Efficient Synthesis of 3-Aryl-5-chloroindan-1-ones via Free Radical–Mediated Intramolecular Cyclization

An efficient free radical–mediated intramolecular cyclization strategy has been developed for the synthesis of 3-aryl-5-chloroindan-1-ones. Variously substituted 2,4-dichloroenones afforded 3-aryl-5-chloroindan-1-ones in quantitative yields upon intramolecular cyclization under free radical conditions.     

Synthesis of 5-iodo-1,2,3-triazole-containing macrocycles using copper flow reactor technology

A new macrocyclization strategy to synthesize 12- to 31-membered 5-iodo-1,2,3-triazole-containing macrocycles is described. The macrocycles have been generated using a simple and efficient copper-catalyzed cycloaddition in flow under environmentally friendly conditions. This methodology also permits the facile, regioselective synthesis of 1,4,5-trisubstituted-1,2,3-triazole-containing macrocyles using palladium-catalyzed cross-coupling reactions.     

New and clean strategy for the determination of Cu2+ in electroless copper plating baths

This article concerns a new and clean strategy for the determination of Cu(2+) in electroless copper plating baths with differential spectrophotometry. With this strategy, the problem of too high absorbance of Cu(2+) under plating conditions has been solved. We investigated the influence of copper sulfate, sodium hypophosphite, nickel sulfate, sodium citrate, polyglycol, temperature and pH on the absorption spectrum of Cu(2+) in electroless copper plating baths. Five grams per litre of CuSO(4).5H(2)O solution was selected as the reference solution. Experimental results prove that, this strategy has the merits of fast and high accuracy compared to the traditional techniques. Linearly dependent coefficient of the working curve is 0.9999 and the components in the formula have no obvious effect on the detection of Cu(2+) under experimental conditions. Therefore, we can directly move solutions from the EC plating baths for detection, after that the sample can still go back to the baths without any pollution from the plating process to the environment.     

Tandem Prins cyclization for the synthesis of 1,8-dioxa-3-azaspiro[4.5]dec-2-ene derivatives

A tandem Prins strategy has been developed for the synthesis of 1,8-dioxa 3-azaspiro[4.5]dec-2-ene derivatives using 5?mol% Cu(OTf)₂ in dichloromethane at 0?°C under mild reaction conditions in short reaction times. This method provides the products in good yields with a diverse substitution pattern.     

Strategy for the chiral separation of non-acidic pharmaceuticals using capillary electrochromatography

In completion of an earlier defined generic chiral screening approach, a generic separation strategy for basic, bifunctional, and neutral compounds was proposed and evaluated. This strategy adds to a previously defined strategy for acidic compounds. The screening experiment of the actual strategy used a mobile phase of 5 mM phosphate buffer pH 11.5/ACN (30/70 v/v), a temperature of 25 degrees C, and a voltage of 15 kV. The selected chiral stationary phases were Chiralpak AD-RH, Chiralcel OD-RH, Chiralcel OJ-RH, and Chiralpak AS-RH, all based on polysaccharide selectors. It was seen that 31 out of 48 test compounds were partially or baseline-resolved under screening conditions. After execution of the optimization steps of the strategy, this number increased to 41, with a total of 21 baseline-separated compounds. Combined with the results obtained from the acidic test set examined in the earlier defined strategy, of all tested compounds 82.5% showed enantioselectivity and 49.2% could be baseline-separated.     

An efficient synthesis of brominated 4-alkyl-2(5H)-furanones

A versatile method for the synthesis of novel brominated 4-alkyl-2(5H)-furanones under mild reaction conditions is described. This synthetic strategy requires only one chromatographic separation over six steps and employs the cyclodehydration of brominated levulinic acid as the key transformation.     

Retention of chirality of 5-membered alicyclic α-amino acids bearing N-(2-phenyl)benzoyl group in photoinduced decarboxylative intermolecular radical addition to acrylonitrile

Photoinduced decarboxylative radical additions of 5-membered alicyclic α-amino acids bearing a (2-phenyl)benzoyl protective group to acrylonitrile under mild organic photoredox catalysis conditions furnished γ-amino acid derivatives with high retention of chirality via the memory of chirality (MOC) strategy. The retention of chirality in the photoinduced decarboxylation was strongly dependent on the structure of the alicyclic α-amino acids and alkenes. To the best of our knowledge, this is the first example of the decarboxylative intermolecular radical addition to alkenes with retention of chirality at the position of radical generation using the MOC strategy.     

