Overcoming Kinetic and Thermodynamic Challenges of Classic Cope Rearrangements.

Systematic evaluation of 1,5-dienes bearing 3,3-electron-withdrawing groups and 4-methylation results in the discovery of a Cope rearrangement for Meldrum's acid-containing substrates that have unexpectedly favorable kinetic and thermodynamic profiles. The protocol is quite general due to a concise and convergent synthesis from abundant starting materials. Furthermore, products with an embedded Meldrum's acid moiety are prepared, which, in turn, can yield complex amides under neutral conditions. We have now expanded the scope of the reductive Cope rearrangement, which, via chemoselective reduction, can promote thermodynamically unfavorable [3,3] sigmatropic rearrangements of 3,3-dicyano-1,5-dienes to form reduced Cope rearrangement products. The Cope rearrangement is found to be stereospecific and can yield enantioenriched building blocks when chiral, nonracemic 1,3-disubstituted allylic electrophiles are utilized. We expand further the use of Cope rearrangements for the synthesis of highly valuable building blocks for complex- and drug-like molecular synthesis.

Bis[1-(2-eth-oxy-phen-yl)-3-(4-nitro-phen-yl)triazenido]mercury(II).

In the title compound, [Hg(C(14)H(13)N(4)O(3))(2)], the central Hg atom (site symmetry 2) is six-coordinated by two tridentate 1-(2-eth-oxy-phen-yl)-3-(4-nitro-phen-yl)triazenide ligands through two N and one O atoms. The mononuclear complex mol-ecules are connected into two parallel chains by inter-molecular C-H⋯O hydrogen-bonding inter-actions. These chains are connected to each other by face-to-edge C-H⋯π inter-actions between the CH of the ethoxy groups and the aromatic rings, resulting in a two-dimensional architecture in the ac plane.

Transient [3,3] Cope rearrangement of 3,3-dicyano-1,5-dienes: computational analysis and 2-step synthesis of arylcycloheptanes.

A simple and modular route to arylcycloheptene scaffolds is reported. The two-step route from Knoevenagel adducts and allylic electrophiles is made possible through the design of a Cope rearrangement that utilizes a "traceless" activating group to promote an otherwise thermodynamically unfavorable transformation. Experimentally, the [3,3] rearrangement occurrs transiently at room temperature with a computed barrier of 19.5 kcal mol-1, which ultimately allows for three-component bis-allylation. Ring-closing metathesis delivers the arylcycloheptane and removes the activating group. This report describes the design and optimization of the methodology, scope and mechanistic studies, and computational analysis.

Factors Governing and Application of the Cope Rearrangement of 3,3-Dicyano-1,5-dienes and Related Studies.

Cope and co-workers reported the [3,3] rearrangement of 3,3-dicyano-1,5-dienes in the early 1940s ("The Cope rearrangement"). However, these original substrates have remained largely unstudied until recently. Herein we explore styrene-deconjugating Cope rearrangements, a diastereoselective Cope rearrangement/deconjugative α-allylation sequence, and factors governing α- vs γ-allylation regioselectivity of Knoevenagel adduct allyl anions. Ultimately, these studies result in the synthesis of diverse and functionally dense polycycloalkane frameworks from abundant reagents using simple chemistry.

One-pot synthesis, FT-IR and density functional method (DFT) studies on N-benzyl-N-ethyl-N-[5-nitro-2-(1,1,3,3-Tetramethylbutylamino)-1-benzofuran-3-yl]amine.

N-benzyl-N-ethyl-N-[5-nitro-2-(1,1,3,3-Tetramethylbutylamino))-1-benzofuran-3-yl]amine, 7, was synthesized and characterized by elemental analysis, FT-IR, (1)H and (13)C NMR spectra. The geometrical structures, vibrational frequencies, and molecular electrostatic potential (MEP) of 7 in the ground state were calculated by using the DFT/B3LYP method with 6-31 G(d) basis set. The optimized structure was compared with analogous compound. The IR spectrum of 7 was interpreted in terms of potential energy distribution (PED) analysis. Comparison of the experimental vibrational spectra of 7 with the theoretical data indicated good agreement.

Prediction of capillary gas chromatographic retention times of fatty acid methyl esters in human blood using MLR, PLS and back-propagation artificial neural networks.

Quantitative structure-retention relationship (QSRR) models correlating the retention times of fatty acid methyl esters in high resolution capillary gas chromatography and their structures were developed based on non-linear and linear modeling methods. Genetic algorithm (GA) was used for the selection of the variables that resulted in the best-fitted models. Gravitational index (G2), number of cis double bond (NcDB) and number of trans double bond (NtDB) were selected among a large number of descriptors. The selected descriptors were considered as inputs for artificial neural networks (ANNs) with three different weights update functions including Levenberg-Marquardt backpropagation network (LM-ANN), BFGS (Broyden, Fletcher, Goldfarb, and Shanno) quasi-Newton backpropagation (BFG-ANN) and conjugate gradient backpropagation with Polak-Ribiére updates (CGP-ANN). Computational result indicates that the LM-ANN method has better predictive power than the other methods. The model was also tested successfully for external validation criteria. Standard error for the training set using LM-ANN was SE=0.932 with correlation coefficient R=0.996. For the prediction and validation sets, standard error was SE=0.645 and SE=0.445 and correlation coefficient was R=0.999 and R=0.999, respectively. The accuracy of 3-2-1 LM-ANN model was illustrated using leave multiple out-cross validations (LMO-CVs) and Y-randomization.