Lignin is a complex polymer deposited in the cell wall of specialised plant cells, where it provides essential cellular functions. Plants coordinate timing, location, abundance and composition of lignin deposition in response to endogenous and exogenous cues. In roots, a fine band of lignin, the Casparian strip encircles endodermal cells. This forms an extracellular barrier to solutes and water and plays a critical role in maintaining nutrient homeostasis. A signalling pathway senses the integrity of this diffusion barrier and can induce over-lignification to compensate for barrier defects. Here, we report that activation of this endodermal sensing mechanism triggers a transcriptional reprogramming strongly inducing the phenylpropanoid pathway and immune signaling. This leads to deposition of compensatory lignin that is chemically distinct from Casparian strip lignin. We also report that a complete loss of endodermal lignification drastically impacts mineral nutrients homeostasis and plant growth.

We report the development of a small footprint continuous electrochemical Taylor vortex reactor capable of processing kilogram quantities of material per day. This report builds upon our previous development of a scalable photochemical Taylor vortex reactor (Org. Process Res. Dev. 2017, 21, 1042; 2020, 24, 201–206). It describes a static and rotating electrode system that allows for enhanced mixing within the annular gap between the electrodes. We demonstrate that the size of the annular gap and the rotation speed of the electrode are important for both conversion of the substrate and selectivity of the product exemplified using the methoxylation of N-formylpyrrolidine. The employment of a cooling jacket was necessary for scaling the reaction in order to manage the heat generated by electrodes at higher currents (up to 30 A, >270 mA cm–2) allowing multimole productivity per day of methoxylation product to be achieved. The electrochemical oxidation of thioanisole was also studied, and it was demonstrated that the reactor has the performance to produce up to 400 g day–1 of either of the corresponding sulfoxide or sulfone while maintaining a very high reaction selectivity (>97%) to the desired product. This development completes a suite of vortex reactor designs that can be used for photo-, thermal-, or electrochemistry, all of which decouple residence time from mixing. This opens up the possibility of performing continuous multistep reactions at scale with flexibility in optimizing processes.

We report the development of a single-pass electrochemical Birch reduction carried out in a small footprint electrochemical Taylor vortex reactor with projected productivities of >80 g day –1 (based on 32.2 mmol h –1 ), using a modified version of our previously reported reactor [ Org. Process Res. Dev. 2021 , 25 , 7, 1619–1627], consisting of a static outer electrode and a rapidly rotating cylindrical inner electrode. In this study, we used an aluminum tube as the sacrificial outer electrode and stainless steel as the rotating inner electrode. We have established the viability of using a sacrificial aluminum anode for the electrochemical reduction of naphthalene, and by varying the current, we can switch between high selectivity (>90%) for either the single ring reduction or double ring reduction with >80 g day –1 projected productivity for either product. The concentration of LiBr in solution changes the fluid dynamics of the reaction mixture investigated by computational fluid dynamics, and this affects equilibration time, monitored using Fourier transform infrared spectroscopy. We show that the concentrations of electrolyte (LiBr) and proton source (dimethylurea) can be reduced while maintaining high reaction efficiency. We also report the reduction of 1-aminonaphthalene, which has been used as a precursor to the API Ropinirole. We find that our methodology produces the corresponding dihydronaphthalene with excellent selectivity and 88% isolated yield in an uninterrupted run of >8 h with a projected productivity of >100 g day –1 .

Combining continuous photochemistry and flow reactions in high-temperature/high-pressure water has enabled us to integrate a multistep sequence into a single process with a reduction in reaction time to <10 min compared to >24 h in batch. At the same time, applying this approach to different substrates has allowed us to increase previously low yields to levels high enough to make these reactions potentially useful for multistage synthesis. In this paper, we describe the [2 + 2] cycloaddition/fragmentation of 3,4,5,6-tetrahydrophthalic anhydride and propargyl alcohol and analogous compounds leading to bicyclic lactones to demonstrate how photochemistry and thermal chemistry can be combined using continuous flow techniques to create complex structures on a relatively large scale. We show how photochemical and high-temperature water flow reactors can be used to carry out a three-step reaction sequence as a single integrated and continuous process. The reaction time has been reduced by exploiting the enhanced acidity of high-temperature water/acetonitrile mixtures. The overall process is demonstrated on an equivalent productivity of a >1 kg/day productivity using lab-scale equipment. Our approach should be simple to scale up in an appropriate facility, for larger scale production of chemicals. Process analytical technology and modeling were used to support the reaction development, while UV and IR time-resolved spectroscopies have been used to provide a deeper understanding of the reaction mechanism.

The design for a new high-pressure-low-temperature infrared (IR) cell for performing experiments using conventional Fourier transform infrared or fast laser-based time-resolved infrared spectroscopy, in a range of solvents, is described. The design builds upon a commercially available compressor and cold end (Polycold PCC(®) and CryoTiger(®)), which enables almost vibration-free operation, ideal for use with sensitive instrumentation. The design of our cell and cryostat allows for the study of systems at temperatures from 77 to 310 K and at pressures up to 250 bar. The CaF2 windows pass light from the mid-IR to the ultraviolet (UV), enabling a number of experiments to be performed, such as Raman, UV-visible absorption spectroscopy, and time-resolved techniques where sample excitation/probing using continuous wave or pulsed lasers is required. We demonstrate the capabilities of this cell by detailing two different applications: (i) the reactivity of a range of Group V-VII organometallic alkane complexes using time-resolved spectroscopy on the millisecond timescale and (ii) the gas-to-liquid phase transition of CO2 at low temperature, which is applicable to measurements associated with transportation issues related to carbon capture and storage.

Lignin is a complex polymer precisely deposited in the cell wall of specialised plant cells, where it provides essential cellular functions. Plants coordinate timing, location, abundance and composition of lignin deposition in response to endogenous and exogenous cues. In roots, a fine band of lignin, the Casparian strip encircles endodermal cells. This forms an extracellular barrier to solutes and water and plays a critical role in maintaining nutrient homeostasis. A signalling pathway senses the integrity of this diffusion barrier and can induce over-lignification to compensate for barrier defects. Here, we report that activation of this endodermal sensing mechanism triggers a transcriptional reprogramming strongly inducing the phenylpropanoid pathway and immune signaling. This leads to deposition of compensatory lignin that is chemically distinct from Casparian strip lignin. We also report that a complete loss of endodermal lignification drastically impacts mineral nutrients homeostasis and plant growth.