A last-in first-out stack data structure implemented in DNA

DNA-based memory systems are being reported with increasing frequency. However, dynamic DNA data structures able to store and recall information in an ordered way, and able to be interfaced with external nucleic acid computing circuits, have so far received little attention. Here we present an in vitro implementation of a stack data structure using DNA polymers. The stack is able to record combinations of two different DNA signals, release the signals into solution in reverse order, and then re-record. We explore the accuracy limits of the stack data structure through a stochastic rule-based model of the underlying polymerisation chemistry. We derive how the performance of the stack increases with the efficiency of washing steps between successive reaction stages, and report how stack performance depends on the history of stack operations under inefficient washing. Finally, we discuss refinements to improve molecular synchronisation and future open problems in implementing an autonomous chemical data structure.

[DBN][HSO4]-Promoted facile and green synthesis of 2-Amino-4H-pyrans derivatives under microwave irradiation

The [DBN][HSO4] -promoted Knoevenagel condensation followed by cyclization protocol has been developed for the first time by a successive reaction of aldehydes, dimedone and malononitrile to afford 2-Amino-4H-pyrans derivatives in high to excellent yields at room temperature. The synergic couple of microwave and ionic liquid provided the capability to allow a variability of functional groups, short reaction times, easy workup, high yields, recyclability of the catalyst, and solvent-free conditions, thus providing economic and environmental advantages. Keywords: [DBN][HSO4], Environmentally benign, 2-Amino-4H-pyrans, Knoevenagel condensation, Microwave irradiation

Catalyst Performance in the HDPE Pyrolysis-Reforming under Reaction-Regeneration Cycles

The performance of a Ni commercial catalyst has been studied under reaction-regeneration cycles in a continuous process consisting of the flash pyrolysis (500 °C) of high-density polyethylene (HDPE) in a conical spouted bed reactor (CSBR), followed by catalytic steam reforming in-line (700 ºC) of the volatiles formed in a fluidized bed reactor. The catalyst is regenerated between reactions by coke combustion in situ in the reforming reactor, using a sequence of air concentrations and following a temperature ramp between 600 and 700 °C. Several analytical techniques (TPO, TEM, XRD, and TPR) have proven that the catalyst does not fully recover its initial activity by coke combustion due to the sintering of Ni0 active sites. This sintering process is steadily attenuated in the successive reaction-regeneration cycles and the catalyst approaches a steady state.

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

A unique 1,7-S- and Se-shift reaction under Pummerer reaction conditions of 4-alkenyl-3-sulfinyl- and seleninylpyrroles was described. The usual Pummerer reaction of 4-(alkenylaminomethyl)-3-phenylsulfinylpyrroles and a successive reaction with tetrabutylammonium hydroxide (TBAH) yielded either pyrrolo[3,2-c]azepines or N-pyrrol-3-ylmethyl-N-(4-hydroxy-3-sulfanylpropyl)-p-toluenesulfonamides (diols). Seleno-Pummerer reactions of 3-selanylmethylpyrroles also proceeded via in situ generation of selenoxides, followed by a treatment with TBAH.

Operando XAS/Raman/MS monitoring of ethanol steam reforming reaction–regeneration cycles

The catalyst regeneration leads to the redispersion of smaller cobalt particles leading to a similar conversion along successive reaction–regeneration cycles.

Transition-metal-free one-pot synthesis of alkynyl selenides from terminal alkynes under aerobic and sustainable conditions

Alkynyl selenides were synthesized by a straightforward one-pot and three-step methodology, without the need of diselenides as starting reagents, under an oxygen atmosphere and using PEG 200 as the solvent. This procedure involves the in situ generation of dialkyl diselenides through a K3PO4-assisted reaction of an alkyl selenocyanate obtained by a nucleophilic substitution reaction between KSeCN and alkyl halides. Successive reaction with terminal alkynes in the presence of t-BuOK affords the corresponding alkyl alkynyl selenide in moderate to good yields. Finally, this methodology allowed the synthesis of 2-alkylselanyl-substituted benzofuran and indole derivatives starting from convenient 2-substituted acetylenes.

Recent advances in organic reactions catalyzed by graphene oxide and sulfonated graphene as heterogeneous nanocatalysts: a review

Over the past decade, the application of carbocatalyst systems has been preferred over that of homogeneous catalytic systems because of their advantages such as physical and thermal stability of the catalysts in successive reaction runs and reusability.

Synthesis of Ropivacaine under Ultrasound Irradiation

Ropivacaine hydrochloride was synthesized from 2-pipecolic acid by successive reaction with SOCl2 and 2,6-dimethylaniline at 40°C under ultrasonic irradiation to give (S)-N-(2,6-dimethylphenyl)-piperidin-2-carboxamide (4), and 4 was reacted with 1-bromopropane at 50°C for 1 h under ultrasonic irradiation. The effect of reaction solvent, temperature and time under ultrasonic irradiation were investigated. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields. The total yield was 63.1%, [α]25 D= – 6.7°(c = 2, H2O).