Merging Organocatalysis with an Indium(III)‐Mediated Process: A Stereoselective α‐Alkylation of Aldehydes with Allylic Alcohols

Allylic Alcohols: Sustainable Sources for Catalytic Enantioselective Alkylation Reactions

“…The combination of undoubted synthetic potential and still significant chemical limitations suggests that much more is still to come in this fascinating area, with particular emphasis on substrate scope, catalyst efficiency, and likely, organocatalysis. [8] …”

Indium(III)‐Promoted Organocatalytic Enantioselective α‐Alkylation of Aldehydes with Benzylic and Benzhydrylic Alcohols

“…[7] Recently, we introduced the concept of enantioselective S N 1-type alkylations to organocatalysis, [8,9] and also established the compatibility of indiumA C H T U N G T R E N N U N G (III) Lewis acids with organocatalytic processes mediated by the MacMillan catalyst. [10,11] The compatibility of indiumA C H T U N G T R E N N U N G (III) salts in these processes creates the possibility of using carbocations that cannot be generated in the presence of Brønsted acids. [12] The stability of the carbocation involved in the process is the primary driving force for these S N 1-type reactions, and their use can be easily rationalized by the work of Mayr et al [13] In the presence of InBr 3 , allylic alcohols can provide straightforward access to alkylated aldehydes without the use of palladium or iridium salts.…”

“…Alternatively, by using indiumA C H T U N G T R E N N U N G (III) salts (triflate or bromide), the corresponding carbenium ion can be generated from the alcohols and intercepted by the enamine formed in situ with the MacMillan catalyst. [10][11] The compatibility of indiumA C H T U N G T R E N N U N G (III) salts with water, the amine, and an excess of aldehyde is the motivation for investigating this chemistry.…”

Allylalkohole: nachhaltige Substrate für die katalytische enantioselektive Alkylierung

“…Die Kombination aus chiralen weichen pSäuren und Allylalkoholen gewährleistet eine hoch chemoselektive Aktivierung der Olefingruppe und minimiert Deaktivierungsphänomene aufgrund der geringen Oxophilie dieser Substrate. In diesem Zusammenhang entwickelten Yamamoto et al eine enantioselektive intramolekulare allylische Aminierung primärer Alkohole (8) in Gegenwart eines chiralen Binaphan(D)-Hg(OTf) 2 -Komplexes. [6] Trotz der Giftigkeit von Quecksilberderivaten spricht die geringe Katalysatorkonzentration (1 Mol-%) in Verbindung mit den milden Reaktionsbedingungen (À30 8C, < 1 h Reaktionszeit) für die Anwendung dieses Protokolls in der Synthese von enantiomerenreinen N-Sulfonyl-2-vinylindolen 9 (99 % ee; Schema 4).…”

“…Das besondere Augenmerk liegt hierbei auf dem Substratspektrum, der katalytischen Aktivität und, voraussichtlich, der Organokatalyse. [8] Eingegangen am 18. Oktober 2010 Online veröffentlicht am 14.…”