Ring Opening of 1,1’-sulfonyl bis-aziridines Derived from L-Amino Acids and DFT Study on their Affinity Toward Different Nucleophiles

: We describe herein the ring-opening reaction of chiral 1,1’-sulfonyl bis-aziridines with various neutral and anionic nucleophiles, including benzylamine, piperidine, acetate, allyl thiolate, cyanide anion, and sodium ethoxide. These reactions afforded bis-opened or/and mono-opened compounds via a regioselective attack on the non-substituted methylene of aziridine ring. The structures of the products were confirmed based on spectral analysis (IR, 1H NMR, and 13C NMR). A theoretical study involving density functional theory (DFT) was used to rationalize the region-selective ring-opening of starting bis-aziridines.

Selective Ring Opening Allene Metathesis: Polymerization or Ruthenium Vinylidene Formation

Selective ring-opening allene metathesis polymerization (ROAlMP) and ruthenium vinylidene formation from 1,2-cyclononadiene (<b>1</b>) by simple catalyst selection are discussed. Grubbs second generation catalyst (G2) favors the formation of an alkylidene leading to the ROAlMP of (<b>1</b>). Grubbs first generation catalyst (G1) favors vinylidene formation and prevents the homopolymerization of (<b>1</b>) even at elevated temperatures. Isolation and characterization of poly(<b>1</b>) by NMR analysis and MALDI-TOF confirms the generation of a well-defined polyallene that exhibits good thermal stability (<i>T</i>_D ca. 400 ºC) and fluorescent properties. Ring-opening metathesis polymerization (ROMP) of a high strained norbornene derivative (NBE-ⁱPr) at 80 ºC using the ruthenium vinylidene generated from (<b>1</b>) is also investigated. The discovery of ROAlMP allows for the simple accesses of well-defined polyallenes from commercially available catalysts and will ultimately guide structure-property determinations of polyallenes.

Selective Ring Opening Allene Metathesis: Polymerization or Ruthenium Vinylidene Formation

Selective ring-opening allene metathesis polymerization (ROAlMP) and ruthenium vinylidene formation from 1,2-cyclononadiene (<b>1</b>) by simple catalyst selection are discussed. Grubbs second generation catalyst (G2) favors the formation of an alkylidene leading to the ROAlMP of (<b>1</b>). Grubbs first generation catalyst (G1) favors vinylidene formation and prevents the homopolymerization of (<b>1</b>) even at elevated temperatures. Isolation and characterization of poly(<b>1</b>) by NMR analysis and MALDI-TOF confirms the generation of a well-defined polyallene that exhibits good thermal stability (<i>T</i>_D ca. 400 ºC) and fluorescent properties. Ring-opening metathesis polymerization (ROMP) of a high strained norbornene derivative (NBE-ⁱPr) at 80 ºC using the ruthenium vinylidene generated from (<b>1</b>) is also investigated. The discovery of ROAlMP allows for the simple accesses of well-defined polyallenes from commercially available catalysts and will ultimately guide structure-property determinations of polyallenes.

Cu-Catalyzed cis-selective ring-opening cross-coupling of an oxabicyclic olefin with an organoboron reagent

Cu(i)-Catalyzed cis-selective ring-opening of an oxabicyclic olefin with an organoboron reagent is described. DFT studies revealed an alternative boronic ester assisted non-canonical β-oxygen elimination as the rate-determining step.