Efficient Synthesis of Complex Oxazatricycles via Three-Component Reaction of Isoquinolinium Salts, Acetone and Cyclic Diketones

Stereoselective synthesis of fused-, spiro- and bridged heterocycles via cyclization of isoquinolinium salts: A recent update

Isoquinoline and its derivatives are ubiquitous in natural alkaloids, synthetic materials and pharmaceuticals with broad spectrum of biological activities. In particular, isoquinolinium salts are important in organic synthesis because they...

Selective synthesis of spirooxindoles via a two-step reaction of N-phenacylpyridinium bromide, 1,3-indanedione and N-alkylisations

The three-component reaction of 1,3-indanedione and N-alkylisatins with two molecular N-phenacylpyridinium salts in dry acetonitrile in the presence of triethylamine resulted in unique functionalized spiro[indoline-3,4'-naphtho[1,2-b]furan] derivatives in good yields, which were successfully converted to spiro[indoline-3,2'-naphthalen]-4'-yl acetate derivatives by acylation with acetyl chloride in methylene dichloride and alkoxy-substituted spiro[benzo[h]chromene-5,3'-indolines] by acid-catalyzed etherification reaction in alcohol. The reaction mechanism involved the sequential cycloaddition of the in situ-generated pyridinium ylide to dipolarophilic enone, ring-opening of 1,3-indanedione, and selective annulation.

Diastereoselective synthesis of spirocyclic isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinolines via cascade double [3 + 2]cycloadditions

The one-pot base-promoted cascade double [3 + 2] cycloaddition reaction of N-cyanomethylisoquinolinium chloride with (E)-3-arylideneindolin-2-ones and (E)-N-hydroxybenzimidoyl chloride afforded novel polycyclic spiro[indoline-3,8'-isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinolines] in good yields and with high diastereoselectivity. When 4-arylidenepyrazol-3-ones, 2-arylidene-1,3-indanediones and arylidenemalononitriles were employed in the reaction, the corresponding spiro[isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline-8,4'-pyrazole], spiro[indene-2,8'-isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline], and isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinoline derivatives were also prepared in good yields and with high diastereoselectivty. The relative configurations of the polycyclic spiro compounds were clearly elucidated by determination of fifteen single crystal structures.

The molecular diversity scope of 4-hydroxycoumarin in the synthesis of heterocyclic compounds via multicomponent reactions

4-Hydroxycoumarins are some of the most versatile heterocyclic scaffolds and are frequently applied in the synthesis of various organic compounds. 4-Hydroxycoumarin-based compounds are important among heterocyclic structures due to their biological and pharmaceutical activities. In this study, we provide an overview on the recent applications of 4-hydroxycoumarin in multicomponent reactions for the synthesis of various heterocyclic compounds during the time period of 2015-2018.

Tandem Double [3 + 2] Cycloaddition Reactions at Both C-1 and C-3 Atoms of N-Cyanomethylisoquinolinium Ylide

The base-promoted cycloaddition reaction of N-cyanomethylisoquinolinium chloride with 2-arylidene-1,3-indanediones in dry tetrahydrofuran resulted in the expected spiro[indene-2,1'-pyrrolo[2,1-a]isoquinoline] derivatives. However, the triethylamine-promoted three-component reaction of N-cyanomethylisoquinolinium chloride, aromatic aldehydes, and two molecules of 1,3-indanediones in acetonitrile afforded unique spiro[benzo[f]imidazo[5,1,2-cd]indolizine-4,2'-indene] derivatives in satisfactory yields through tandem double [3 + 2] cycloaddition reactions.

Formation of diverse polycyclic spirooxindoles via three-component reaction of isoquinolinium salts, isatins and malononitrile

The triethylamine promoted three-component reaction of N-(4-nitrobenzyl), N-ethoxycarbonylmethylisoquinolinium bromide, isatins and malononitrile in ethanol afforded spiro[indoline-3,2′-pyrrolo[2,1-a]isoquinolines] in good yields and with high diastereoselectivity. The similar reaction of N-cyanomethylisoquinolinium chloride mainly gave complex indolo[2″,3″:2′,3′]pyrrolo[3′,4′:4,5]pyrrolo[2,1-a]isoquinoline derivatives. However, the three-component reaction of N-cyanomethylisoquinolinium chloride, isatins and ethyl cyanoacetate mainly resulted in functionalized spiro[indoline-3,8′-pyrido[2′,3′:4,5]pyrrolo[2,1-a]isoquinolines].

Diastereoselective synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes

Diastereospecific synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes.

A [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide

A unique [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide is investigated to afford polycyclic compounds with ten stereogenic centers.