mechanism was rationally proposed for formation of different kinds of the spiro compounds, and the stereochemistries of the various spiro compounds were clearly elucidated.

Domino Reaction of Aromatic Aldehydes and 1,3-Indanediones for Construction of Bicyclo[2.2.2]octanes and Dibenzo[b,g]indeno[1',2':3,4]fluoreno[1,2-d]oxonines

Triethylamine promoted the pseudo-five-component reaction of aromatic aldehyde with four molecules of 1,3-indanediones in refluxing ethanol to give unique polycyclic bicyclo[2.2.2]octane derivatives containing bridged- and spiro-indanone scaffolds in good yields. The mechanistic studies supported that the reaction included base-catalyzed cyclotrimerization of 1,3-indanedione to give an active cyclic diene and the sequential Diels-Alder reaction with in situ generated 2-arylidene-1,3-indanediones as electron-deficient dienophiles. On the other hand, the pseudo-four-component reaction of salicylaldehyde with 1,3-indanedione afforded the dibenzo[b,g]indeno[1',2':3,4]fluoreno[1,2-d]oxonines in high yields. This reaction clearly demonstrated the high efficiency, molecular convergence, atom-economy, and impressive selectivity of multicomponent reactions.

Annulations involving 2-arylidene-1,3-indanediones: stereoselective synthesis of spiro- and fused scaffolds

Stereoselective annulations of 2-arylidene-1,3-indanediones towards spiro-carbocycles as well as spiro/fused heterocycles based on various cycloadditions and tandem annulations are described.

Construction of Dispiro-Indenone Scaffolds via Domino Cycloaddition Reactions of α,β-Unsaturated Aldimines with 2-Arylidene-1,3-indenediones and 2,2'-(Arylmethylene)bis(1,3-indenediones)

The catalyst-free domino reaction of α,β-unsaturated N-alkyl or N-arylaldimines with two molecules of 2-arylidene-1,3-indanediones in dry acetonitrile resulted in polysubstituted spiro[indene-2,3'-indeno[2',1':5,6]pyrano[2,3-b]pyridines] in moderate to good yields and with high diastereoselectivity. The reaction mechanism included sequential aza/oxa-Diels-Alder reactions via both endo-transition states. On the other hand, the catalyst-free domino reaction of α,β-unsaturated N-arylaldimines with 2,2'-(arylmethylene)bis(1,3-indenediones) afforded the mixed diastereoisomeric dispiro[indene-2,1'-cyclohexane-3',2″-indene] derivatives in satisfactory yields. The reaction mechanism of this formal [3 + 3] cycloaddition was believed to proceed with sequential nucleophilic 1,4-/1,2-additions.

Efficient synthesis of novel cyclic fused-phenothiazines via domino cyclization of 2-(benzo[b][1,4]thiazin-3-ylidene)acetate, aromatic aldehydes and cyclic 1,3-diketones

Novel fused and bridged phenothiazine derivatives were selectively synthesized via an acid-promoted reaction of alkyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetate, aromatic aldehydes and cyclic diketones under different reaction conditions.

Construction of indeno[1,2-a]fluorene via domino reaction of 1,3-indanedione and 3-arylideneindolin-2-ones or chalcones

The base promoted domino reaction of 1,3-indanedione with 3-arylideneindolin-2-ones or chalcones afforded novel polysubstituted indeno[1,2-a]fluorenes.