M chloroperbenzoic acid

m-Chloroperbenzoic acid was purchased from Sigma-Aldrich (Poznań, Poland). Racemic and optically active γ,δ-unsaturated esters (2a-c and 8a-c) were synthesized from the corresponding cis- and trans-piperitols as described earlier [13 ].

All manipulations involving air- and moisture-sensitive compounds were carried out in oven-dried glassware using dry solvents and standard Schlenk and vacuum-line techniques under an argon atmosphere. The 5-acetoxy-1-cyclooctene (COAc) monomer was synthesized according to the procedure described in [26 (link)]. Norbornene and cis, cis-1,5-cyclooctadiene (Sigma-Aldrich, St. Louis, MO, USA) were dried over sodium and stored under argon. Norbornene was used as a 4.6 M solution in dry chloroform. Grubbs’ catalysts of the 1st (Cl₂(PCy₃)₂Ru=CHPh, G1) and 2nd (Cl₂(PCy₃)ImesRu=CHPh, G2) generations (Sigma-Aldrich, St. Louis, MO, USA) were used without purification in the form of 0.002–0.022 M solutions in dry chloroform. m-Chloroperbenzoic acid, p-toluenesulfonyl hydrazide, and inhibitor of oxidation 2,2′-methylene-bis (6-tert-butyl-4-methylphenol) (Sigma-Aldrich, St. Louis, MO, USA) were used as supplied. Other reagents and solvents were purified using common procedures.

All solvents and reagents were
obtained from commercial sources and used without further purification.
UV–vis absorption spectra were registered at room temperature
on a V-560 JASCO spectrophotometer using calibrated 2 mL quartz cuvettes.
LC–MS analyses were performed on an HPLC instrument Agilent
1100 Series MSD equipped with a UV–vis detector and an electrospray
ionization source in positive ion mode (ESI⁺). Detection
wavelength was set at 254 nm. The spray voltage was set at 3.5 kV.
Nitrogen was employed as both drying and nebulizer gas. Mass spectra
were registered with the cone and fragmentator voltage set at 4 kV
and 80 V, respectively. An octyl column (15 cm × 4.6 mm, 3 μm
particle size) was used. An acetonitrile/water gradient was used as
follows: 0–50 min, 50–70% acetonitrile and 50–60
min, 70% acetonitrile. The flow rate was set at of 0.7 mL/min.
2,2-Diphenyl-1-picrylhydrazyl (DPPH) or 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl
(TEMPO), 2,3-dichloro-5,6-dicyanobenzoquinone, sodium persulfate, m-chloroperbenzoic acid, iron(II) chloride, and chloranil
were purchased from Sigma-Aldrich. 3-Phenyl-1,4-benzothiazine (1) and 3,3′-diphenyl-2,2′-bi(1,4-benzothiazine)
(2) were prepared as previously described.^{10 (link)}