General Remarks

In general, photocatalytic oxygenation reactions of tertiary amines, hydroxylation, and C=C double bond cleavage were performed under O2−balloon (Dräger, 2.0L 2165694; Cawila Football bladder 1.6 L). However, several reactions including the C=C bond cleavage and hydroxylation were carried out under sunlight. (Aza)-Diels-Alder reactions were performed under air. If not otherwise noted, yields refer to the isolated compounds, estimated to be >95% pure as determined by ¹H-NMR.

Vacuum

The following pressure was measured on the used vacuum pump and was not corrected: oil pump vacuum (OPV): 0.1 mbar.

Chromatography

Analytical thin layer chromatography (TLC) was performed on 0.25 mm silica gel 60F-plates (MACHEREY-NAGEL) with 254 nm fluorescent indicator from MERCK. Plates were visualized under UV-light or developed by the treatment with a KMnO4 solution followed by careful applying a heat gun. Chromatographic purification of products was accomplished by flash column chromatography on MERCK silica gel, grade 60 (0.040–0.063 mm and 0.063–0.200 mm)

Gas Chromatography

To monitor the progress of the reaction and to determine its yield, after stopping the reaction, the reaction flask was placed on the balance and four drops of n-dodecane (normally the weight was 20–30 mg) were added to the flask. The whole sample was then transferred into a 20-mL snap cap vial using EtOAc as solvent and the contents of the flask were washed for three times. The resulting mixture was subjected to an aqueous workup (adding 9 mL of deionized water and 8 mL of ethyl acetate) and the organic layer was transferred into a gas chromatography (GC) vial and proceeded with a GC analysis using a chromatograph 7890A GC System (Supelcowax 10 Fused

Silica Capillary Column; 30m x 0.32mm x 0.25 μm). The reaction yield was determined using the added n-dodecane as the internal standard based on a GC calibration curve.

Please note that GC analysis was performed using N2 as carrier gas with the following parameters: 50 °C at 1 min, then heating to 250 °C at a rate of 10 °C/min, and holding 1 min at 250 °C.

The typical order of elution was as follows: n-dodecane, starting material (if any was left), and the product. The mentioned elution order has been proven using authentic samples of each substance by myself.^[122]

Gel Permeation Chromatography (GPC)

GPC purifications were performed on a JAI system (JAI-LC-9260 II NEXT) equipped with two sequential columns (JAIGEL-2HR, gradient rate: 5.000; JAIGEL-2.5HR, gradient rate: 20.000; internal diameter = 20 mm; length = 600 mm; flush rate = 10.0 mL/min and chloroform (HPLC-quality with 0.6% ethanol as stabilizer) was used as the eluent.

Gas Chromatography–Mass Spectrometry (GC-MS)

To monitor the progress of the reaction (in projects of oxygenation of tertiary amines, hydroxylation, and oxidative C=C bond cleavage), 0.05 mL of reaction mixture was collected from the reaction flask using a syringe, which had been purged three times with the reaction gas atmosphere through the septum, and transfer it to a 20-mL snap cap vial. In the case of reactions performed using atmospheric air (cycloadditions), the reaction mixture sample was collected using a Pasteur pipette.

EtOAc (8 mL) and water (9 mL) were then added into the collected reaction mixture.

Then transfer the organic phase into a GC vial after filtering and proceed with performing gas chromatography–mass spectrometry (GC-MS) analysis using a Thermo Finnigan spectrometers TRACE and DSQ together. Upon this method, the reaction process can be monitored or confirm whether the products were formed.

The general parameters: Use He as the carrier gas, 50 °C for 1 min, then heating to 300 °C at a rate of 15 °C/min, and holding 1 minute at 300 °C. If solvents with a high boiling point are present in the sample after workup (e.g. DMSO, DMA, or DMF) set the solvent delay to 4 min. On the other hand, if only solvents with a low boiling points, set the solvent delay 2 min.^[120]

Mass Spectrometry

Electron ionization (EI) and EI high resolution mass spectra (HR-MS) were measured on a time-of-flight mass spectrometer AccuTOF from JOEL. Electrospray ionization (ESI) mass spectra were recorded on an ion-trap mass spectrometer LCQ from FINNIGAN, a quadrupole of-flight maXis from BRUKER DALTONIC or on a time-of-flight mass spectrometer microTOF from BRUKER DALTONIC. ESI-HRMS spectra were recorded on a BRUKER Apex IV, fourier transform ion cyclotron resonance (FTICR) mass spectrometer. The ratios of mass to charge (m/z) are indicated and intensities relative to the base peak (I = 100) are written in parentheses.

Nuclear Magnetic Resonance Spectroscopy (NMR)

Nuclear magnetic resonance (NMR) spectra were recorded on VARIAN Inova 500, 600, VARIAN Mercury 300, VX 300, VARIAN Avance 300, VARIAN VNMRS 300 and BRUKER Avance III 300, 400 and HD 500 spectrometers. All chemical shifts are given as δ-values in ppm relative to the residual proton peak of the deuterated solvent or its carbon atom, respectively. ¹H and ¹³C NMR spectra were referenced using the residual proton or solvent carbon peak (see table), respectively. ¹³C and ¹⁹F NMR were measured as proton-decoupled spectra.

1H-NMR ¹³C-NMR

CDCl3 7.26 77.16

[D]6-DMSO 2.50 39.52

The observed resonance-multiplicities were described by the following abbreviations: s (singlet), d (doublet), t (triplet), q (quartet), hept (heptet), m (multiplet) or analogous representations. The coupling constants J are reported in Hertz (Hz). Analysis of the recorded spectra was carried out with MestReNova 10 software.

Solvents

Solvents such as N, N-dimethylformamide (DMF), tetrahydrofuran (THF), acetonitrile (MeCN) in these projects (oxygenation of tertiary amines, hydroxylation, and oxidative C=C bond cleavage) were purchased from Acros (extra dry over molecular sieve). For taking the dry solvents used in these three projects, firstly the bottle was purged with nitrogen gas, then dry solvents were transferred with a nitrogen-flushed (3 times) syringe through a rubber septum into the reaction flask. The solvents used in cycloadditions were of analytical standard. These solvents could be added directly with a syringe under air.

Reagents

Chemicals obtained from commercial sources with purity above 95% were used without further purification. Some of the substrates in C=C double bond cleavage project were synthesized according to previously described methods.

Preparative Thin-Layer Chromatography

Preparative TLC plates (20 cm x 20 cm) with a 0.20mm silica gel 60 layer on alumina containing a fluorescent indicator F254 from Macherey Nagel by Merck were used to isolate compounds of smaller amount (<0.5 mmol). The TLC plates were analyzed by near (366 nm) and middle (254 nm) UV light. If necessary, iodine, potassium permanganate solution or phosphomolybdic acid (PMA) solution were used to stain the TLC plates.

Flash Column Chromatography

Flash column chromatography was used to purify crude products of larger amount (>0.5 mmol) using silica gel with a pore size of 60Å and a particle size of 40 - 63 µm (Merck) and the respective eluent.

5.2 Reaction Procedures of -Oxygenation of Tertiary Amines