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Biostimulants are receiving increasing attention for their beneficial effects on crops, driving interest in identifying new plant extracts that could exert such stimulatory effects. This work aimed to evaluate the potential of an aqueous extract obtained from duckweed (Lemna minor L.), a freshwater species, to act as a biostimulant in maize. For this purpose, duckweed plants were collected from a natural basin and then transferred, stabilized, and grown under controlled conditions. The duckweed extract was first characterized through untargeted profiling, which revealed an abundance of bioactive phytochemicals. A relatively high amount of low-molecular-weight secondary metabolites such as phenolics (6714.99 mg kg−1) and glucosinolates (4563.74 mg kg−1) were present in the plant extract. Maize seeds were primed with different concentrations of this extract (0.01%, 0.05%, 0.50%, and 1.00%, dry weight/water volume), and some physiological and biochemical traits of the crop were recorded. The duckweed extract improved maize germination, biomass, leaf area, pigment content, and vigor index. The most effective treatment was the 0.50% concentration, which improved the majority of the measured growth traits. The extract at concentrations of 0.05%, 0.50%, and 1.00% stimulated the assimilation of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), and copper (Cu). In summary, this study revealed that duckweed is a promising species that can be cultured and grown under controlled conditions for obtaining extracts with biostimulant properties.

The use of Light Emitting Diode (LED) lights in microscale vegetable production is more and more widespread. In this context, the effect of light spectrum on photosynthesis, growth, shoot yield, pigment content, and nutritional status of einkorn seedlings (Triticum monococcum L. ssp. monococcum), germinated and grown in a nutrient solution, was investigated. Plants were subjected to six different LED light treatments, all having a photon flux density (PFD) of 200 &mu, mol m&minus, 2 s&minus, 1. Two light treatments were monochromatic (red or blue), three dichromatic (blue and red in the proportion), and one of a wider spectrum (selected as a control). All the light treatments affected the morphological, biochemical, and nutritional status of einkorn seedlings. Overall, the dichromatic treatments were the most effective in stimulating biomass production, CO2 assimilation, and evapotranspiration, as well as contents in chlorophyll a and b and carotenoids, and additionally nitrogen, phosphorous, manganese, iron, and zinc. These results are of relevance for the beneficial effects of dichromatic LED treatments in maximizing einkorn shoot yield and nutritional values, and in limiting energy consumption in indoor cultivation.

A new protocol for the diasteroselective synthesis of pyrrolidin-2-ones 4–14 is presented. Aquivion PFSA effectively catalyzed the diasteroselective nitro-mannich/lactamization cascade reaction between the imine formed from aldehydes 1a–g and amines 2a–b with methyl 3-nitropropanoate 3. The use of flow conditions allow a very efficient waste minimization confirmed by representative green metrics calculations.

A powerful, novel approach to meroterpenes conicol, epiconicol and didehydroconicol has been achieved via a key step Diels–Alder reaction of ( E )-3-methyl-1-(2′,5′-dimethoxyphenyl)buta-1,3-diene as diene with methyl vinyl ketone, methyl acrylate or methyl propiolate as dienophiles. Activation by high pressure (9 kbar) or by the use of Lewis acid catalysts, allows the Diels–Alder reaction to proceed in excellent yield and diastereoselectively to form cyclohexenyl-benzene cycloadducts, which are useful precursors for conicols. The successful total syntheses of conicol, epiconicol and didehydroconicol, are described.

A clean and efficient protocol for the synthesis of a wide variety of N-Boc-s-amino ketones 3a-g has been defined using flow approach. The multistep procedure is based on the s-azidation of unsaturated ketones, consecutive reduction of the azido group, and concomitant amino group protection, and furnishes the desired products in good yields and very low E-factors ranging from 3.1 to 5.6. In batch conditions and by water as reaction medium, poorer yields and complicated reaction mixtures are obtained. Adoption of the flow approach, which combines transformations performed in solvent-free conditions and in EtOAc, has been essential in order to avoid side reactions, poisoning of the reduction catalyst, and use of minimal amount of reactants.

