Synthesis of dimethyl 1,2-dihydroisoquinolines through the reaction of isoquinoline and dimethyl acetylenedicarboxylate in the presence of amides

Synthesis of functionalized 1,2-dihydroisoquinolines via one-pot reactions of isoquinoline, alkyl propiolate, and thiazolidin-2,4-dione

The reactive zwitterionic intermediates, generated from addition of isoquinoline to alkyl propiolates, react with thiazolidin-2,4-dione to afford 3-[1-(2,4-dioxothiazolidin-3-yl)isoquinolin-2(1 H)-yl]acrylates in good yields. Using (Z)-5-arylidenethiazolidine-2,4-diones as the NH-acidic component leads to 3-{1-[( Z)-5-benzylidene-2,4-dioxothiazolidin-3-yl] isoquinolin-2(1 H)-yl}acrylates in moderate to good yields in the absence of any catalysts under mild reaction conditions. The reaction between quinoline, ethyl propiolate, and thiazolidin-2,4-dione leads to ethyl 3-[2-(2,4-dioxothiazolidin-3-yl) quinolin-1(2 H)-yl]acrylate.

Synthesis of Dimethyl 2-{1-[(1-Methylimidazol-2-yl)Sulfanyl]-1H-Isoquinolin-2-yl}but-2-Enedioate and Related Compounds

A good yield in the synthesis of dimethyl 2-{1-[(1-methylimidazol-2-yl)sulfanyl]-1 H-isoquinolin-2-yl}but-2-enedioate and related compounds is described involving the reaction of acetylenic esters and 1-methylimidazole-5-thiol or 1-methyltetrazole-5-thiol as SH-acids in the presence of isoquinoline. This one-pot method is simple and effective under mild conditions.

On water: silver-catalyzed domino approach for the synthesis of benzoxazine/oxazine-fused isoquinolines and naphthyridines from o-alkynyl aldehydes

An operationally simple domino approach for the silver-catalyzed synthesis of oxazine/benzoxazine-fused isoquinolines 5a-q and naphthyridines 6a-v by the reaction of o-alkynyl aldehydes 3a-aa with amines having embedded nucleophiles 4a-d under mild reaction condition in water is described. The reaction shows selective C-N bond formation on the more electrophilic alkynyl carbon resulting in the formation of 6-endo-dig cyclized product. The competitive experiments show the viability of an intramolecular nucleophilic attack over an intermolecular attack of the external nucleophile. This methodology accommodates wide functional group variation, which proves to be useful for structural and biological assessment.

Phenanthridine or Isoquinoline are Good Reagents for the Synthesis of Enamino Esters

A new class of enamino esters has been isolated in excellent yields from the 1:1:1 addition reaction between phenanthridine or isoquinoline and activated acetylenic esters in the presence of heterocyclic NH compounds (succinimide, 5-nitroindazole, benzoxazolinone, 6-chlorobenzoxazolinone, carbazole and 3,6-dibromocabazole) or 1,3-dicarbonyl compounds such as 1,3-dimethylbarbituric acid and 1,3-diethyl-2-thiobar- bituric acid.

Tandem electrophilic cyclization-[3+2] cycloaddition-rearrangement reactions of 2-alkynylbenzaldoxime, DMAD, and Br2

Tandem electrophilic cyclization-[3+2] cycloaddition-rearrangement reactions of 2-alkynylbenzaldoximes, DMAD, and bromine are described, which afford the unexpected isoquinoline-based azomethine ylides in good to excellent yields. The products could be further elaborated via palladium-catalyzed cross-coupling reactions to generate highly functionalized isoquinoline-based stable azomethine ylides.