Gröll, B., Schaaf, P., & Schnürch, M. (2017). Improved simplicity and practicability in copper-catalyzed alkynylation of tetrahydroisoquinoline. Monatshefte Für Chemie - Chemical Monthly, 148(1), 91–104. https://doi.org/10.1007/s00706-016-1877-5
Alkynylation reactions of N-protected tetrahydroisoquinolines have been performed using several different protocols of cross dehydrogenative coupling. Initially, a CuCl-catalyzed method was investigated, which worked well with three different N-protecting groups, namely phenyl, PMP, and benzyl and t-BuOOH as oxidant in acetonitrile as solvent. The peroxide could then be replaced by simple air and acetonitrile for water, leading to an overall very environmentally friendly protocol. Finally, a decarboxylative alkynylation protocol starting from alkynoic acids was also developed using again air as oxidant. This avoids the use of gaseous alkynes in the introduction of short-chained alkyne substituents.
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