Palladium‐Catalyzed Diastereo‐ and Enantioselective Synthesis of Substituted Cyclopentanes through a Dynamic Kinetic Asymmetric Formal [3+2]‐Cycloaddition of Vinyl Cyclopropanes and Alkylidene Azlactones

Abstract

An enantioselective preparation of vinylcyclopentanes has been achieved through the title reaction (see scheme). A range of aryl, heterocyclic, alkenyl, and alkyl substituted azlactone alkylidenes have been utilized, giving the cyclopentane products in good yield, diastereomeric ratio, and enantioselectivity.

Polarity Inversion of Donor–Acceptor Cyclopropanes: Disubstituted δ-Lactones via Enantioselective Iridium Catalysis

“…Although similar capabilities may be envisioned for corresponding D-A cyclopropane-mediated processes, π-allyl generation requires a malonic ester moiety to function as an efficient nucleofuge for oxidative addition, 7 which at the onset of these studies had not been demonstrated for iridium. Further, as reported by one of the present authors, 5d under the conditions of palladium catalysis, D-A cyclopropanes and aldehydes combine by way of π-allyl intermediates to form tetrahydrofurans (conceptualized in Figure 1c). Thus, the proposed umpoled process must compete with an efficient π-allyl mediated transformation involving identical reactants, rendering the outcome of this endeavor uncertain.…”

“…5 While the generation of nucleophilic π-allyls from D-A cyclopropanes is unknown (Figure 1d), 4 the feasibility of umpoled carbonyl additions involving D-A cyclopropanes is suggested by recently developed reductive couplings of allylic carboxylates to carbonyl partners catalyzed by ortho -cyclometallated iridium C,O -benzoates. 6,7 A unique feature of such iridium catalyzed carbonyl allylations resides in the use of alcohols as terminal reductants, allowing highly enantioselective carbonyl addition from the alcohol or aldehyde oxidation level in the absence of stoichiometric metallic reagents.…”

“…5d In preliminary experiments, vinylcyclopropane 1a (200 mol%) and benzyl alcohol 2a (100 mol%) were exposed to the chromatographically isolated π-allyliridium complex ( R )- I (5 mol%) at 50 °C under conditions effective for related crotylations employing α-methyl allyl acetate. 7d Gratifyingly, the desired adduct 4a formed as a single regioisomer with nearly complete levels of diastereo- and enantioselectivity, although the isolated yield was modest (Table 1, entry 1).…”

Potent Anticonvulsant 1H-Imidazol-5(4H)-One Derivatives with Low Neurotoxicity

“…The obtained crystalline product was washed with water then aqueous ethanol and crystallized from ethanol to give white crystalline solid of the oxazolone derivative. Compounds 2a-d were characterized and confirmed by comparison with literature data [18,19]. Compounds 3a, 3c, 3d, 3f, 3g, 3i, 3l, 3m, 3o, 3r, 3s and 3x [20][21][22][23][24][25][26][27][28] were prepared according to the general method and structures were confirmed via comparison with literature data.…”

Synthesis and Reactivity of Donor-Acceptor Substituted Aminocyclopropanes and Aminocyclobutanes

“…It has allowed the discovery of new reactivities between 1,3 dipoles and dipolarophiles such as cross cycloaddition [169][170][171]. This is 4 For examples of Pd catalyzed annulations, see [160][161][162][163]. 5 It is important to remark that [3 + 2] annulations involve mainly carbon-and alkoxy-substituted DA cyclopropanes.…”