Propargylic Carbonates Research Articles

Suzuki coupling for preparation of allenes – ligand effects and chirality transfer

o-(Diphenylphosphino)benzaldehyde has been identified as the effective ligand for the coupling of propargylic carbonates and organoboronic acids under mild conditions.

Robust Silver(I) Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with Carbon Dioxide under Ambient Conditions

AbstractInspired by the bulkier bis(triphenylphosphine)–silver cation‐induced mechanism of propargylic alcohols and carbon dioxide through the alkyl carbonate intermediate, a robust dual‐component catalytic system consisting of silver acetate and tetraheptylammonium bromide was rationally developed for the synthesis of α‐methylene cyclic carbonates under ambient conditions without employing any additional organic base and ligand. This is one of the most effective catalysts reported to date for this conversion, with a very high turnover number of up to 6024, probably due to the synergistic effect of Lewis basic and Lewis acidic species for the activation of both propargylic alcohol and carbon dioxide by the formation of the alkyl carbonate with a bulkier counterion. Notably, this catalyst also worked well for the carboxylative cyclization of propargylic amines with carbon dioxide with the highest turnover number of 544.magnified image

Synthesis of Allenes by Catalytic Coupling of Propargyl Carbonates with Aryl Iodides in the Presence of Diboron Species

Bimetallic copper-/palladium-catalyzed multicomponent reaction of propargyl carbonates, aryl iodides, and diboron species was studied. This procedure can be used for synthesis of di-, tri-, and tetra-substituted allenes. Using diboronic acid, the reaction is supposed to proceed via allenylboronic acid intermediate.

Silver(I)-Catalyzed Synthesis of β-Oxopropylcarbamates from Propargylic Alcohols and CO2 Surrogate: A Gas-Free Process.

The utilization of carbon dioxide poses major challenges owing to its high thermodynamic stability and kinetic inertness. To circumvent these problems, a simple reaction system is reported comprising ammonium carbamates as carbon dioxide surrogates, propargylic alcohols, and a silver(I) catalyst, for the effective conversion of a wide range of alcohols and secondary amines into the corresponding β-oxopropylcarbamates. A key feature of this strategy includes quantitative use of a carbon resource with high product yields under gas-free and mild reaction conditions. Notably, this catalytic protocol also works well for the carboxylative cyclization of propargylic amines and carbon dioxide surrogates to afford 2-oxazolidinones.

Pathways to Functionalized Heterocycles: Propargyl Rearrangement using B(C6F5)3

The reactions of propargyl amides, ureas, carbamates, and carbonates with B(C6F5)3 proceed via an intramolecular 5-exo-dig cyclization across the alkyne unit to yield the corresponding vinyl borate species. The generated sp2 carbocation is stabilized by the flanking heteroatoms, allowing for isolation of oxazoline intermediates. The fate of these intermediates is strongly dependent upon the propargyl-functionalized starting material, with the carbamates and carbonates undergoing a ring-opening mechanism (propargyl rearrangement) to give cyclic allylboron compounds, while prolonged heating of the urea derivatives shows evidence of oxazole formation. In a deviation away from the reactivity of carbamates stated previously, the benzyl carbamate substrate undergoes dealkylation at the benzylic position, liberating 5-methyloxazol-2-(3H)-one.

Silver-catalyzed Three-component Reaction of Propargylic Amines, Carbon Dioxide, and N-Iodosuccinimide for Stereoselective Preparation of (E)-Iodovinyloxazolidinones

The silver-catalyzed three-component reaction of propargylic amines, carbon dioxide, and N-iodosuccinimide for the stereoselective synthesis of (E)-iodovinyloxazolidinones was developed. The silver-catalytic system could be applied to various propargylic amines to afford the corresponding iodovinyloxazolidinones in high yields. The structure of the oxazolidinone was confirmed by X-ray structure analysis to be the E-isomer for the geometry of the exo-olefin. The silver-catalyzed cyclization and replacement of silver with the iodine group in the intermediate were thought to be crucial steps.

ChemInform Abstract: Access to Spirocyclized Oxindoles and Indolenines via Palladium‐Catalyzed Cascade Reactions of Propargyl Carbonates with 2‐Oxotryptamines and Tryptamines.

