Pd-Catalyzed Asymmetric Allylic Cycloaddition of N-Containing Allylic Carbonates with Isocyanates

Abstract

An efficient method for the enantioselective synthesis of cyclic ureas has been developed through Pd-catalyzed asymmetric allylic cycloaddition of readily accessible nitrogen-containing allylic carbonates with isocyanates. By using a palladium complex in situ generated from Pd 2 (dba) 3 •CHCl 3 and phosphoramidite L1 or L3 as a ligand under mild reaction conditions, the process afforded imidazolidinones and tetrahydropyrimidinones with high yields and high levels of enantioselectivities.

Recent Advances in Enantioselective Pd-Catalyzed Allylic Substitution: From Design to Applications

“…Guo’s group developed a tandem [3 + 2] cycloaddition/allylation reaction of methylene-trimethylenemethane to yield hexahydropyrazole­[5,1- a ]­isoquinoline derivatives in good-to-excellent enantioselectivities ( ee values up to 99%) and moderate E/Z ratios (up to 5/1; Scheme a) . Shortly afterward, Zhang’s group applied the same catalytic system for the synthesis of chiral ureas (imidazolidinones) through Pd-catalyzed cycloaddition of tosylamino-substituted allylic carbonates and isocyanates (Scheme b) …”

“… 720 Shortly afterward, Zhang’s group applied the same catalytic system for the synthesis of chiral ureas (imidazolidinones) through Pd-catalyzed cycloaddition of tosylamino-substituted allylic carbonates and isocyanates ( Scheme 292 b). 721 …”

“…720 Shortly afterward, Zhang's group applied the same catalytic system for the synthesis of chiral ureas (imidazolidinones) through Pdcatalyzed cycloaddition of tosylamino-substituted allylic carbonates and isocyanates (Scheme 292b). 721 Ooi's group disclosed the use of chiral ammoniumphosphine hybrid ligands L161 and L162 in cycloadditions of 5-vinyloxazolidinones with a range of activated trisubstituted alkenes. In this manner, a variety of heavily substituted pyrrolidines was accessible with high diastero-and enantioselectivity using catalyst Pd/L161 (Scheme 293a).…”

Straightforward synthesis of biologically valuable nonsymmetrical malonamides under mild conditions

“…Isocyanates with the –NCO functional group that common mesomeric structure can be presented as: –N δ − C δ + O δ − , 6 display the general feature of heterocumulenes of undergoing addition reactions with a broad spectrum of reagents, including nitrogen-, oxygen-, sulfur-, phosphine-, boron-based nucleophiles, 7 to construct linear compounds, cyclic compounds, and polymers. 8 It is well documented that the central carbon atom of the isocyanate group could be regiospecifically attacked by CBN reagents to access amides with high selectivity, making isocyanates outstanding reagents for the construction of amides. 9 Mechanistically, these CBNs can be generally divided into two categories: 10 (1) nucleophilic, moisture sensitive organometallic species, including Grignard reagents, organozinc reagents, alkylaluminium compounds, etc .…”

Chiral Phosphoric Acid Catalyzed Asymmetric Desymmetrization of para-Quinamines with Isocyanates: Access to Functionalized Imidazolidin-2-one Derivatives

“…Isocyanates as versatile reactant and carbamate nitrogen-nucleophile participated in transition-metal catalyzed asymmetric reaction were well-documented. − However, organocatalytic asymmetric reaction with isocyanates was relatively rare. In 2016, the group of Liu developed a bifunctional bisguanidinium salt catalyzed asymmetric esterification/aza-Michael cascade between 2-hydroxyphenyl-substituted enones and isocyanates, and this catalyst was acted as a strong organic base .…”