Facile Synthesis of H-Phosphinates from P(OR)3 or ClP(OR)2 via SiO2-Promoted Hydrolysis.

H-Phosphinates represent a valuable class of organophosphorus building blocks and catalytic ligands. The existing synthetic approaches are generally associated with the use of strong acids, the need for meticulous treatment of intermediates, and the limitation of only P-aryl introductions. Following a comprehensive investigation into the unexpected SiO2-promoted hydrolysis observed during the chromatography workup of the crude R'P(OR)2 intermediates, we have developed an extremely simple and general synthetic route to H-phosphinates from commercially available Grignard reagents and P(OR)3. An alternative approach involved the use of ClP(OR)2 in place of P(OR)3, which proved to be a valuable strategy for the preparation of sterically hindered ArMgBr substrates bearing bulky ortho-substituted motifs. A library of 36 structurally diverse P-(cyclo)alkyl and P-(hetero)aryl H-phosphinates was thus obtained in moderate to high yields using this practical protocol. Furthermore, the CuCl2-mediated P(O)-H bond derivations were also examined, resulting in the formation of the corresponding EtOPhP(O)-X (X = O, N, S) compounds in nearly quantitative yields.

Stereoselective synthesis of (E)-α,ß-unsaturated esters: triethylamine-catalyzed allylic rearrangement of enol phosphates.

α,ß-Unsaturated esters are key structural motifs widely distributed in various biologically active molecules, and their Z/E-stereoselective synthesis has always been considered highly attractive in organic synthesis. Herein, we present a >99% (E)-stereoselective one-pot synthetic approach towards ß-phosphoroxylated α,ß-unsaturated esters via a mild trimethylamine-catalyzed 1,3-hydrogen migration of the corresponding unconjugated intermediates derived from the solvent-free Perkow reaction between low-cost 4-chloroacetoacetates and phosphites. Versatile ß,ß-disubstituted (E)-α,ß-unsaturated esters were thus afforded with full (E)-stereoretentivity by cleavage of the phosphoenol linkage via Negishi cross-coupling. Moreover, a stereoretentive (E)-rich mixture of a α,ß-unsaturated ester derived from 2-chloroacetoacetate was obtained and both isomers were easily afforded in one operation.

Synthesis of enol phosphates directly from ketones via a modified one-pot Perkow reaction.

A modified Perkow reaction, named Perkow-Shi reaction, was developed based on the one-pot α-tosyloxylation of ketones following by addition of P(iii)-reagents and 4 Å molecular sieves. Diversity of enol phosphates, as well as enol phosphonates, enol phosphinates, and enol phosphoramidates were synthesized in high yields directly from the ubiquitously available ketones instead of the unfavourable α-chloroketones under a mild and environmental friendly condition.

Enantioselective Rhodium-Catalyzed Hydrogenation of (Z)-N-Sulfonyl-α-dehydroamido Boronic Esters.

Highly enantioselective rhodium-catalyzed hydrogenation of (Z)-N-sulfonyl-α-dehydroamido boronic esters is realized for the first time using a JosiPhos-type ligand. This method has enabled convenient synthesis of a series of enantio-enriched N-sulfonyl-α-amido boronic esters in good yields and excellent enantioselectivities (up to 99% ee).

Fabrication of a ß-cyclodextrin-based self-assembly containing a redox-responsive ferrocene.

The current research involves fabrication of a redox-responsive self-assembly system based on a ferrocene (Fc)-containing ß-cyclodextrin (ß-CD) derivative (ßCD-EG-Fc). ßCD-EG-Fc was synthesized, and its redox-sensitive self-assembly behavior was investigated using various techniques. On the basis of the intermolecular host-guest recognition between the ß-CD group and the Fc moiety, ßCD-EG-Fc primarily formed network-like structures and then vesicles following aging for a specified time. The formation of these structures was primarily driven by hydrogen bonding. Conversely, the oxidized molecules (ßCD-EG-Fc+) self-assembled into cationic vesicles with the absence of host-guest complexation. Upon controlling the oxidation and reduction of Fc/Fc+, reversible aggregate transformation was achieved. The current study resulted in a deeper understanding of ß-CD/Fc redox-responsive self-assemblies and contributed to the development of a single-component host-guest inclusion model.

Redox-responsive self-assembly of ß-cyclodextrin and ferrocene double-headed amphiphilic molecules.

We present a redox-responsive self-assembly based on a unimolecular platform. Three double-headed amphiphilic molecules composed of ß-cyclodextrin (ß-CD) and ferrocene (Fc) each with an alkyl chain as a linker (ßCD-Cm-Fc, m = 2, 6, and 10) were synthesized, and their self-assembly behaviors were investigated. The molecules self-assembled into polydisperse micelles that transformed into vesicles upon oxidization of the Fc moieties to Fc+. 2D 1H NMR results suggest that although the three molecules formed aggregates with similar morphologies, their molecular configurations were different because of the different lengths of the alkyl chains. When the linker was a C2 chain, no host-guest complexes were formed, whereas host-guest recognition was detected for linker lengths of C6 and C10. For the oxidized state samples, there were no host-guest interactions for linker lengths of C2 and C6, whereas the alkyl chain was locked in the cavity of ß-CD by host-guest inclusion for the molecule with a C10 linker. Moreover, reversible redox-responsive self-assemblies based on the three ß-CD derivatives with a terminal Fc were successfully achieved. Our results enrich the field of ß-CD/Fc reversible self-assembly systems, and provide a possible unimolecular host-guest complexation model in host-guest chemistry.