Stereoselective tandem iridium-catalyzed alkene isomerization-cope rearrangement of ω-diene epoxides: efficient access to acyclic 1,6-dicarbonyl compounds

Abstract

The Cope rearrangement of 2,3-divinyloxiranes, a rare example of epoxide C-C bond cleavage, results in 4,5-dihydrooxepines which are amenable to hydrolysis, furnishing 1,6-dicarbonyl compounds containing two contiguous stereocenters at the 3- and 4- positions. We employ...

Recent Advances in Catalytic [3,3]-Sigmatropic Rearrangements

“…Marek's group used Ir-catalyzed Cope rearrangements to produce medium-sized ring structures through ring expansion reactions. In 2019, 7-memebered dienes were synthesized from alkenyl ω-ene cyclopropanes or epoxides 147 via Ir-catalyzed tandem olefin migration and Cope rearrangement (Scheme 30) [67,68]. Migration of the terminal olefin successfully occurred in the presence of a cationic Ir catalyst system to produce 1,5-dienes 148.…”

Chemical kinetics and promoted Co-immobilization for efficient catalytic carbonylation of ethylene oxide into methyl 3-hydroxypropionate

“…In the past decades, carbonyl metallic salts have been used as operatable homogeneous catalysts for carbonylation of epoxides. In fact, researchers have reported in detail on the ring expansion and ring-opening carbonylation of epoxides (Suresh et al, 2021). However, complicated homogeneous reaction systems were dominantly used with metastable metal carbonyls with unsatisfied product yields.…”

Stereodivergent Access to Trisubstituted Alkenylboronate Esters through Alkene Isomerization

“…To challenge the two hypotheses presented above, our model substrate 1a (R = n -Pr), easily synthesized through the Ni-catalyzed hydroalumination-transmetalation sequence of alkynes developed by Hoveyda, 37 was first submitted to our slightly modified Ir-based isomerization conditions (see Supporting Information ). 35 , 47 − 49 …”

“…During the course of our study, Huang and Guo et al have reported an elegant Fe–H-catalyzed isomerization resulting in trisubstituted ( Z )-alkenyl­boronates (Scheme f), leading us to disclose our results herein. For the formation of ( E )-alkenyl­boronates, our strategy relies on an Ir-based alkene isomerization catalyst operating through a 1,3-hydride shift mechanism. ,− In this mechanistic scenario, the key allyl iridium hydride intermediate prefers a “W-shaped” conformation where the substituents at the termini of the allylic system point away from the bulky iridium center ( A , Scheme a) rather than toward it ( B ). Reinsertion of the hydride would result in the formation of the E -alkenyl­boronate ester.…”

“…A preliminary substrate scope for the Ru-catalyzed isomerization is presented in Scheme b. Linear and branched alkyl chains [( Z )- 2a and ( Z )- 2c )] do not pose any challenges (see Supporting Information), ,− and as anticipated, the stereoselectivity of the reaction increases with the steric demand of the substituent. Protected alcohol-containing product ( Z )- 2d can be obtained with minimal formation of the silyl enol ether side product resulting from over­isomerization, provided the reaction is closely monitored.…”