Synthesis of Novel Rigid Analogs of Tryptamine as Potential Serotonin Ligands through Pd(0)-Catalyzed Diaryl Coupling Reactions

A series of novel tetracyclic 6-thia-5a-aza-acephenanthrylene derivatives 7 were synthesized by rigidization of the arylsulfonyl/carbonyl/methyl moiety through C7 of indole, which was achieved under Heck conditions. The strategy of altering the palladium–bromine exchange site produced target products.     

Three‐Component Synthesis of Spiro[indoline‐3,4′‐pyrazolo[3,4‐b]pyridines] under Microwave Irradiation

A domino three‐component strategy with high efficiency for the synthesis of spiro[indoline‐3,4′‐pyrazolo[3,4‐b ]pyridines] from easily available isatins, pyrazol‐5‐amines and β‐ketonitriles under microwave heating. During reaction process, HOAc plays dual roles as reaction media as well as a Brønsted acid‐promoter. Flexible structural modification, broad functional group compatibility and mild reaction conditions make this strategy a useful and attractive process of library generation for drug discovery.     

Intermolecular Electronic Coupling of Organic Units for Efficient Persistent Room‐Temperature Phosphorescence

Although persistent room‐temperature phosphorescence (RTP) emission has been observed for a few pure crystalline organic molecules, there is no consistent mechanism and no universal design strategy for organic persistent RTP (pRTP) materials. A new mechanism for pRTP is presented, based on combining the advantages of different excited‐state configurations in coupled intermolecular units, which may be applicable to a wide range of organic molecules. By following this mechanism, we have developed a successful design strategy to obtain bright pRTP by utilizing a heavy halogen atom to further increase the intersystem crossing rate of the coupled units. RTP with a remarkably long lifetime of 0.28 s and a very high quantum efficiency of 5 % was thus obtained under ambient conditions. This strategy represents an important step in the understanding of organic pRTP emission.     

Accelerating the thermal fading rate of photochromic naphthopyrans by pillar[5]arene-based conjugated macrocycle polymer

A new micro-spherical conjugated macrocycle polymer (P[5]-TFB-CMP) was prepared by the condensation reaction between dihydrazide functionalized pillar[5]arene and 1,3,5-triformylbenzene under ambient conditions. P[5]-TFB-CMP exhibits large surface area with excellent thermal stability and has been used as additive to prepare composite PMMA film of photochromic naphthopyrans. The results showed that the addition of P[5]-TFB-CMP could dramatically accelerate the thermal fading rate of the photochromic composite film by up to 12 times. This is a new strategy to overcome the drawback of the matrix effect.     

Iodine-catalyzed synthesis of 5-benzoyl-8H-phthalazino[1,2-b]quinazolin-8-one derivatives via a domino reaction involving a benzyl automatic oxidation by oxygen

A one-pot procedure for the synthesis of 5-benzoyl-8H-phthalazino[1,2-b]quinazolin-8-ones is achieved by an iodine-catalyzed reaction of 2-aminobenzohydrazides and 2-alkynylbenzaldehydes in good yields. The salient feature of this strategy is a domino type process including a condensation, addition, hydroamination, and a noteworthy benzyl automatic oxidation by oxygen under metal-catalyst-free conditions.     

Concise total synthesis of (±)-cephalotaxine via a transannulation strategy: development of a facile reductive oxy-Nazarov cyclization

A concise total synthesis of (±)-cephalotaxine (1) has been achieved from dioxolanone derivative 15 via a transannulation strategy. The key transformation is a facile reductive oxy-Nazarov cyclization as illustrated above, involving presumably a tethered 1,2-oxidopentadienyl cation species 7a or 7b, which represents a new variant of the oxy-Nazarov cyclization and constitutes an effective, regio- and stereospecific 5-hydroxy cyclopentenone annulation protocol under mild hydride reduction conditions.     

TFA promoted multi-component reaction of aryldiazonium with sodium metabisulphite and thiols: Construction of thiosulfonate under transition-metal free conditions

A TFA promoted multi-component reaction of aryldiazonium with sodium metabisulphite and thiols to construct thiosulfonates under transition-metal free conditions is reported. The thiosulfonates were isolated in good yields with broad tolerance of functional group. Readily available inorganic Na₂S₂O₅ was applied as the sulfur dioxide surrogate. This strategy features easily available substrates, mild reaction conditions and free transition-metal catalyst.     