AbstractA variety of the desired N‐heterocyclic scaffolds, required for alkaloid preparation, is best available by reaction of the educts with propargyl carbonate (II).

Bubble-point measurement for the binary mixture of propargyl acrylate and propargyl methacrylate in supercritical carbon dioxide

Acrylate and methacrylate (acrylic acid type) are compounds with weak polarity which show a non-ideal behaviour. Phase behaviour of these systems play a significant role as organic solvents in industrial processes. High pressure phase behaviour data were reported for binary mixture of propargyl acrylate and propargyl methacrylate in supercritical carbon dioxide. The bubble-point curves for the (carbon dioxide+propargyl acrylate) and (carbon dioxide+propargyl methacrylate) mixtures were measured by static view cell apparatus at temperature range from 313.2K to 393.2K and at pressures below 19.14MPa. The (carbon dioxide+propargyl acrylate) and (carbon dioxide+propargyl methacrylate) systems exhibit type-I phase behaviour. The (carbon dioxide+(meth)acrylate) systems had continuous critical mixture curves with maximums in pressure located between the critical temperatures of carbon dioxide and propargyl acrylate or carbon dioxide and propargyl methacrylate. The solubility behaviour of propargyl (meth)acrylate in the (carbon dioxide+propargyl acrylate) and (carbon dioxide+propargyl acrylate) systems increases as the temperature increases at a fixed pressure. The experimental results for the (carbon dioxide+propargyl acrylate) and (carbon dioxide+propargyl methacrylate) systems correlate with the Peng–Robinson equation of state using a van der Waals one-fluid mixing rule. The critical properties of propargyl acrylate and propargyl methacrylate were predicted with the Joback–Lyderson group contribution and Lee–Kesler method.

ChemInform Abstract: Palladium‐Catalyzed Nucleophilic Substitution of Propargylic Carbonates and Meldrum′s Acid Derivatives.

The palladium-catalyzed reaction of propargylic carbonates with Meldrum's acid derivatives proceeds smoothly in the presence of Pd(OAc)2 and P(2-furyl)3 in THF at 80 °C to give substitution products. The substitution products can be useful intermediates for the stereoselective synthesis of functionalized (Z)-γ-alkylidene-γ-butyrolactones.

A C-H bond activation-based catalytic approach to tetrasubstituted chiral allenes.

Enantioselective synthesis of fully substituted allenes has been a challenge due to the non-rigid nature of the axial chirality, which spreads over three carbon atoms. Here we show the commercially available simple Rh complex may catalyse the CMD (concerted metalation/deprotonation)-based reaction of the readily available arenes with sterically congested tertiary propargylic carbonates at ambient temperature affording fully substituted allenes. It is confirmed that the excellent designed regioselectivity for the C–C triple bond insertion is induced by the coordination of the carbonyl group in the directing carbonate group as well as the steric effect of the tertiary O-linked carbon atom. When an optically active carbonate was used, surprisingly high efficiency of chirality transfer was realized, affording fully substituted allenes in excellent enantiomeric excess (ee).

ChemInform Abstract: Gold(I)‐Catalyzed Decarboxylation of Propargyl Carbonates: Reactivity Reversal of the Gold Catalyst from π‐Lewis Acidity to σ‐Lewis Acidity.

AbstractIn the catalyzed decarboxylative etherification of propargyl carbonates the gold(I) catalyst shows a distinct σ‐acidity and propargyl ethers are furnished.

ChemInform Abstract: Palladium‐Catalyzed Highly Efficient Synthesis of Functionalized Indolizines via Cross‐Coupling/Cycloisomerization Cascade.

AbstractA wide range of 1,3‐disubstituted indolizines are obtained by Pd‐catalyzed reaction of 3‐(2‐pyridyl) propargyl carbonates with organoboronic acids.

ChemInform Abstract: Copper‐Catalyzed Enantioselective Propargylic Etherification of Propargylic Esters with Alcohols.

AbstractA copper‐catalyzed enantioselective propargylic etherification of propargylic carbonates with simple alcohols and phenols is developed to provide propargylic ethers in good to excellent enantioselectivities.

