The phenomenon of conservative-perturbed equilibrium in conditions different reactors

Finding the optimal mode is a conceptual problem. The most important indicator that reflects the perfection of a chemical reactor is the intensity of the process in it. The phenomenon of conservatively perturbed-equilibrium (CPE) in the conditions of different types of reactors (in acyclic and cyclic systems) was studied: the ideal displacement reactor ("steady-state plug flow reactor, PFR") and the ideal mixing reactor ("steady-state continuous stirred tank reactor, CSTR"). For the acyclic reaction, the time of extremum onset was less in CSTR by ≈2.1%, but the concentration of substance B in the extremum in PFR was greater by ≈17.2% than in CSTR. For the cyclic reaction, the time of extremum onset was less in CSTR by ≈5.6%, but the concentration of substance B in the extremum in PFR was greater by ≈11.6% than in CSTR. For the acyclic and cyclic reaction in PFR, the time of occurrence of the extremum of the cyclic reaction was lower by ≈44.2% than in the acyclic, but the concentration of substance B in the extremum of the acyclic reaction was greater by ≈24.8% than in the cyclic reaction. For the acyclic and cyclic reaction in CSTR, the time of occurrence of the extremum of the cyclic reaction was lower by ≈46.2% than in the acyclic, but the concentration of substance B in the extremum in the acyclic reaction was greater by ≈18.9% than in the cyclic reaction. The cyclic system showed a shorter time for the onset of the extremum, but the acyclic reaction system showed a higher concentration of substance B at the extremum in PFR and CSTR. Although the time of extremum onset was the lowest in CSTR in the cyclic system, the concentration of substance B in the extremum was highest in the PFR in the acyclic system. Therefore (from our systems and reactors) the acyclic system in PFR shows the best characteristics. The extremum in transient modes is always observed for acyclic and cyclic complex reactions in both reactors, both in PFR and in CSTR. The phenomenon of conservatively perturbed-equilibrium is manifested in both PFR and CSTR. With the same rate constants, the acyclic system in PFR is characterized by higher values of "over equilibrium" conversion than the acyclic system in CSTR. Similarly, with the same rate constants, the cyclic system in PFR is characterized by higher values of "over equilibrium" conversion than the cyclic system in CSTR. The time of extremum onset is less in CSTR. This is true for acyclic and cyclic systems. The greater the difference between the initial concentrations of the two substances, the greater the "over equilibrium" concentration of the third substance, the initial concentration of which was equilibrium. At our values of kinetic parameters, the sensitivity of the time of occurrence of the extremum of the same reaction in different reactors (PFR and CSTR) is small (up to ≈5.6%), and at different reactions (acyclic and cyclic), but in one type of reactor (PFR or CSTR) - significant, reaching ≈46.2%.

Cascade intramolecular rearrangement/cycloaddition of nitrocyclopropane carboxylates with alkynes/alkenes: access to uncommon bi(hetero)cyclic systems

A straightforward approach for the one-pot synthesis of fused bi(hetero)cyclic systems via cascade intramolecular rearrangement/cycloaddition reaction of nitrocyclopropane carboxylates with substituted alkynes/alkenes has been demonstrated.

Small rings in the bigger picture: ring expansion of three- and four-membered rings to access larger all-carbon cyclic systems

Ring-expansion of strained small-size rings to forge larger all-carbon ones, allows a rapid build-up of molecular complexity.

Gold Catalysis of Non-Conjugated Haloacetylenes

Gold-catalyzed reactions of conjugated haloacetylenes are well known and usually result in the formation of addition or dimerization products. Herein, we report a gold-catalyzed reaction of non-conjugated­ haloacetylenes, which leads exclusively to the halogenated cyclization products. Remarkable is the gold-catalyzed reaction of tritylhaloacetylenes to haloindene derivatives, as mechanistic studies reveal that an 1,2-aryl shift occurs in the initially formed gold complex. The potential functionalization at the halogen atom and the wide scope of these cyclization reactions make them an attractive method for the construction of cyclic systems.

Chemical Synthesis of Acyclic Nucleoside Phosphonate Analogs Linked with Cyclic Systems between the Phosphonate and the Base Moieties

The syntheses of acyclic nucleoside phosphonate (ANP) analogs linked with cyclic systems are described in the present review. The purpose of the review is to report the methodology of ANP analogs and to give an idea on the synthesis of a therapeutic structural feature of such analogs. The cyclopropane systems were mainly prepared by diazomethane cyclopropanation catalyzed by Pd(OAc)2, intramolecular alkylation, Kulinkovich cyclopropanation, and use of difluorocyclopropane, and so forth. The preparation of methylenecyclopropane system was made by diazoacetate cyclopropanation catalyzed by Rhodium followed by addition-elimination reactions. For the preparation of a variety of tethered 1,2,3-triazole systems, 1,3-dipolar cycloaddition between azidealkylphosphonates and propargylated nucleobases was mainly applied. The formation of various phosphonate moieties was achieved via phosphonylation of alkoxide, cross-coupling between BrZnCF2P (O)(OEt)2 with iodoalkens catalyzed by CuBr, Michaelis-Arbuzov reaction with phosphite, and Rh(II)-catalyzed O-H insertion, and so forth.