Superactive tin(II) triflate/carbon nanotube catalyst for the Baeyer-Villiger oxidation

Water-Tolerant Trifloaluminate Ionic Liquids: New and Unique Lewis Acidic Catalysts for the Synthesis of Chromane

“…The superactive catalysts based on carbon nanomaterials as supports have been already demonstrated in our earlier studies (Markiton et al, 2017 , 2018 ). Extremely high activity of Sn(OTf) 2 immobilized on MWCNTs in promoting the Baeyer-Villiger oxidation was related to spherical nanosize Sn(OTf) 2 particles ( ca .…”

“…Metal triflates are reported to be water tolerant Lewis acids; some of them can be even recovered from the aqueous phases after the reaction and recycled without loss of activity, e.g., La(OTf) 3 , Zn(OTf) 2 , Yb(OTf) 3 , and LiOTf (Kobayashi and Manabe, 2000 ; Kobayashi et al, 2002 ). Other metal triflates are known to slowly hydrolyse in water, releasing triflic acid, thus acting sometimes as a Brønsted acid–this includes Al(OTf) 3 , Sn(OTf) 2 , Sc(OTf) 3 , and In(OTf) 3 (Baes and Mesmer, 1976 ; Noji et al, 2003 ; Markiton et al, 2018 ). As a rule of a thumb, metals at higher oxidation states are more prone to hydrolysis, with the exception of rare earth metal triflates, which are water-stable and act as Lewis acids in both aqueous and non-aqueous media (Kobayashi et al, 2002 ).…”

“…Kobayashi and co-workers found that certain Lewis acidic metal triflates (M = Al, Ga, Ln) are stable in aqueous media (Kobayashi and Manabe, 2000 ; Kobayashi et al, 2002 ). Following this, such metal triflates were reported as water-tolerant Lewis acidic catalysts for a range of organic transformations: aldol condensations, Diels-Alder reactions, Friedel-Crafts acylations and alkylations, radical additions, aromatic nitrations and sulfonylations (Lub et al, 2005 ; Coulombel et al, 2009 ; Robertson and Wu, 2010 ; Williams and Lawton, 2010 ; Prakash et al, 2012 ; Lemière and Duñach, 2013 ; Markiton et al, 2018 ). The metal triflate catalysts were active at low concentrations, bearing the promise of cost-effective and efficient processes, but suffered from limitations in solubility.…”

Highly Efficient Synthesis of Alkyl Levulinates from α-Angelica Lactone, Catalyzed with Lewis Acidic Trifloaluminate Ionic Liquids Supported on Carbon Nanotubes

“…9,10 SILP catalysts retain the important physical and chemical features of ILs, such as non-volatility, nonflammability and good thermal stability, while adding advantage in terms of catalyst recovery, regeneration and reuse. 25,26 Encouraged by our earlier work, 20,27,28 we decided to non-covalently support trifloaluminate ionic liquids on commercially available, inexpensive multi-walled carbon nanotubes Table 4. As expected, both the pore volume (Vp) and the overall surface area (SBET) were lower for the SILP, when compared to neat MWCNTs, which most likely results from the ionic liquid occupying the interstitial MWCNT bundle channels -forming both pores and the available surface.…”

“…2-Methyl-1-propyl levulinate: ( 1 H NMR, 400 MHz, CDCl 3 , TMS): δ 0.93 (d, J = 6.7 Hz, 6H), 1.97−1.87 (m, 1H), 2.20 (s, 3H), 2.59 (t, J = 6.6 Hz, 2H), 2.76 (t, J = 6.6 Hz, 2H), 3.86 (d, J = 6.7 Hz, 2H). 13 (7), 130 (5), 117 (20), 99 (100), 81 (6), 71 (23), 57 (27), 43 (80). (5), 155 (4), 142 (4), 127 (5), 112 (24), 99 (100), 83 (10), 71 (24), 57 (23), 43 (61).…”