Efficient synthesis of pentacyclic benzosultam-annulated thiopyranoindoles via domino Knoevenagel / intramolecular hetero-Diels–Alder reactions in water

Diels–Alder Cycloaddition Reactions in Sustainable Media

“…Recently, the domino Knoevenagel/hetero-Diels-Alder reaction of (E)-N-alkyl-2-aryl-N-(2-formylphenyl)ethane-1-sulfonamides 181 with indoline-2-thiones 168 in water has been disclosed by Langer and Kiamehr (Scheme 40) [120]. After 5 h under refluxing conditions, the resulting pentacyclic benzosultam-annulated thiopyranoindole derivatives 182 and 183 were obtained regioselectively in high yields albeit with poor stereoselectivity.…”

Adventures in the Chemistry of Multicomponent and Domino Reactions

“…The reaction of thioxindoles 1 a,b with N ‐(2‐formylphenyl)‐ N ‐alkyl‐(2‐aryl)ethenesulfonamides 4 a – c , prepared by condensation of anthranilic aldehydes with (2‐aryl)ethenesulfonyl chlorides, afforded 6a,7,9,13c‐tetrahydro‐5 H ‐benzo[3′,4′][1,2]‐thiazino[5′,6′:4,5]thiopyrano[2,3‐ b ]indole‐6,6‐dioxides 5 a – f (Scheme 2). [9] The products were formed in very good to excellent yields, but as mixtures of diastereomers A and B . Similarly to the formation of products 3 a – k , diastereomer B was predominantly formed in most cases.…”

“…Domino reactions represent a valuable tool for the synthesis of spirocyclic compounds. [11] The reaction of N-methylglycine (9) with ninhydrin (10 a) and 3-alkylidene-2-oxindoles 8 a-j, available by condensation of the corresponding oxindoles with aldehydes, afforded dispiro[indene-2,2'-pyrrolidine-3',3''-indole]-1,2'',3(1''H)-triones 11 a-j in good to excellent yields (Scheme 4). [12] The formation of the products can be explained by attack of the nitrogen atom of 9 to the central carbonyl group of 10 a and subsequent cyclization to give intermediate A. Extrusion of carbon dioxide afforded nitrogen ylide B which subsequently underwent [3 + 2] cycloaddition with the exocyclic double bond of 8 a-j via transition state C. The products, which contain two asymmetric carbon atoms, were formed with excellent 1,2-diastereoselectivity.…”

Construction of Indole‐Fused Heterocycles Starting from 2‐Thioxoindolines, Iminoindolines, and Their Derivatives

“…[27] Kiamehrn and Langer also found that pentacyclic benzosultam-annulated thiopyranoindoles 64 and 64' can be easily formed by the reaction of indoline-2-thiones 58 and (E)-N-alkyl-2-aryl-N-(2-formylphenyl) ethene-1sulfonamides 63 (Scheme 19c). [28] In addition, Majumdar and co-workers reported a one-pot, three-component reaction to generate spirooxindole-annulated thiopyran derivatives 67 through Knoevenagel condensation and Michael addition cascade. This reaction could be completed in a short time without any catalyst, and it could furnish the spirooxindole-annulated thiopyran compounds in excellent yields (Scheme 20a).…”

“…For example, Moghaddam and colleagues used 2‐formylphenyl ( E )‐2‐phenylethenyl sulfonates 61 to react with 58 and obtained thiopyranoindole‐annulated benzo‐δ‐sultones 62 and 62’ (Scheme 19b) [27] . Kiamehrn and Langer also found that pentacyclic benzosultam‐annulated thiopyranoindoles 64 and 64’ can be easily formed by the reaction of indoline‐2‐thiones 58 and ( E )‐ N ‐alkyl‐2‐aryl‐ N ‐(2‐formylphenyl) ethene‐1‐sulfonamides 63 (Scheme 19c) [28] …”