Iridium-Catalyzed Enantioselective Allyl–Allyl Cross-Coupling of Racemic Allylic Alcohols with Allylboronates

Abstract

Carreira’s iridium-(P, olefin) phosphoramidite-based catalytic system that allows asymmetric allyl–allylboronate cross-coupling with high enantioselectivity is reported. This transformation tolerates a large variety of racemic branched allylic alcohols and allylboronate substrates. The utility of the coupling is demonstrated in a concise catalytic asymmetric synthesis of (−)-preclamol.

Rh-Catalyzed Cycloisomerization of 1,7-Ene-Dienes to Synthesize trans-Divinylpiperidines: A Formal Intramolecular Addition Reaction of Allylic C–H Bond into Dienes

“…The reaction starts with the oxidative addition of an allylic C–H bond by a rhodium cation to give Rh–H intermediate II , which then undergoes insertion of the internal alkene of diene into the Rh–H bond to give a bis-allylic Rh complex, intermediate III . Afterward, intermediate III undergoes reductive elimination to give the final cyclization product . This reaction is similar to our previously reported cycloisomerization of ene-2-dienes .…”

A Concise Enantioselective Synthesis of (S)-Preclamol via Asymmetric Catalytic Negishi Cross-Coupling Reaction

“…The main synthetic strategies are based on the resolution of racemic compounds including methyl 5-oxo-4-phenylpentanoate, 10 3-(3-methoxyphenyl)-N-propylpiperidine, 11 and preclamol; 12 deriving from L-pipecolinic acid, 13 and asymmetric catalytic reactions involving Suzuki-Miyaura coupling of heterocycles, 14 hydrogenation of -substituted lactones, 15 allylic alkylation of branched carbonates, 16 allylboration of alkenes, 17 or allyl-allyl cross-coupling of allylic alcohols. 18 However, there are some limitations associated with these reported processes. For example, Wu and coworkers demonstrated that (S)-preclamol could be prepared from stoichiometric amounts of L-pipecolinic acid through 10 steps.…”

Nickel-Catalyzed Homo- and Cross-Coupling of Allyl Alcohols via Allyl Boronates

“…Transition-metal-catalyzed allyl–allyl cross-coupling reactions between allylic electrophiles and allylmetal reagents such as allyl Grignard reagents, allyl boronates, allyl-silanes, or allyl-stannanes represent some of the most efficient methods for the synthesis of 1,5-dienes (Scheme ), which are valuable building blocks in organic synthesis and also found in many biologically active substances and naturally occurring terpenes (Figure ). Such allyl–allyl couplings are significantly challenging because both homo- and cross-couplings might be involved in these reactions; therefore, it is hard to obtain the desired products with high chemo- and regioselectivity and good yields.…”

“…Such allyl–allyl couplings are significantly challenging because both homo- and cross-couplings might be involved in these reactions; therefore, it is hard to obtain the desired products with high chemo- and regioselectivity and good yields. To date, transition metals such as palladium, nickel, copper, iridium, and gold have been used to catalyze allyl–allyl cross-couplings. − Notwithstanding the advances, these reactions require pre-prepared stoichiometric allyl organometallic reagents, which are usually sensitive to air and moisture and suffer from low stability and low functional-group tolerance. In addition, most of these studies use activated derivatives such as allylic halides, esters, and phosphates as the electrophiles. − These substrates are often prepared from allylic alcohols.…”

“…To date, transition metals such as palladium, nickel, copper, iridium, and gold have been used to catalyze allyl–allyl cross-couplings. − Notwithstanding the advances, these reactions require pre-prepared stoichiometric allyl organometallic reagents, which are usually sensitive to air and moisture and suffer from low stability and low functional-group tolerance. In addition, most of these studies use activated derivatives such as allylic halides, esters, and phosphates as the electrophiles. − These substrates are often prepared from allylic alcohols. The direct employment of allylic alcohols as the allylic electrophiles is much more attractive because of its easy availability, high stability, and atom economy .…”