ChemInform Abstract: Diastereodivergent Catalysis Using Modularly Designed Organocatalysts: Synthesis of Both cis‐ and trans‐Fused Pyrano[2,3‐b]pyrans.

Abstract

Cis‐ and trans‐fused 3,4,4a,8a‐tetrahydro‐2H,5H‐pyrano[2,3‐b]pyran‐7‐carboxylates are obtained in high diastereoselectivities and enantioselectivities from the same starting materials using a tandem inverse‐electron‐demand hetero‐Diels—Alder/oxa‐Michael reaction catalyzed by modularly designed organocatalysts.

Stereodivergent Catalysis

“…Recently, a diastereodivergent asymmetric electron-demand oxa-hetero-DA reaction has been developed by Zhao and coworkers. 631 An excellent inversion of the diastereoselectivity was observed in the reaction of β,γ-unsaturated α-keto esters 335 with α,β-unsaturated 1,7-dicarbonyl compounds 759 using L-Pro and different Cinchona alkaloid-derived thioureas 760 and 761 (Scheme 286). In the case of thiourea 760 pyranopyrans cis-762 were predominantly formed and with the organocatalysts 761 diastereomers trans-763 were obtained.…”

Palladium-catalysed diastereodivergent inverse-electron-demand oxa-Diels–Alder reactions of in situ formed cyclopentadienones via ligand-control

“…Furthermore, diastereodivergent catalysis, 8 a challenging but efficient strategy to access diverse chiral products with multiple stereogenic centers, has been seldom reported in asymmetric IED oxa-Diels-Alder reactions. 9 Recently, our group showed that Pd(0) could serve as a π-Lewis base catalyst to activate 1,3-dienes or 1,3-enynes by forming η 2 -coordinated complexes with a higher HOMO energy, enabling the enantioselective vinylogous Friedel-Crafts addition to N-sulfonylimines. 10 We further extended this strategy to activate labile and electron-poor cyclopentadienone by generating the relevant η 2 -Pd(0)-complex via the isomerisation of in situ formed 1,2-carbodipole species from the carbonate of 4-hydroxy-2-cyclopentenone (1a), which successfully underwent the IED aza-DA reaction, the vinylogous Morita-Baylis-Hillman reaction or the cross Rauhut-Currier-type reaction with various electrophilic reagents with high stereoselectivity (Scheme 1c).…”

Chiral phosphoric acid-catalyzed stereodivergent synthesis of trisubstituted allenes and computational mechanistic studies

“…However, modulation the sense of diastereoselectivity in an asymmetric catalytic reaction is still challenging, because the diastereochemical preference is largely governed by the inherent structure and stereoelectronic nature of the substrates 32 . To address this intrinsic problem, a series of ingenious strategies have been developed for asymmetric diastereodivergent catalysis [33][34][35] , such as using distinct catalysts [36][37][38] , change of metal cations 39 , and ligands 40,41 of the catalysts, change of reaction conditions 42,43 , stereodivergent dual catalysis [44][45][46][47][48][49][50] and stepwise control [51][52][53][54] . Nevertheless, achieving asymmetric diastereodivergent catalysis through modifications of one single type of chiral catalysts remains elusive 55,56 .…”