ol9b02439_si_001.pdf (11.67 MB)
Palladium(0)–Lithium Iodide Cocatalyzed Asymmetric Hydroalkylation of Conjugated Enynes with Pronucleophiles Leading to 1,3-Disubstituted Allenes
journal contribution
posted on 2019-08-23, 17:39 authored by Hirokazu Tsukamoto, Tatsuya Konno, Kazuya Ito, Takayuki DoiAxially chiral 1,3-disubstituted
allenes were synthesized via hydroalkylation
of alkyl- or aryl-substituted conjugated enynes (readily prepared
via a Sonogashira reaction) with pronucleophiles such as dimethyl
malonate under the cocatalysis of DTBM-SEGPHOS-ligated palladium and
lithium iodide. Although the palladium catalyst ligated with (S)-DTBM-SEGPHOS prefers the formation of (R)-1,3-disubstituted allenes, lithium iodide recovers and increases
the intrinsic selectivity producing (S)-allenes by
promoting the isomerization of the exo-alkylidene-π-allylpalladium
intermediate prior to the nucleophilic substitution step.