Steric Tuning of Silylacetylenes and Chiral Phosphine Ligands for Rhodium-Catalyzed Asymmetric Conjugate Alkynylation of Enones

Abstract

Rhodium-catalyzed asymmetric conjugate alkynylation of α,β-unsaturated ketones giving β-alkynylketones took place in high yields with high enantioselectivity. The reaction was realized by use of (triisopropylsilyl)acetylene combined with (R)-DTBM-segphos as a chiral phosphine ligand, where the sterically bulky substituents on the silicon and phosphorus atoms suppress the alkyne dimerization.

Rhodium‐ and Palladium‐Catalyzed Asymmetric Conjugate Additions

“…The state of the art for asymmetric alkylination methodologies was reviewed in 2009 [204]. Hayashi and coworkers developed three methods to overcome competitive alkyne dimerization in rhodium-catalyzed ECAs of alkynes to enones [205,206]. The first method consisted of the rearrangement of racemic alkynyl-alkenyl alcohols of type 150 (obtained from the 1,2-addition of a silylated alkynyl lithium onto an enone) to the conjugate addition product 153 (Scheme 1.58).…”

Rh-catalyzed asymmetric 1,4-addition reactions to α,β-unsaturated carbonyl and related compounds: an update

“…The stoichiometric reaction of (E)-[2-(hydroxymethyl)phenyl] dimethyl(1-octenyl)silane 336h-w with 1a-c, 335g catalyzed by [Rh(OH)(cod)] 2 in THF at 35°C afforded the respective adduct 337 in satisfactory yield (Table 107). 305 Encouraged by the successful 1,4-addition of the silicon reagents under mild reaction conditions along with recent discovery on the use of chiral diene ligands, [306][307][308][309][310][311][312][313][314] the authors turned their attention to the application of 336 to asymmetric synthesis (Scheme 176).…”

The Enantioselective Addition of Alkyne Nucleophiles to Carbonyl Groups

“…Recently, Hayashi and co-workers developed two strategies for the rhodium-catalyzed asymmetric conjugate addition of alkynes to enones (Scheme 40). cxxxiii,cxxxiv The first strategy featured a rearrangement of racemic alkynyl alkenyl alcohols such as 173 to the conjugate addition product ( 174 ). This rearrangement was proposed to occur by rhodium coordination to the alcohol, and a β-alkyne elimination to form a chiral rhodium complex bound to the alkyne and enone ( 178 ).…”