Table 2. Substrate scope in the synthesis of β-alkynyl esters (donor alkynes) ^a .

^aReaction conditions: (i) 6a–h : 7a ratio = 1.25–1.75 : 1.0, 3 mol% Pd(OAc)₂/TDMPP, 1.0 M in PhMe at 23 °C for 1–18 h. (ii) 5 mol% Cu(OAc)₂·H₂O/17, (EtO)₂MeSiH (2 equiv.), t-BuOH (2 equiv.), 0.20 M in PhMe at 4 °C for 14–20 h. Yields are of isolated products after chromatography. Enatiomeric excesses were determined by chiral HPLC analysis.

^bResult obtained from a 15 mmol-scale reaction using 1.5 mol% Pd(OAc)₂/TDMPP.

^cResult obtained from a 10 mmol-scale reaction using 2.5 mol% Cu(OAc)₂ mol% Cu(OAc)₂·H₂O/17.

^dThe crude reduction product was treated with TBAF (1 M in THF), and the corresponding terminal alkyne (R₁ = H) was isolated after chromatography.

^eThe ee was determined after conversion of the product into a diastereomeric mixture of amides using (S)-α-methylbenzylamine (>95 : 5 dr observed).