Asymmetric phase-transfer catalysis

Understanding the response of vegetation to drought is significant for socio-economic development and biodiversity conservation. However, due to the complexity of drought, relying only on one approach, such as the surrounding physical environmental conditions or specific vegetation characteristics, does not yield precise results. To address this challenge, composite drought indices incorporating normalized difference vegetation index (NDVI) and other multiple variables, have been developed and shown promising effectiveness in drought detection. Compared to NDVI, solar-induced chlorophyll fluorescence (SIF) decreases due to the increased non-photochemical quenching and reduced photosynthesis during short-term drought stress. This indicates a direct association between SIF and vegetation photosynthesis, offering advantages over NDVI in capturing drought effects. Nevertheless, SIF has not yet been fully integrated into composite drought indices. Therefore, this study focuses on assessing the advantages of SIF for short-term drought monitoring by constructing a new composite drought index (CPDI) using the Principal Component Analysis (PCA) method. Subsequently, CPDI is employed to forecast future drought conditions. Overall, CPDI performs exceptionally well as a composite drought index in drought trend analysis and drought event identification, indeed advancing the monitoring capability for short-term drought. Furthermore, the incorporation of SIF in CPDI, obtained from various data sources provides more timely monitoring of drought events, while the CPDI with NDVI reflects the cumulative effect of drought conditions over a longer period. In the future, it is potential to utilize the benefits of SIF in constructing drought indices or combine it with NDVI for comprehensive drought characterization. 

The composite drought index incorporated solar-induced chlorophyll fluorescence enhances the monitoring capability of short-term drought

Herein, for the first time we have explored the umpolung reactivity of vinylogous carbon center of diazo arylidene succinimide (DAS) through rhodium catalysis to achieve [2,3]-Stevens rearrangement of α-thioether esters. The protocol has successfully demonstrated the distal C-H bond functionalization of the α-thioether esters. Alongside, the carbenoid reactivity of DAS has also been achieved with Doyle-Kirmse reaction of allyl/propargyl phenyl sulfides. The protocol proved to be practical to synthesize a wide variety of [2,3]-Stevens rearrangement products exclusively and the possible side products emanating from Pummerer rearrangement and [1,2]-Stevens rearrangement were not observed. This catalytic protocol works smoothly in environmentally benign solvent under open air to afford the corresponding desired products with excellent diastereo-, regio- and chemo-selectivities in good to excellent yields. The protocol also proved to be scalable on gram quantity.

Umpolung Reactivity of Diazo Arylidene Succinimides: Distal C-H Functionalization of α-Thiocarbonyls from the Reactive Carbenoid Center.

An efficient cascade intramolecular cyclization/intermolecular nucleophilic addition reaction of allenyl benzoxazinone with isatin or isatin-derived ketimine has been established by using Pd0-π-Lewis base catalysis. A series of 3-hydroxy-2-oxindoles and 3-amino-2-oxindoles with quaternary carbon atoms at the C3 position were synthesized in good yields under mild conditions through this protocol.

Facile Synthesis of Quinoline-Substituted 3-Hydroxy-2-oxindoles and 3-Amino-2-oxindoles via a Palladium-Catalyzed Cascade Intramolecular Cyclization/Intermolecular Nucleophilic Addition Reaction.

Abstract In this publication, we reported a regio-, diastereoselective, and kinetically controlled reaction for synthesizing thioxothiazolidin-indolin-2-ones, oxoindolin-carbamodithioate hybrids, and their base-catalyzed conversion into dispirocyclopentanebisoxindoles. Obtaining only the kinetic thioxothiazolidin-indolin-2-one products together with their straightforward conversion to dispirocyclopentanebisoxindoles, excellent regio- and diastereoselectivity, easy reaction workup, and one-pot synthetic operation are considerable advantages of this work. 

pdf/regio-and-diastereoselective-synthesis-of-thioxothiazolidin-48dy23zzcv.pdf

Regio- and diastereoselective synthesis of thioxothiazolidin-indolin-2-ones, oxoindolin-carbamodithioate hybrids, and their base-catalyzed conversion into dispirocyclopentanebisoxindoles

3-Amino oxindole Schiff base has been used as an efficient and crucial synthon for highly enantioselective benzylation and allylation with benzyl bromides and allyl bromides in the presence of a 1,3-bis[O(9)-allylcinchonidinium-N-methyl]-2-fluorobenzene dibromide phase transfer catalyst under mild reaction conditions. A broad series of chiral quaternary 3-amino oxindoles were smoothly obtained in good to excellent yields with excellent enantioselectivities (up to 98% ee) with broad substrate generality. A typical scale-up preparation and subsequent Ullman coupling reaction were also smoothly performed, and a special and important chiral spirooxindole benzofuzed pyrrol scaffold with potential pharmaceutical and organocatalytic activities was successfully obtained.

Enantioselective Benzylation and Allylation of a Crucial Synthon of 3-Amino Oxindole Schiff Base Promoted by a Cinchonidinium Phase Transfer Catalyst to Enable the Effective Preparation of Chiral Quaternary 3-Amino Oxindoles.

Can Sif and Npq Be Used in the Photosynthesis Rate Simulation of Plants Subjected to Drought?

Highly Diastereoselective Mannich Reaction between 3-Amino Oxindole Schiff Base and Oxindole Ketimines–Direct and Effective Preparation of Adjacent Tetrasubstituted 3,3′-Bisoxindole Protected Diamines

A copper catalyzed Doyle–Kirmse reaction for the concise and effective preparation of multifunctional 3-allyl-3-(thio) succinimides

A Copper Catalyzed Doyle−Kirmse Reaction between Vinyl Diazosuccinimide and Allyl-Phenyl Thioetherfor the Concise and Effective Preparation of Multifunctional 3-Allyl-3-(Thio) Succinimides

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