Beilstein J. Org. Chem.2019,15, 2747–2752, doi:10.3762/bjoc.15.265
through a 5-exo-dig neighboring group participation (NGP) cyclization and an α-iodointermediate. The work described herein probes the existence of the intermediate through NMR investigations and explores the scope of the hydration process with internal alkynes. The NMR experiments confirm the existence
of the α-iodointermediate, and methodology studies demonstrate that alkyl-capped, asymmetric, internal alkynes undergo a regiospecific hydration, also via the 5-exo-dig NGP pathway.
Keywords: α-iodointermediate; internal alkyne; iodine-mediated hydration; neighboring group participation
group participation for 5-exo-dig cyclization from 3 to 4. It was further hypothesized that the reaction continues through an α-iodointermediate 6, a tautomer of 5, from which deiodination followed by tautomerization of 7 produces the final product 2.
In the studies described herein, NMR experiments
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Graphical Abstract
Scheme 1:
Proposed mechanism for the iodine-mediated hydration of terminal alkynes 1 [15].