Highly cross-linked imidazolium-based materials, obtained by radical oligomerization of bis-vinylimidazolium salts in the presence of 3-mercaptopropyl-modified silica gel, were used as supports for palladium catalysts. Thanks to the high imidazolium loading these materials were able to support a high amount of the metal (10 wt%). Such materials were characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer-Emmett-Teller technique, X-ray photoelectron spectroscopy, and transmission electron microscopy). The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compounds in high yields working with only 0.1 mol% of palladium loading at 50°C in ethanol/water under batch condition. Moreover, a flow apparatus, to optimize the efficiency of the isolation of the pure products and minimize waste (E-factor), was investigated. For the first time the palladium catalyst and base (K 2CO3) were placed in two separate columns allowing an easy recovery of the products with very low E-factor values (

Diels-Alder reactions of a range of 1-(alkoxy/alkyl/halogen-substituted phenyl)buta-1,3-dienes with methyl propiolate carried out in a green ethanolic medium under 9 kbar pressure were investigated. The use of high pressure as activating method of the Diels-Alder reactions allows efficient and regioselective generation of a series of cyclohexadienyl-benzene cycloadducts that are oxidized to the corresponding biaryls. The alkoxy/alkyl/halogen-substituted biaryls produced are useful precursors for accessing substituted 6H-benzo[c]chromen-6-ones and the cannabinols family.

Diels-Alder reactions of a range of 1-(alkoxy/alkyl-substituted phenyl)buta-1,3-dienes with methyl vinyl ketone and methyl acrylate carried out in ethanol as the reaction medium under 9 kbar pressure were investigated. The use of high pressure as the activating method of the Diels-Alder reactions allows the efficient and endodiastereoselective generation of a series of cis-cyclohexenyl-benzene cycloadducts, which are selectively converted into their trans-epimers. The cis-cyclohexenyl-benzenes and trans-cyclohexenyl-benzenes produced are useful precursors for accessing substituted privileged cis-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene and trans-6a,7,8,10a-tetrahydro-6H-benzo[c]chromene skeletons. The total syntheses of Δ(9)-cis-tetrahydrocannabinol (THC) and Δ(9)-trans-THC, through the use of selected Diels-Alder adducts, are described. Finally, a route for obtaining Δ(9)-trans-THC in both enantiomeric pure forms based on the (S)-(-)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP)-hydrazone method is also reported.

Diels-Alder cycloaddition reactions of 3-cyanocoumarin, hydroxy-substituted 3-cyanocoumarins and mesyl-substituted 3-cyano-coumarins with methyl-1,3-butadienes carried out under high pressure (11 kbar) are reported. Activation by high pressure allows these reactions to proceed satisfactorily under mild conditions to produce 6a-cyano-hydroxy- and 6a-cyano-mesyl-tetrahydro-6H-benzo[c]chromen-6-ones in moderate to excellent yield. The synthesis of cis-1-hydroxy-9-methyl-3-pentyl-6a,7,10,10a-tetrahydro-benzo[c]chromen-6-one as precursor of Delta(6)-3,4-cis-cannabidiol (Delta(6)-cis-CBD) and Delta(8)-cis-tetrahydrocannabinol (Delta(8)-cis-THC) is outlined.

We report herein a clean multistep flow process that starting from α,β-unsaturated ketones 1 allows the preparation of N-Boc-γ-amino alcohols 3 in high yields. The final products have been isolated in pure form without any additional purification step. The cleanness and environmental efficiency achieved using our protocol are proven by the calculation of green metrics such as E-factors.

In this contribution we have used green metrics analysis to compare the material efficiency, environmental impact, and safety-hazard impact in order to compare flow and batch procedures for azidation of α,β-unsaturated carbonyls. It has been proved that flow protocols possess a greener profile over the corresponding batch procedures based on identical chemistries. In this work the new flow procedure described is very efficient; however, the significant uncertainties in the environmental and safety-hazard impact scores are due to the lack of toxicity, hazard, and occupational exposure data available on trimethylsilyl azide and the resin catalysts used here. The results for the new flow procedure show significant and definite improvements over previously published work with respect to waste minimization/material efficiency and are consistent with satisfying green chemistry principles. The results obtained in this work prove the usefulness of our flow-approach for realizing highly efficient processes featuring minimal waste production.