Effect of Heating Strategy on Power Consumption and Performance of a Pilot Plant Anaerobic Digester

The effect of heating strategy on power consumption and performance of a pilot plant anaerobic digester treating chicken litter, under thermophilic conditions, has been studied. Heating strategy was evaluated using three different spans (0.2 °C, 0.6 °C, and 1.0 °C) for triggering the temperature control system from target temperature (56.7 °C). The hydraulic retention time in the pilot plant digester was in the range of 32 to 37 days, varying the total solids concentration fed from 5% to 6%. The results showed that under the experimental conditions, heating was the most energy-demanding process with 95.5% of the energy used. Increments up to 7.5% and 3.8%, respectively, on mechanical and heating power consumption, were observed as the span, for triggering the temperature control system from target temperature, was increased. Under the experimental conditions studied here, an increment of 30.6% on the global biodigester performance index was observed when a span of 1.0 °C was compared to the one of 0.2 °C.     

Total synthesis of verbalactone: an efficient, carbohydrate-based approach

A carbohydrate-based strategy for the total synthesis of verbalactone has been described. (3R,5R)-3,5-dihydroxydecanoic acid was dimerised under Yamaguchi conditions to provide verbalactone in an overall yield of 17% starting from 3-deoxy-1,2:5,6-di-O-isopropylidine-α-d-glucofuranose.     

Alkylation of aryl 3-oxopropanedithioate and 3-amino-1-aryl-3-thioxo-1-propanones as an effective tool for the construction of differently substituted thiophenes and annulated thiophenes

The alkylation of aryl 3-oxopropanedithioate with α-haloketones under different reaction conditions afforded substituted aryl[2-(methylsulfanyl)-4-phenyl-3-thienyl]methanones and [3-aryl-5-(methylsulfanyl)-2-thienyl](phenyl)methanones. The same strategy was extended to 3-amino-1-aryl-3-thioxo-1-propanones to afford aryl[2-amino-4-phenyl-3-thienyl]methanones and ethyl 3-phenyl-5-piperidino-2-thiophene carboxylate.     

Chiral lithium amide base-mediated rearrangement of meso-cyclohexene oxides: asymmetric synthesis of amino- and aziridinocyclohexenols

Two different chiral lithium amide base routes for the synthesis of amino- and aziridino-containing cyclohexenols have been explored. The first strategy involved the diastereoselective preparation of novel meso-aziridinocyclohexene oxides and their subsequent enantioselective rearrangement using chiral bases. In this approach, the diphenylphosphinoyl nitrogen protecting group proved optimal and aziridinocyclohexenols of 47-68% ee were obtained. Of particular note was the smooth rearrangement of the epoxide to an allylic alcohol in the presence of an aziridine: under optimised chiral base conditions, the aziridine remained essentially unaffected. A second more straightforward strategy for introduction of an amino functionality was also investigated: (1S,4R,5S)- and (1R,4R,5S)-4,5-bis(tert-butyldimethylsilyloxy)cyclohex-2-enols, readily prepared in > 95% ee using a chiral base approach, were subjected to Mitsunobu substitution using a sulfonamide and Overman rearrangement.     

Easy saponification by metal silanolates: application in SPPS and in (S)-5-hydroxynorvaline preparation

Alkali metal trimethylsilanolates, TMSO⁻, M⁺, has been used for efficient conversion of methyl esters into their corresponding anhydrous acid salts under mild non-aqueous conditions. This strategy has been applied to SPPS for the preparation of neurotoxin cyclic analogues and in (S)-5-hydroxynorvaline synthesis.     

New strategy for the synthesis of 3',5'-bifunctionalized oligonucleotide conjugates through sequential formation of chemoselective oxime bonds

A convenient strategy for the synthesis of bifunctionalized oligonucleotide conjugates bearing two different reporters at the 3' and 5' ends of the oligonucleotide is presented. The method involves the preparation of oligonucleotides bearing an aldehyde and/or aminooxy functionality at each end, followed by reaction to form oxime bonds with appropriately functionalized reporters. The conjugation reactions are carried out under mild aqueous conditions with good reaction yield.