Ruthenium Catalyzed ortho C–H Alkenylation of β‐Carbolines and Isoquinolines Using Terminal Alkynes for the Extended π‐Systems and their Biological Evaluation

Visible Light Driven Metal-Free Photoredox Catalyzed α-benzylation and α-oxygenation of N-substituted tetrahydroisoquinolines: Applications to Synthesis of Natural Products

Herein, visible light mediated organophoto redox catalysed simple and convenient method for the a-benzylation and a-oxygenation of tertiary amines is demonstrated. Synthesis of novel thiophenol based donor acceptor organophotoredox catalysts 4a - 4d were investigated along with commercial catalyst 4-CzIPN ( 4e ). A diverse biologically active a-benzylated tetrahydroisoquinolines and natural products such as (±)-Norlaudanosine, (±)-laudanosine and (±)-xylopinine have been synthesized under the optimized conditions in yields ranging from from 62-91%. Exploitation of synthesized a-benzylated compound using present phtoredox catalyzed conditions gave rise to dehydyrogenative benzylic oxidation product under oxygen atmosphere which is known to display biologically and structurally important properties. Also, various N-protected tertiary amines were found to be suitable for the a-oxygenation reactions using catalyst 4e and resulted in good yields (61-85%).

Ru(II)-Catalyzed regioselective carbene insertion into β-carbolines and isoquinolines

A protocol for carbene insertion into the inert C(sp²)-H bond has been established wherein β-carbolines and isoquinolines are explored as intrinsic directing groups. The Ru(II)-catalyzed strategy employing sulfoxonium ylides as the carbene precursor offers an effective and atom-economical functionalization of substrates of biological interest with only DMSO as the sole by-product. The strategy is scalable to gram scale, and it also showcases a wide range of functional group tolerance. ESI-MS studies assisted in the identification of intermediates and consolidation of a probable mechanistic pathway. Furthermore, investigations revealed that the functionalized molecules not only displayed selective inhibition against cancer cell lines, but also demonstrated promising photophysical properties.