In the syntheses developed to access naturally occurring compounds, especially bioactive substances, boron-functionalized dienes (also "linchpin" reagents) are used as key reagents. Structurally unique dienes are found in nature, and play important biological and chemical roles. Recently, linchpin moieties have been proved as useful substrates for a variety of highly functionalized chemical transformations. The products of these processes are potentially of some use for the syntheses of an important class of natural products showing a wide range of biological activities. This review describes progress in the synthesis of borylsubstituted buta-1,3-dienes as well as their application in organic chemistry.

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A facile ruthenium‐catalyzed regio‐ and stereoselective hydroboration of symmetrical, aromatic 1,3‐diynes with pinacolborane towards 2‐boryl‐1,4‐diaryl‐buta‐1‐en‐3‐ynes and their further transformation into potassium trifluoroborate salts is presented. The reaction proceeded efficiently for 1,4‐diphenylbutadiynes with various substituents on the phenyl rings and heterocyclic 1,4‐di(thiophen‐3‐yl)buta‐1,3‐diyne. The resulting products were isolated and fully characterized (1H, 13C, 11B and 1D NOESY NMR, IR, GC‐MS, HRMS or elemental analysis). Moreover, the crystal structure of an enynyl boronate was determined, proving the addition of boryl moiety at the internal carbon in the diyne, according to the anti‐Markovnikov rule. The results presented here are the first examples of selective catalytic monohydroboration of conjugated diynes. The products obtained due to the presence of the boryl group and the unsaturated bonds are potential synthons in the synthesis of natural compounds or active pharmaceutical ingredients (API). The model Suzuki coupling of 2‐boryl‐1,4‐diphenyl‐buta‐1‐en‐3‐ynes with iodobenzene was carried out to illustrate the utility of the resulting compounds.

A facile method for the synthesis of unsaturated organoboron compounds by hydroboration of terminal and internal alkynes in supercritical (sc) CO2 has been presented for the first time. The reactions performed in scCO2 in the presence of Ru catalysts (selectivity, productivity) are compared with those in a traditionally used solvent or without it. Moreover, the catalytic systems based on the application of scCO2 have been successfully tested for the processes under repetitive batch conditions. This strategy permitted us to obtain boryl‐substituted olefins with high yields and selectivities up to the 16th catalytic cycle if using Ru(CO)Cl(H)(PPh3)3 as a catalyst. The process applied the self‐dosing catalyst, which is gradually released to the reaction mixture under supercritical conditions in the individual batch. Such an approach has a positive impact on process sustainability and economy.

A new stereoselective method for the synthesis of (E)-β-arylvinyl iodides and (E)- or (Z)-β-arylvinyl bromides from styrenes and vinyl boronates on the basis of a one-pot procedure via borylative coupling/halodeborylation is reported. Depending on the halogenating agent as well as the mode of the halodeborylation reaction, (E) or (Z) isomers are selectively formed.

SUMMARY Usually marine algae are an excellent source of pigments for different commercial sectors. Freshwater macroalgae can be exploited as a good source of biologically active compounds provided an appropriate extraction method is developed. The efficiency of four methods, like microwave‐assisted (MAE), ultrasound‐assisted extraction (UAE), supercritical fluid extraction (SFE) with ethanol as a co‐solvent, as well as conventional Soxhlet extraction were studied in the same conditions (time, solvent and temperature) for the recovery of chlorophylls and carotenoids from three freshwater green algae species: Cladophora glomerata, Cladophora rivularis and Ulva flexuosa. UV‐Vis spectrophotometry was used to determine chlorophyll a, chlorophyll b and total carotenoid content in obtained extracts. The results of this study showed that the advantages of novel extraction techniques (MAE and UAE) include higher yield and, in consequence, lower costs compared to traditional solvent extraction techniques. These methods were much more efficient in freshwater green algae pigment recovery than the classic Soxhlet extraction as well as SFE.

This paper reports on the first detailed studies on green and sustainable methods for the repetitive batch hydroboration of terminal and internal alkynes by the effective immobilization of Ru­(CO)­Cl­(H)­(PPh3)3 in various ionic liquids (RuH@IL) or in biphasic ionic liquid/supercritical CO2 (RuH@IL/scCO2) systems. The systems RuH­(1 mol %)@[EMPyrr]­[OTf]­(IL8) and RuH­(1 mol %)@[EMPyrr]­[NTf2]­(IL9) were found to be the most effective immobilization approaches, with both allowing the completion of over 10 complete catalytic cycles in the hydroboration of a series of different alkynes. An increase in the catalyst content to 2 mol % (RuH­(2 mol %)@[EMPyrr]­[NTf2]­(IL9)) allowed for the completion of 25 repetitive batches, which proved the high utility of the developed system. In each case, high yields of products were obtained, and their purity was confirmed through NMR, MS, and ICP techniques. On the other hand, the use of RuH­(1 mol %)@/[EMPyrr]­[OTf]­(IL8)/scCO2 in the hydroboration of phenylacetylene with pinacolborane, permitted effective completion of 8 cycles, at a much lower temperature than that at which RuH@IL was used (40 vs 100 °C). Moreover, the application of such a system has a positive impact on the environment and process sustainability via the exchanging of organic solvent for scCO2 used for product extraction and separation when working with RuH@IL. The strategies presented in this work are, so far, the most effective and recyclable systems based on ILs for the hydroboration of alkynes with high TONs. In the future, they will be applied in continuous flow regime.

An efficient method has been successfully developed for the functionalization of various 1,3-diynes by the hydrosilylation reaction with triethyl- or triphenylsilane catalyzed by Pt catalysts (Pt2(dvs)3, PtO2, or Pt­(PPh3)4). Comprehensive optimization studies were performed for the first time to find suitable process conditions for the stereo- and regioselective formation of mono- or bis-silylated adducts from commercially available substrates and catalysts. Silyl-substituted 1,3-enynes or bis-silyl-functionalized buta-1,3-dienes were obtained with excellent yields and fully characterized.