ChemInform Abstract: Gold(I)‐Catalyzed 1,2‐Acyloxy Migration/[3 + 2] Cycloaddition of 1,6‐Diynes with an Ynamide Propargyl Ester Moiety: Highly Efficient Synthesis of Functionalized Cyclopenta[b]indoles.

AbstractA gold‐catalyzed cycloisomerization of 1,6‐diynes containing an ynamide propargyl ester or carbonate moiety is developed that provides an attractive route to diverse‐substituted 3‐acyloxy‐1,4‐dihydrocyclopenta[b]indoles.

Access to Spirocyclized Oxindoles and Indolenines via Palladium-Catalyzed Cascade Reactions of Propargyl Carbonates with 2-Oxotryptamines and Tryptamines.

Reported here are methods for the direct construction of a range of spirocyclized oxindoles and indolenines in good to excellent yields. Specifically, we report the palladium-catalyzed reactions of oxindoles and indoles, both functioning as bis-nucleophiles, with propargyl carbonates to afford spirocyclic products having an exocyclic double bond on the newly formed ring. The reaction proceeds through a process wherein the first nucleophilic unit on the oxindole or indole reacts with an allenyl-palladium species, formed from oxidative addition of Pd(0) to propargyl carbonates, to generate a π-allyl palladium intermediate that then reacts further with the second nucleophilic component of the oxindole or indole. The cascade process forges two bonds en route to spirocyclized oxindole and indolenine products. The use of chiral phosphines renders the cyclization sequence enantioselective, providing spirocyclic products with modest to good enantioselectivities.

Palladium‐Catalyzed Nucleophilic Substitution of Propargylic Carbonates and Meldrum's Acid Derivatives

AbstractThe palladium‐catalyzed reaction of propargylic carbonates with Meldrum's acid derivatives proceeds smoothly in the presence of Pd(OAc)2 and P(2‐furyl)3 in THF at 80 °C to give substitution products. The substitution products can be useful intermediates for the stereoselective synthesis of functionalized (Z)‐γ‐alkylidene‐γ‐butyrolactones.

ChemInform Abstract: Pd(0)‐Catalyzed Alkenylation and Allylic Dearomatization Reactions Between Nucleophile‐Bearing Indoles and Propargyl Carbonate.

Spiroindolenine derivatives were synthesized by intermolecular Pd-catalyzed dearomatization of indoles. The reaction between nucleophile bearing indoles and propargyl carbonate proceeds in a cascade fashion providing spiroindolenines or spiroindolines in good to excellent yields.

Palladium-catalyzed highly efficient synthesis of functionalized indolizines via cross-coupling/cycloisomerization cascade.

An efficient Pd-catalyzed cross-coupling/cycloisomerization of 3-(2-pyridyl) propargyl carbonates with organoboronic acids has been developed, which provides a straightforward route for the synthesis of 1,3-disubstituted indolizines with a wide variety of substituents. The mechanistic study indicates that the reaction proceeds via formation of an allenyl pyridine intermediate through palladium-catalyzed coupling reaction followed by cyclization.

Gold(I)-catalyzed 1,2-acyloxy migration/[3+2] cycloaddition of 1,6-diynes with an ynamide propargyl ester moiety: highly efficient synthesis of functionalized cyclopenta[b]indoles.

A gold-catalyzed cycloisomerization of 1,6-diynes containing an ynamide propargyl ester or carbonate moiety has been developed that provides an attractive route to a diverse-substituted 3-acyloxy-1,4-dihydrocyclopenta[b]indoles. Mechanistic studies indicate that the reaction likely proceeds through a competitive 1,2-OAc migration followed by [3+2] cycloaddition of the vinyl gold-carbenoid intermediate with the pendant triple bond. The synthetic utility of the obtained cyclopenta[b]indole products was demonstrated by their efficient transformations by deprotection or double-bond isomerization reactions.

ChemInform Abstract: Novel Method of Tetramic Acid Synthesis: Silver‐Catalyzed Carbon Dioxide Incorporation into Propargylic Amine and Intramolecular Rearrangement.

AbstractA new strategy for the synthesis of tetramic acids from propargylic amines and carbon dioxide under mild reaction conditions is presented.