81-81-2Relevant articles and documents
Ionic liquids: Efficient media for the lipase-catalyzed Michael addition
Fan, Yunchang,Cai, Dongxu,Wang, Xin,Yang, Lei
, (2018)
Recently, ionic liquids (ILs) have been regarded as ideal media for non-aqueous bio-catalysis. In this work, the synthesis of warfarin by the lipase-catalyzed Michael addition in IL media and the parameters that affected the warfarin yield were investigated. Experimental results demonstrated that the chemical structures of the ILs were a major factor for influencing the warfarin yield. The ILs containing the NTf2– anion were suitable reaction media due to the high chemical stability of this anion. The incorporation of the hydroxyl group on the IL cation significantly improved the lipase activity due to the H2O-mimicking property of this group. The lipase activity decreased by increasing the alkyl chain length on the IL cation due to the non-polar domain formation of the IL cation at the active site entrance of lipase. The ILs and lipase could be reused no less than five times without reduction in the warfarin yield.
Hypervalent Iodine(III)-Mediated Tosyloxylation of 4-Hydroxycoumarins
Xu, Bowen,Gao, Yiping,Han, Jianwei,Xing, Zejing,Zhao, Sihan,Zhang, Ziyang,Ren, Runlin,Wang, Limin
, p. 10136 - 10144 (2019)
An efficient approach was developed for synthesis of 3-tosyloxy-4-hydroxycoumarins under mild conditions by using Koser's reagents. The reaction tolerated various functional groups, and the products served as useful aromatic building blocks. Additionally, a plausible mechanism via iodonium ylide was proposed, and the oral anticoagulant Warfarin was synthesized in good yield.
Primary Amine Catalyzed Activation of Carbonyl Compounds: A Study on Reaction Pathways and Reactive Intermediates by Mass Spectrometry
Bencivenni, Giorgio,Calcaterra, Andrea,Ciogli, Alessia,Iazzetti, Antonia,Mazzoccanti, Giulia,Righi, Paolo,Villani, Claudio
supporting information, (2021/12/01)
The field of organocatalysis is expanding at a fast pace. Its growth is sustained by major stimuli, such as the effort toward an understanding of the mechanisms of reaction and catalytic processes in general, the elucidation of basic properties leading to stereocontrol and the search for broad applicability and scalability of the synthetic methodology. This paper reports a thorough study based on ESI-MS spectrometry of amino-organocatalyzed model reactions under different experimental conditions. Off-line reaction monitoring of mixtures containing different catalytic systems, by ESI-MSn showed the presence of several putative intermediate species, either in their protonated or sodiated forms. In addition, enantioselective chromatography of crude reactions provides the stereochemical outcome of asymmetric reactions. The bulk of the data collected offers a clue of the intricate pathways occurring in solution for the studied reactions.
Enantioselective Michael Addition Reaction Catalysed by Enantiopure Binuclear Nickel(II) Close-Ended Helicates
Arunachalam, Rajendran,Chinnaraja, Eswaran,Natarajan, Ramalingam,Samanta, Krishanu,Subramanian, Palani S.
, (2020/02/04)
The enantiopure Ni(II) helicates [Ni2L1RR.Cl2] (1), [Ni2L1SS.Cl2] (1′), [Ni2L2RR.Cl2] (2), [Ni2L2SS.Cl2] (2′) were synthesized by one-pot self-assembly technique from R-(+)- or S-(?)-1,1′-binaphthyl-2,2′-diamine, with 4-methyl-2,6-diformyl phenol or 4-tert-butyl-2,6-diformyl phenol and nickel salts. This binuclear double stranded Ni(II) helicates were characterized by ESI-MS, IR and single crystal X-ray structure wherever applicable. The extensive chiroptical studies suggest that the complexes are enantiopure in nature. The chirality transfer from ligand L1RR & L2RR to Ni(II) metal centre produced ΔΔ geometrical chirality, while their enantiomeric counterpart L1SS & L2SS produced ΛΛ chirality in their respective complexes.These enantiopure helicates were applied as catalysts in asymmetric Michael addition of 1,3-dicarbonyl compounds with β-nitrostyrene to produce nitroalkanes in good yield (96–98%) and ee (78–94%). (Figure presented.).
A Silica-Supported Catalyst Containing 9-Amino-9-deoxy-9-epi-quinine and a Benzoic Acid Derivative for Stereoselective Batch and Flow Heterogeneous Reactions
Ciogli, Alessia,Capitani, Donatella,Di Iorio, Nicola,Crotti, Simone,Bencivenni, Giorgio,Donzello, Maria Pia,Villani, Claudio
, p. 2020 - 2028 (2019/03/07)
A heterogeneous, silica-based catalyst containing 9-amino-9-deoxy-epi-quinine (or quinidine) and a derivative of benzoic acid was synthesized through radical thiol-ene click reaction. The acid component allows the in situ activation of cinchona amino group, acting as a bifunctional catalyst. The heterogenized catalysts efficiently promoted the reaction of ketones with trans-β-nitrostyrene, with diastereo- and enantioselectivity comparable to those of the homogeneous counterparts (dr up to 90:10 and 90 % ee). In addition, the catalyst retained a constant activity for at least four cycles. Finally, the supported catalyst (9-amino-9-deoxy-epi-quinine/achiral acid) was employed under continuous-flow conditions. Two enantioselective Michael reactions were in sequence performed with the same homemade packed-bed reactor. The addition of cyclohexanone to trans-β-nitrostyrene provided the evaluation of optimal residence time with high level of stereoselection (2 μL/min flow rate, 83 % ee). Furthermore, the flow reactor well performed in the preparation of warfarin (isolated yield 95 %, 78 % ee. in 16 h at room temperature). The dual (chiral amine/achiral acid) solid supported system, making an even easier work-out, represents a valuable tool for green chemistry and is attractive for large scale applications.