Tandem Michael–anti-Michael Addition-Mediated Orthogonal Strapping of Diynones: Regioselective Spirocyclopentannulation of Oxindoles and Pyrazolones and DFT Validation

Abstract

An efficient protocol involving the transformation of sequentially generated recursive anions from heterocyclic precursors to orthogonally strap diynones through one pot transition-metal-free spirocyclopentannulation has been devised, employing oxindoles and pyrazolones as prototypical platforms. Insights into these regioselective tandem Michael–anti-Michael processes have been gleaned through DFT calculations.

Topology of electrostatic potential and electron density reveals a covalent to non-covalent carbon–carbon bond continuum

“…A transition state (TS) in a chemical reaction is essentially a configuration attained by reactants during complex formation where a local maximum value of the potential energy is obtained. Michael addition, 71–74 cycloaddition 75–77 and rearrangement 78–80 (Claisen, 81 Cope, 82 Wittig 78,83 etc. ) reactions usually exhibit TS that involve significant interaction between carbon atoms of reactants.…”

Concise Synthesis of Spirocyclic Dihydrophthalazines through Spiroannulation Reactions of Aryl Azomethine Imines with Cyclic Diazo Compounds

“…Among various spiroheterocyclic compounds, spiropyrazolones are well-known for their applications in pharmaceutical and coordination chemistry (Figure ). While a number of reliable methods for the preparation of spiropyrazolone derivatives have been disclosed, to our knowledge, the construction of a spiropyrazolonyl dihydrophthalazine scaffold has not been previously reported. Therefore, we were strongly motivated to carry out a systematic study on this serendipitously found reaction.…”

Coupling partner-dependent unsymmetrical C–H functionalization of N-phenoxyacetamides leading to sophisticated spirocyclic scaffolds

“…In addition, the introduction of spiro moieties often effectively alters the physicochemical and biological properties of parent compounds due to the high rigidity and unique three-dimensional geometries of spiro structures. Among various spiro scaffolds, spiropyrazolones 9 and spirooxindoles 10 are ubiquitous in natural products, pharmaceuticals, agrochemicals, dyes and chelating agents (Fig. 1).…”