Metal-free photoinduced alkylative [3 + 2] annulation of terminal alkynes with N-alkyl isoquinolin-2-iums by catalytic isoquinoline-based electron donor–acceptor complex

Abstract

A new, metal-free electron donor-acceptor (EDA) complex photocatalysis strategy for alkylative [3+2] annulation of N-alkyl soquinolin-2-ium salts with common alkynes in ethyl actate/H2O to assemble highly functionalized pyrrolo[2,1-a]isoquinolines is presented....

Electron Donor‐Acceptor (EDA) Complex Enabled C−C Cross‐Coupling Reactions of α‐Amino Radicals

“…The method included the treatment of N-alkyl isoquinolin-2-ium salts 17 a with common alkynes 17 b in the presence of isoquinoline and blue LEDs for the rapid synthesis of highly functionalized pyrrolo[2,1-a]isoquinolines 17 c in good yield (Scheme 17). [87] The developed method worked well for a variety of aryl alkynes (R 1 = aryl, naphthyl, heteroaryl) to give the desired cyclo adducts.…”

Photo-induced 1,2-alkylarylation/cyclization of alkenes, alkyl halides and N-alkylindoles via an EDA-complex

“…However, to realize the designing procedure, we identified three main challenges that needed to be addressed: (1) N -alkylindoles should effectively form an EDA complex upon association with alkyl halides. Indoles can associate with electron acceptor to form an EDA complex with the assistance of base or acid; 17 (2) chemoselectivity between difunctionalization and arene C–H functionalization. 18 The alkyl radicals, which generated by SET process between alkyl halides and N -alkylindoles, should prefer to react with alkenes rather than arenes; (3) chemoselectivity between direct difunctionalization and difunctionalization cyclization reaction.…”

Metal‐Free Electrochemical [3+2] Cycloaddition between α‐Amino Carbonyls and Tosylmethyl Isocyanide en route to Substituted Imidazoles

“…[3] One of the well-documented approaches exploits the cascade reaction between tetrahydroisoquinoline esters and electron-deficient alkenes/alkynes, efficiently affording pyrrolo-isoquinoline derivatives via the generation of transient electrophilic iminium species with the help of metal or photoredox catalysts and external oxidant (Scheme 1a). [4] Apart from that, active methylene isocyanides have been realized as useful starting materials en route to multi-functionalized heterocycles. [5] However, these traditional protocols either require transition metals (e.g Cu and Ag) and external oxidants or prefunctionalized moisture-sensitive synthetic handles that restrict practical applicability and incorporation of proper substitution patterns in the synthesized scaffolds (Scheme 1b and 1c).…”