Search for: All records

Density functional theory was used to elucidate the mechanism and the pericyclicity of chromium‐catalyzed bicyclization reactions that purportedly involve 8‐electron electrocyclization steps. Our computational results indicate that these reactions do indeed proceed via 8‐electron electrocyclization rather than an alternative pathway involving 4‐electron electrocyclization followed by Cope rearrangement. The role of C=[M] groups on the electrocyclization, specifically its pericyclicity, was examined in detail using modern theoretical tools.

Herein, we describe our synthetic efforts toward the pupukeanane natural products, in which we have completed the first enantiospecific route to 2‐isocyanoallopupukeanane in 10 steps (formal synthesis), enabled by a key Pd‐mediated cyclization cascade. This subsequently facilitated an unprecedented bio‐inspired “contra‐biosynthetic” rearrangement, providing divergent access to 9‐isocyanopupukeanane in 15 steps (formal synthesis). Computational studies provide insight into the nature of this rearrangement.

A site‐selective C(3)/C(4)‐alkylation ofN‐pyridylisoquinolones is achieved by employing C−C bond activation of cyclopropanols under Ru(II)‐catalyzed/Cu(II)‐mediated conditions. The regioisomeric ratios of the products follow directly from the electronic nature of the cyclopropanols and isoquinolones used, with electron‐withdrawing groups yielding predominantly the C(3)‐alkylated products, whereas the electron‐donating groups primarily generate the C(4)‐alkylated isomers. Density functional theory calculations and detailed mechanistic investigations suggest the simultaneous existence of the singlet and triplet pathways for the C(3)‐ and C(4)‐product formation. Further transformations of the products evolve the utility of the methodology thereby yielding scaffolds of synthetic relevance.

The template‐directed C−H insertion of α,β‐unsaturated esters into quinoline was interrogated by using computational quantum chemistry. An energetically viable mechanism for this complex multistep transformation was elucidated, with attention paid throughout to conformational flexibility and alternative ligand binding modes. The selectivity was found to correlate with distortion from a tetrahedral geometry for the carbon atom involved in C−H insertion, a parameter that can be applied to future template design.

The [3s,5s]‐sigmatropic shift is an example of an orbital‐symmetry forbidden pericyclic reaction that is outcompeted by the allowed [3s,3s]‐sigmatropic shift. Density functional theory calculations are used to show that Pd^II‐complexed systems with strategically placed substituents engaging in key stereoelectronic effects can select for the [3s,5s] process, thereby outcompeting both orbital‐symmetry‐allowed [3s,3s]‐ and [3s,5a]‐shifts.

The [3s,5s]‐sigmatropic shift is an example of an orbital‐symmetry forbidden pericyclic reaction that is outcompeted by the allowed [3s,3s]‐sigmatropic shift. Density functional theory calculations are used to show that Pd^II‐complexed systems with strategically placed substituents engaging in key stereoelectronic effects can select for the [3s,5s] process, thereby outcompeting both orbital‐symmetry‐allowed [3s,3s]‐ and [3s,5a]‐shifts.