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Please login to access the full content or check if you have access via Variation 3: Sonogashira Reaction under Phase-Transfer Conditions

DOI: 10.1055/sos-SD-043-00304

Griesbeck, A. G.; Soldevilla, A.Science of Synthesis, (200843363.

In order to avoid the formation of symmetrical diyne byproducts (Glaser-type oxidative couplings) in Sonogashira protocols, oxygen and other oxidative agents must be rigorously excluded from the reaction medium. One solution is to use copper-free procedures (see Section Another approach is to use phase-transfer conditions in order to keep the terminal acetylenes at low concentration during the reaction, suppressing the homocoupling routes.[‌74‌] In the example shown in Scheme 22, the terminal acetylene is generated slowly from acetylenic alcohol precursor 40, which, in turn, is formed by a Sonogashira reaction with 2-methylbut-3-yn-2-ol (39) though a conventional protocol. The terminal acetylene intermediate is generated in situ under phase-transfer conditions, thus suppressing its homocoupling.

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