Transition-metal-free, one-pot, tandem C1-indolylation and N-alkylation of tetrahydroisoquinoline in biodegradable PEG solvent
2020
Gulati, Upasana | Rawat, Srishti | Rawat, D. S. (Diwan S.)
The development of one-pot, multi-component and transition-metal-catalyst free synthetic protocol for N-heterocycles is a green and sustainable approach. The solvent plays a critical role in such catalyst free reactions as it constitutes the major portion of reaction mass and facilitates the stabilization of intermediates for the efficient product formation. We herein report a one-pot and catalyst-free tandem coupling among indole, aldehyde and tetrahydroisoquinoline (THIQ) to afford C1-indolyl-N-alkyl THIQ in biodegradable PEG600 solvent. The present method is found to be highly efficient (42–92%) with broad substrate scope. Further, the E-factor (0.3) of the present catalyst-free system is much better (5–593 times) than the previously reported catalyzed methodologies on virtue of recoverable PEG600 solvent. Overall, these results demonstrate a facile and environmentally benign approach for direct C1-functionalization of THIQ in biodegradable and recoverable solvent making it an industrially relevant methodology in near future.
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