Cu(I)-catalyzed one-pot decarboxylation-alkynylation reactions on 1,2,3,4-tetrahydroisoquinolines and one-pot synthesis of triazolyl-1,2,3,4-tetrahydroisoquinolines

- Short chained alkynes can be introduced without the need for gaseous reagents by using the corresponding alkynoic acids.
- Alkynylations with alkynoic acids work in good yields independent of the chain length and protecting group of the substrate.
- A three step cascade of decarboxylation, alkynylation, and click reaction was developed using the same catalyst, namely CuCl.

A facile and efficient method to introduce alkyne groups to the C-1 position of biologically interesting 1,2,3,4-tetrahydroisoquinolines via direct CH-functionalization is reported. Various alkynylated N-substituted 1,2,3,4-tetrahydroisoquinolines could be obtained by using copper(I)-chloride as catalyst, alkynoic acids as alkyne source and t-BuOOH as oxidant, in a one-pot two-step decarboxylation- alkynylation reaction in moderate to high yields. Furthermore, a one-pot protocol of a three-step decarboxylation-alkynylation-1,3-dipolar cycloaddition reaction leading to 1-triazolyl-tetrahydroisoquinolines was developed, a hitherto unknown reaction cascade.

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