Gold(i)-catalyzed hydroindolylation of allenyl ethers

Abstract

The gold(i)-catalyzed reaction/rearrangement of allenyl ethers has been investigated in the presence of indoles. Either hydroindolylation or alkylation of an indole with the pendant group of allenyl ether has been observed. The reaction outcome seems to be decided mainly by the nature of the pendant group of the allenyl ether. Control experiments are indicative of an inner sphere mechanism for the hydroindolylation reaction.

Gold‐Catalyzed Functionalization Reactions of Indole

“…[41] In addition, Klimber developed a mild synthesis of indolylenamides 25 by nucleophilic addition of indoles to gold-activated N-allenamides 24, [42] whereas Ramana and co-workers used allenyl ethers 26 for preparing indole allylethers 27 [43] (Scheme 11). [41] In addition, Klimber developed a mild synthesis of indolylenamides 25 by nucleophilic addition of indoles to gold-activated N-allenamides 24, [42] whereas Ramana and co-workers used allenyl ethers 26 for preparing indole allylethers 27 [43] (Scheme 11).…”

An Apparent Umpolung Reactivity of Indole through [Au]‐Catalysed Cyclisation and Lewis‐Acid‐Mediated Allylation

“…[12] Results and Discussion For this proposition,t he requisite substrate 1a was prepared by N-benzoylationo fi ndole with 2-iodobenzoic acid, followed by Sonogashira coupling with 3-butyn-1-ol, and subjected to cyclisation in the presence of 5mol %A u(PPh 3 )Cl as catalyst and 10 mol %A gSbF 6 additive in dichloromethane at room temperature. [13] The starting compound 1a disappeared completely within 2h with the formation of two new products,a s evidenced by TLC [ Table 1, Eq. 1].…”

Gold(I)‐Catalysed Hydroarylation of 1,3‐Disubstituted Allenes with Efficient Axial‐to‐Point Chirality Transfer

“…Although the intermolecular addition of amines (hydroamination) and alcohols (hydroalkoxylation) have been reported to proceed with efficient chirality transfer, efficient intermolecular asymmetric hydroarylation of allenes has proven more elusive. Racemic gold‐catalysed hydroarylation of allenes was first reported independently by Li in 2008 (with aryl nucleophiles) and in 2009 by both Widenhoefer (with indole nucleophiles, Scheme a) and Gagné (with MeO‐substituted aryl nucleophiles) ,. Two years later, Che and co‐workers reported their attempts at hydroarylations with chirality transfer, which resulted in racemic products (Scheme b) .…”

“…Racemic gold-catalysed hydroarylation of allenes was first reported independently by Li in 2008( with aryl nucleophiles) [15] and in 2009 by both Widenhoefer (with indole nucleophiles, Scheme1a) [16] and GagnØ (with MeO-substituted aryl nucleophiles). [17,[18][19][20][21] Twoy ears later,C he and co-workers reported their attempts at hydroarylationsw ith chirality transfer, which resulted in racemic products (Scheme1b). [22] They attributed the lack of chirality transfer to the competitive gold(I)-catalysed allene racemisation reaction.…”