An efficient protocol for the synthesis of β-amino acids starting from easily accessible α,β-unsaturated carboxylic acids based on the combination of two heterogeneous catalytic systems is reported. This multistep approach is based on the direct β-azidation of α,β-unsaturated carboxylic acids and subsequent azido group reduction performed in flow conditions. It has been demonstrated that the catalysts can be easily recovered and reused conserving its complete efficiency. The green metrics calculations proved the high environmental efficiency of the protocol characterized by very low waste production.

A new protocol for the Henry addition of nitroalkanes to aryl- and alkyl-aldehydes promoted by PS-BEMP under solvent-free conditions (SolFC) is presented. The corresponding nitroaldol products were obtained in good yields and short times; furthermore minimization of the reaction waste was achieved by reducing the use of organic solvents. Extension of the protocol was obtained by setting up the tandem Michael-Henry reaction of α,β-unsaturated aldehydes and nitroalkane to yield the corresponding dinitro derivatives.

γ-Valerolactone (GVL) can be a valid biobased replacement for toxic dipolar aprotic solvents especially in widely used cross-coupling reactions. In this contribution, we have proved that GVL can be a useful medium for the Hiyama reaction, and we developed a practical and efficient protocol for the Hiyama coupling using a nonexpensive and commercially available heterogeneous palladium catalyst without the use of any ligand or additive. Desired cross-coupling products 3a–m have been obtained in good to excellent yields (74–94%).

via azidolysis of epoxides under solvent-free conditions in the presence of a polystyrene-supported bisfluoride DABCO catalyst

3-Mercaptopropyl-modified silica-supported bis-imidazolium Pd-catalysts are developed and successfully utilized for Suzuki reactions.

Under solvent-free conditions the reaction of epoxides 1a–i with trimethylsilylazide (2) catalyzed by polystiryl-supported fluoride (PS-DABCOF2) has led to the efficient preparation of the corresponding O-TMS protected 1,2-azido alcohols 3a–i that, by treatment with Dowex-H, gave the related 1,2-azido alcohols 4a–i in excellent yields (83–99% and 82–96%, respectively). The use of a flow procedure has allowed us to significantly minimize waste in the preparation of representative 1,2-azido alcohols 4a, 4c and 4i that have been obtained with E-factors of 1.6, 2.1, and 1.9, respectively. The 1,2-amino alcohols 5a, 5c and 5f have been also prepared, in quantitative yields, by reduction of the corresponding O-TMS protected 1,2-azido alcohols 3a, 3c, and 3f by Pd on the Al2O3/HCOOH system.

Lewis acid catalyzed addition of butadienes to benzylideneacetones at high pressure allows an efficient access to arylated cyclohexenes.

High-pressure Diels-Alder reactions of various alkoxy/alkyl-substituted benzylideneacetones with methyl-1,3-butadienes are reported. Activation by high pressure (8-11 kbar) in combination with the mild Lewis acid HfCl(4).2THF allows these reactions to efficiently and regioselectively produce a series of ortho-substituted cyclohexenyl-benzene cycloadducts, that are useful precursors for the expeditious construction of the privileged 6,6-dimethyltetrahydro-6H-benzo[c]chromene skeleton. Application to the synthesis of Delta(8)-trans-THC in both enantiomeric pure forms is based on the successful resolution of selected cycloadduct by the SAMP-hydrazone method.

Diels−Alder cycloaddition reactions of 3-cyanocoumarin, hydroxy-substituted 3-cyanocoumarins and mesyl-substituted 3-cyano-coumarins with methyl-1,3-butadienes carried out under high pressure (11 kbar) are reported. Activation by high pressure allows these reactions to proceed satisfactorily under mild conditions to produce 6a-cyano-hydroxy- and 6a-cyano-mesyl-tetrahydro-6H-benzo[c]chromen-6-ones in moderate to excellent yield. The synthesis of cis-1-hydroxy-9-methyl-3-pentyl-6a,7,10,10a-tetrahydro-benzo[c]chromen-6-one as precursor of Δ6-3,4-cis-cannabidiol (Δ6-cis-CBD) and Δ8-cis-tetrahydrocannabinol (Δ8-cis-THC) is outlined.