Combined Rhodium/Gold Catalysis: From Propargyloxiranes to 2,5‐Dihydrofurans in One Pot

Abstract

A new and efficient one-pot synthesis of 2,5-dihydrofurans from propargyloxiranes and arylboronic acids takes advantage of sequential rhodium-gold catalysis. The transformation proceeds with center-to-axis-to-center chirality transfer and tolerates a wide variety of electron-accepting or electron-withdrawing substituents at the arylboronic acid, as well as cyclic or acyclic propargyloxiranes.

Bifunctionalized Allenes. Part XIII. A Convenient and Efficient Method for Regioselective Synthesis of Phosphorylated α-Hydroxyallenes with Protected and Unprotected Hydroxy Group

“…There are variety of methods for the construction of hydroxyallenes that include prototropic rearrangement of propargylic alcohols [14,15,16], metal-catalyzed nucleophilic addition of propargylic derivatives to aldehydes [17,18,19,20,21,22,23,24], Cu(I)-catalyzed reaction of propargylic chlorides with Grignard reagents [25,26,27], metal-catalyzed reaction of propargylic oxiranes with organometallic compounds [28,29,30,31,32,33,34,35] and ketones [36,37], reduction of alcohols, ethers, oxiranes etc. with aluminium reagents [38,39,40], Pd(0)-catalyzed reaction of cyclic carbonates with acetylenic compounds [41,42], S N 2’ [43,44] and A N [45,46,47] reactions of metalled alkoxy-allenes with oxiranes and ketones [5], and other routes [48,49].…”

Aquakultur – quo vadis?!

“…So kann der goldkatalysierten Cycloisomerisierung von a‐Hydroxyallenen eine rhodiumkatalysierte Synthese der Allene durch S N 2'‐Substitution vorangeschaltet werden. Die Umsetzung von Propargyloxiranen mit Arylboronsäuren und einem Rhodiumkatalysator in Gegenwart von KOH ergibt die α‐Hydroxyallene, die ohne Isolierung durch Zugabe von AuBr3 zu den entsprechenden 2,5‐Dihydrofuranen cyclisiert werden (Abbildung 10) 12. Der Schlüssel zur erfolgreichen Eintopfsynthese dieser Heterocyclen ist die Optimierung der Menge an KOH, da diese Base essenziell für die rhodiumkatalysierte S N 2'‐Substitution ist, aber gleichzeitig den Goldkatalysator deaktiviert.…”

Combined coinage metal catalysis for the synthesis of bioactive molecules

“…The latter reaction can be combined with the gold-catalyzed cycloisomerization to 2,5-dihydrofurans in a onepot process which enables an efficient and sustainable access to these heterocycles. Thus, treatment of propargyl oxirane 24 with various arylboronic acids in the presence of KOH and catalytic amounts of [RhCl(nbd)] 2 , followed by addition of the AuBr 3 catalyst, afforded dihydrofurans 25 with good to excellent yield (Scheme 12) [33]. The process tolerates both electron-donating and -withdrawing substituents in the arylboronic acid.…”