Intramolecular Oxonium Ylide Formation–[2,3] Sigmatropic Rearrangement of Diazocarbonyl-Substituted Cyclic Unsaturated Acetals: A Formal Synthesis of Hyperolactone C

Abstract

Rh(II)-catalyzed oxonium ylide formation-[2,3] sigmatropic rearrangement of α-diazo-β-ketoesters possessing γ-cyclic unsaturated acetal substitution, followed by acid-catalyzed elimination-lactonization, provides a concise approach to 1,7-dioxaspiro[4.4]non-2-ene-4,6-diones. The process creates adjacent quaternary stereocenters with full control of the relative stereochemistry. An unsymmetrical monomethylated cyclic unsaturated acetal leads to hyperolactone C, where ylide formation-rearrangement proceeds with high selectivity between subtly nonequivalent acetal oxygen atoms.

Aqueous Exfoliation of Graphite into Graphene Assisted by Sulfonyl Graphene Quantum Dots for Photonic Crystal Applications

“…The existence of C−S bonding is further proved by the high-resolution C 1S XPS spectrum (Figure S2) and S 2P XPS spectrum (Figure 1d), which show the presence of sulfonyl functional groups (SO 3 ). 36,37 These results confirm the successful grafting of sulfonyl groups onto GQDs.…”

“…The existence of C–S bonding is further proved by the high-resolution C 1S XPS spectrum (Figure S2) and S 2P XPS spectrum (Figure d), which show the presence of sulfonyl functional groups (SO 3 –1 , 167.5 eV). In the FTIR spectrum of S-GQDs, several characteristic vibrational bands at 1175, 1405, 1610, 1730, 2930, and 3460 cm –1 are found, which are assigned to the stretching vibrations of C–S/C–O, bending vibrations of C–H, vibrational bands of CC, stretching vibrations of −CO, stretching vibrations of C–H, and the stretching vibrations of C–OH, respectively (see the Supporting Information, Figure S3). , These results confirm the successful grafting of sulfonyl groups onto GQDs.…”

The Synthesis of Amphiphilic Luminescent Graphene Quantum Dot and Its Application in Miniemulsion Polymerization

“…In Figure 3, the characteristic vibrational bands at 1090, 1370, 1710, 2920, and 3380 cm −1 were found, which can be assigned to the stretching vibrations of C-N/C-O, vibrational band of carboxylate ion (-COO − ), the overlapped vibrational absorption bands of C=C and HN-(C=O)-R, the C-H stretching vibration, and the stretching vibrations of C-OH and N-H. These results indicated that the hydrophobic groups (i.e., alkyl groups) were functionalized by amide bonds [36][37][38].…”

Highly Biocompatible, Underwater Superhydrophilic and Multifunctional Biopolymer Membrane for Efficient Oil–Water Separation and Aqueous Pollutant Removal

“…In the FTIR spectrum of KGMF, several characteristic vibrational bands were observed at 1249, 1406, 1660, 2925, and 3346 cm –1 , matching the stretching vibrations of CO, bending vibrations of CH, stretching signals of CO from amide groups, stretching peaks of CH of alkane groups, and the stretching vibrations of OH of hydroxyl groups, respectively (Figure S2). , We also performed FTIR characterization of pristine fabrics, whereas the amide peak at 1660 cm –1 was missing, indicating that the addition of TDI allowed the formation of a quasi-polyurethane structure. Both pristine fabrics and KGMF revealed a broad peak at ∼3350 cm –1 , confirming the presence of large amounts of OH groups which are crucial for developing underwater superoleophobic surface.…”