Nickel-Catalyzed Rearrangement of 1-Acyl-2-vinylcyclopropanes. A Mild Synthesis of Substituted Dihydrofurans

Abstract

[reaction: see text] Mild Ni(0)-catalyzed rearrangements of 1-acyl-2-vinylcyclopropanes have been developed. The room-temperature isomerizations afford dihydrofuran products in yields regularly greater than 90%. A highly substituted, stereochemically defined cyclopropane was employed in the rearrangement to evaluate the reaction mechanism. Product analysis indicates that the overall reaction proceeds with retention of configuration at the vinyl-bearing stereogenic center.

Ein neues goldenes Zeitalter in der Chemie Donor‐Akzeptor‐substituierter Cyclopropane

“…Durch den Einsatz eines Ni 0 -NHC-Katalysators (NHC = N-heterocyclisches Carben) lässt sich die bençtigte Aktivierungsenergie für die Umlagerung von Vinylcyclopropanen entscheidend senken, sodass oftmals schon bei Raumtemperatur die Bildung von Cyclopentenen 100 a beobachtet werden kann (Tabelle 11, Nr. [93] Die gewählten Reaktionsbedingungen brachten oftmals eine spontane Aromatisierung des Reaktionsprodukts mit sich. [91] Auch wenn dieses Beispiel kein richtiges D-A-Cyclopropan ist, wurde es als natives CH-System der Vollständigkeit halber hier mit aufgenommen.…”

Gold‐Catalyzed Oxidative Ring Expansions and Ring Cleavages of Alkynylcyclopropanes by Intermolecular Reactions Oxidized by Diphenylsulfoxide

“…[16] As shown in Scheme 5, we observed a new catalysis involving the oxidative ring-cleavage of cyclopropylalkynes 8 using Ph 2 SO and the gold catalyst that gave 2,4-dien-1-one 9 in 74 % yield. [16] As shown in Scheme 5, we observed a new catalysis involving the oxidative ring-cleavage of cyclopropylalkynes 8 using Ph 2 SO and the gold catalyst that gave 2,4-dien-1-one 9 in 74 % yield.…”

“…Despite their elegant work, these oxygen donors were commonly used to generate gold a-carbonylcarbenoids [12] by intramolecular activation of alkynes. [7b, 15] In Table 1, we selected Ph 2 SO as the oxygen donor because amine oxide, pyridine oxide, [16] and imine oxide were inactive for the oxidation of alkynylcyclopropane 1 a when using [PPh 3 Au]SbF 6 . [7b, 15] In Table 1, we selected Ph 2 SO as the oxygen donor because amine oxide, pyridine oxide, [16] and imine oxide were inactive for the oxidation of alkynylcyclopropane 1 a when using [PPh 3 Au]SbF 6 .…”

“…Table 2 includes various alkynylcyclopropane derivatives 1 b-1 q bearing either an aryl or an amino group to ensure that attack of Ph 2 SO occurs only at the C b carbon atom. This gold catalysis is particularly suitable for aminoalkynylcyclopropanes 1 n-1 q; the reactions were completed within 2-5 hours, and gave desired cyclobutenyl amides in 91-95 % yields ( Table 2, entries [13][14][15][16]. Entries 1-6 of Table 2 show the effects of para-substituted phenyl substituents; we obtained excellent yields (92-95 %) of resulting cyclobutenyl ketones 2 b-2 c bearing electron-donating groups such as methyl and methoxy.…”

Molecular Rearrangements: Part 2. Other Reactions

“…86 The room temperature isomerizations afford ee dihydrofuran products in high yield. 86 The room temperature isomerizations afford ee dihydrofuran products in high yield.…”