Gold(I)‐Assisted α‐Allylation of Enals and Enones with Alcohols

Abstract

The intermolecular α-allylation of enals and enones occurs by the condensation of variously substituted allenamides with allylic alcohols. Cooperative catalysis by [Au(ItBu)NTf2] and AgNTf2 enables the synthesis of a range of densely functionalized α-allylated enals, enones, and acyl silanes in good yield under mild reaction conditions. DFT calculations support the role of an α-gold(I) enal/enone as the active nucleophilic species.

A Gold(I)‐Catalyzed Domino Coupling of Alcohols with Allenes Enables the Synthesis of Highly Substituted Indenes

“…Inspired by a report by Bandini and co‐workers on the gold‐assisted α‐allylation of enals and enones using an allenamide as precursor (Scheme b), we envisioned a synthetic route in which an aryl‐substituted allene reacts with an alcohol to undergo a domino C−C coupling sequence –. Such a reaction would form two C−C bonds in inter‐ and intramolecular fashion, and therefore lead to highly substituted indenes in a single step with water as the only reaction byproduct.…”

“…Further experiments to investigate the mechanism of the reaction were carried out employing the allenes in the presence of activated alcohols. Firstly, as also observed by the Bandini group, we wanted to clarify the role of allylic ether I , which is a typical byproduct of the gold‐catalyzed allylation reaction. Premixing of allylic alcohol 2 a and gold catalyst A in CD 2 Cl 2 resulted in an equilibrium ratio of alcohol 2 a : ether I of 1:6.7.…”

Gold‐Catalyzed Allylation Reactions

“…The use of electrophilic AuCl 3 /AgSbF 6 or AuCl 3 resulted in the new C−C bond linkage in excellent yield with relatively mild reaction conditions (Scheme a,b, respectively) . Bandini and co‐workers documented the α‐allylic alkylation of α,β‐unsaturated carbonyls by condensation of allenamides ( 11 ) and 7 b ‐type π‐alcohols . The methodology (Au(I t Bu)Cl/AgNTf 2 , 2.5:7.5 mol %) was efficiently applied to the alkylation of enals, enones, and acylsilanes.…”

Nickel-Catalyzed Cross-Coupling of Allyl Alcohols with Aryl- or Alkenylzinc Reagents

“…However, direct catalytic transformation of allyl alcohols is more step- and atom-economical because the activated allylic substrates were mostly prepared from allyl alcohols. Hence, catalytic allylation using allyl alcohols as electrophiles attracted considerable attention in recent years. ,− For example, palladium-, rhodium-, and iridium-catalyzed cross-coupling of allyl alcohols with organoboron reagents have been achieved. , Transition-metal-catalyzed allylic alkylation of ketones, aldehydes, and other active methylene compounds using allyl alcohols were also carried out. , However, nucleophiles used in the transformation of allyl alcohols are very limited. Among those nucleophiles often employed in cross-coupling reactions such as organo-magnesium, -zinc, -boron, -tin, and -silicon reagents, only organoboron reagents were used to react with allyl alcohols.…”