Palladium‐Catalyzed Asymmetric Decarboxylative Cycloaddition of Vinylethylene Carbonates with Michael Acceptors: Construction of Vicinal Quaternary Stereocenters

Abstract

An efficient method for the diastereo- and enantioselective construction of vicinal all-carbon quaternary stereocenters through palladium-catalyzed decarboxylative cycloaddition of vinylethylene carbonates with activated Michael acceptors was developed. By using a palladium complex generated in situ from [Pd2(dab)3]⋅CHCl3 and a phosphoramidite ligand as a catalyst under mild reaction conditions, the process provides multifunctionalized tetrahydrofurans bearing vicinal all-carbon quaternary stereocenters in high yields with a high level of absolute and relative stereocontrol.

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

“…[20] They are increasingly regarded as key chemicali ntermediates for the preparation of acyclic carbonates and polycarbonates [21] and as ar oute towards cis-diols, [22] methanol, [23] allylic alcohols, [24] ionic liquids, [25] and oxygen-containing heterocyclic compounds. [26] The preparation of cyclic carbonates has long been the domain of organometallic complexes of metals such as Cr,C o, Al, and Sn, [27] which are generally used in combination with co-catalytic amounts of organic nucleophiles. The role of the metal centeri nt his reactioni s the activation of the epoxide for nucleophilic attack of the cocatalystt hrough coordination of the oxygen atom (Scheme 3).…”

Recent Advances in the Catalytic Preparation of Cyclic Organic Carbonates

“…[20][21][22] These COCs have been frequently associated with numerous applications involving them as non-protic solvents, precursors for poly(carbonate) synthesis, electrolyte solvents and more recently as useful intermediates in organic synthesis. [23][24][25] It is for these reasons, among others, that the interest in COC synthesis has slowly but surely shifted attention towards the preparation of more sophisticated synthetic intermediates, providing new catalytic processes that show increased reactivity behavior, improved enantio-and chemo-selectivity and amplified substrate scope with excellent functional group tolerance. These endeavors can ultimate lead to the creation of secondary products derived from COC intermediates with applications in (bio)polymer synthesis 26 and pharmaceuticals.…”

Multiple Absolute Stereocontrol in Pd-Catalyzed [3+2] Cycloaddition of Oxazolidinones and Trisubstituted Alkenes Using Chiral Ammonium–Phosphine Hybrid Ligands

“…While the combined use of common chiral phosphine ligands, such as MOP 38 (13) or BINAP 39 (14) with TBAB was ineffective in promoting the cycloaddition (Entry 4) or inducing stereoselectivity (Entry 5), BINOLderived phosphoramidite 40,41 15 could impart sufficient cata- lytic activity to the corresponding Pd complex (Entry 6). 12 However, the observed poor stereoselectivity could not be improved by a further screening of structurally different chiral phosphoramidites. These results emphasize the critical importance of the molecular architecture of 2¢X that features the triarylphosphine incorporating chiral ammonium ion component paired with an appropriate halide ion for achieving an otherwise difficult multiple stereocontrol in the Pd-catalyzed [3+2] cycloaddition.…”

“…From this standpoint, we assessed the viability of the asymmetric construction of three contiguous stereocenters including vicinal all-carbon quaternary stereocenters 8,12,3135 through the [3+2] annulation of racemic 5-vinyloxazolidinone 8a and 2-cyano-3-phenylacrylate 6a (Table 2). Thus, the reaction of 8a with 6a catalyzed by [Pd 2 (dba) 3 ]¢CHCl 3 and 2d¢I in toluene at 0°C furnished the desired densely substituted pyrrolidine 11a in an almost stereochemically pure form (Entry 1).…”