Trimethyl Orthoacetate and Ethylene Glycol Mono‐Vinyl Ether as Enolate Surrogates in Enantioselective Iridium‐Catalyzed Allylation

Abstract

Trimethyl orthoacetate and ethylene glycol mono-vinyl ether are employed in iridium-catalyzed enantioselective allylation reactions. The method documented enables their convenient use as surrogates for silyl ketene acetals and silyl enol ethers to prepare γ,δ-unsaturated esters and protected aldehydes with excellent enantioselectivity. The utility of this novel method has been demonstrated by its implementation in a formal enantioselective synthesis of the meroterpenoid (+)-conicol.

Iridium-Catalyzed Enantioselective Allyl–Allyl Cross-Coupling of Racemic Allylic Alcohols with Allylboronates

“…To our knowledge, there is only one case in the literature reported by Jarvo and Barker, which documents the Ir-catalyzed allylation of ketones using allylboronic ester, leading to tertiary homoallylic alcohols . In recent years, iridium-catalyzed allylations have emerged as a versatile tactic for the synthesis of chiral building blocks. , Inspired by the recent seminal and systematic studies by the Carreira group, we proposed that the nucleophilic allylboronic ester would be coupled with an electrophilic, branched, racemic allylic alcohol under the conditions of Carreira’s Ir-(P, olefin) catalyst system. This would offer an alternative to the known allyl–allyl cross-coupling reactions.…”

Morpholine Ketene Aminal as Amide Enolate Surrogate in Iridium‐Catalyzed Asymmetric Allylic Alkylation

“…In contrast to our earlier work with enolate surrogates, in which zinc‐based Lewis acids were optimal promoters for the activation of allylic carbonates in asymmetric allylic alkylation reactions, a screening of various Lewis acids failed to yield improved outcomes (Table , entries 4–6) . Additionally, some decomposition of the nucleophile was evidenced by the isolation of products stemming from direct allylic substitution from free morpholine.…”

Enantioselective Ir-Catalyzed Allylic Alkylation of Racemic Allylic Alcohols with Malonates

“…Notably, during our studies, Carreira reported an elegant methodology for the Ir-catalyzed allylation of branched allylic carbonates, in which the trimethyl orthoacetate acts as an enolate surrogate (Scheme 1). 8 Meanwhile, You et al disclosed an asymmetric Rh-catalyzed allylic alkylation of branched alcohols with 1,3-diketones. 9 Here we wish to report our own results.…”