Novel Stereo-Induction Pattern in Pudovik Addition/Phospha-Brook Rearrangement Towards Chiral Trisubstituted Allenes

Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al., there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide-mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha-Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central-to-axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo-induction pattern in the Pudovik addition/phospha-Brook rearrangement cascade reaction.

Diastereo- and Enantioselective Synthesis of Tetracyclic Cycloheptanols through (4+3) Annulation via C-C/C-H Activation Cascade

Transition metal-catalyzed annulations of four-membered rings via C-C activation are powerful tools to construct complex fused and bridged ring systems. Despite significant progress in (4+1), (4+2) and (4+4) annulations, the (4+3) annulation remains unexplored. Herein, we develop an asymmetric Rh-catalyzed intramolecular (4+3) annulation of α-arylalkene-tethered benzocyclobutenols for the synthesis of dihydrofuran-annulated dibenzocycloheptanols with two discontinuous chiral carbon centers via a C-C and C-H activation cascade. The reaction features excellent diastereo- and enantioselectivities and 100 % atom economy, and is applicable to late-stage modification of complex molecules.

Catalytic Enantioselective Biltz Synthesis

The Biltz synthesis establishes straightforward access to 5,5-disubstituted (thio)hydantoins by combining a 1,2-diketone and a (thio)urea. Its appealing features include inherent atom and step economy together with the potential to generate structurally diverse products. However, control of the stereochemistry of this reaction has proven to be a daunting challenge. Herein, we describe the first example of enantioselective catalytic Biltz synthesis which affords more than 40 thiohydantoins with high stereo- and regio-control, irrespective of the symmetry of thiourea structure. A one pot synthesis of corresponding hydantoins is also documented. Remarkably, experimental studies and DFT calculations establish the reaction pathway and origin of stereoselectivity.

A Liquid-Liquid-Solid System to Manipulate the Cascade Reaction for Highly Selective Electrosynthesis of Aldehyde

Electrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid-solid system. Herein, we report a novel liquid-liquid-solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200-fold from 0.4 % to 80.4 % compared with the liquid-solid system at a high current density of 136 mA cm^-2 , which is the highest one up to date. In the tri-phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as-produced benzaldehyde can be in situ extracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions.

Tryptophan-Modulated Nanoscale Metal-Organic Framework for Coordinated Loading of Biomolecules for Cascade Production of Reactive Oxygen and Nitrogen Species

Owing to the high surface area and porosity, metal-organic frameworks (MOFs) could be utilized as both nanocarriers of biopharmaceuticals and nanoreactors to organize cascade biological reactions with great potential in cancer treatment. However, nanoscale MOFs suitable for biomedical applications rely on harsh preparation conditions. Here, we utilized tryptophan to modulate the morphology and optical properties of zeolitic imidazolate framework-8 (ZIF-8) as nanocarrier to efficiently encapsulate the enzyme and mRNA. Under room temperature in an aqueous solution, tryptophan would coordinate with zinc ions to form ZIF-8:Trp with a decreased size from the μm range to sub-200 nm. In addition, cargo release could be monitored in real time via fluorescence red-shift effects. Besides being used as nanocarriers of biomolecules, ZIF-8:Trp could also be utilized as nanoreactors to induce cascade reactions to produce reactive oxygen and nitrogen species. Overall, this nanosized ZIF-8:Trp could provide a new strategy for preparation of cascade bioreactions and provide new insight for gas therapy.

Concise total synthesis of (±)-actinophyllic acid

A concise total synthesis of the complex indole alkaloid (±)-actinophyllic acid was accomplished by a sequence of reactions requiring only 10 steps from readily-available, known starting materials. The approach featured a Lewis acid-catalyzed cascade of reactions involving stabilized carbocations that delivered the tetracyclic core of the natural product in a single chemical operation. Optimal conversion of this key intermediate into (±)-actinophyllic acid required judicious selection of a protecting group strategy.