A Laser Flash Photolysis Study on 2-Azido-N,N-diethylbenzylamine − The Reactivity of Iminoquinone Methides in Solution

Abstract

Photolysis of 2‐azido‐N,N‐diethylbenzylamine (1) in acetonitrile solution in the presence of various quenchers yields products of common nitrene chemistry (that is, derived from a didehydroazepine or a triplet nitrene), together with products arising from trapping of stereoisomeric iminoquinone methides. These intermediates are formed in a monophotonic process, by dediazotation of the precursor combined with a 1,4‐hydrogen shift. The reactivity of the iminoquinone methides (IQM) towards a variety of quenchers, including dienophiles and various nucleophiles, has been explored, using acetonitrile, DMF, and n‐hexane as solvents. IQM reacts efficiently with electron deficient dienophiles [kq(maleic anhydride) = 2.4·107 M−1 s−1], but not with simple olefins such as cyclohexene. IQM shows low to medium reactivity towards simple primary or secondary amines [kq(n‐propylamine) = 6.4·104 M−1 s−1], medium reactivity with sterically unhindered simple alcohols [kq(methanol) = 4.6·106 M−1 s−1], and high to very high reactivity towards thiols [kq(n‐dodecanethiol) = 1.1·109 M−1 s−1], diols, and triols [kq(glycerol) = 1.5·108 M−1 s−1], and sugars [kq(D‐glucose) = 1.0·109 M−1 s−1]. IQM also reacts rapidly with cytosine: kq(cytosine) = 3.4·108 M−1 s−1, while the reaction with adenine or thymine is less efficient [kq(adenine) = 6.4·107 M−1 s−1, kq(thymine) = 7.7·106 M−1 s−1].

Fragmentation of a dioxolanyl radical via nonstatistical reaction dynamics: characterization of the vinyloxy radical by ns time-resolved laser flash photolysis

“…The LFP set-up used in these experiments has previously been described. 17 Solutions of 7 and 8 in benzene (0.1 mM) were purged with 1 atm. of Ar, and photolyzed (l exc = 355 nm, 10 ns, 70 mJ pulse À1 ) using a flow cell to avoid precursor depletion and product build-up.…”

“…7, upper trace) is real or not is uncertain, as this growth lifetime is very close to the rise time of our LFP detector. 17 Considering the three different transient species observed, the assignment of A to thiyl radical 5 is straightforward based on a comparison with literature data, 16 as well as a comparison with a calculated spectrum of the complex 5Ábenzene. The identity of transients B (l max = 315 nm, t = 170 ns) and C (l max = 500 nm, t = 34 ns), however, still needs to be discussed.…”

Hetero‐Wolff Rearrangement of an α‐Sulfinyl Carbene: Thermally Activated Intersystem Crossing of the Lowest Excited Triplet State of a Ground‐State Singlet Carbene

“…Laser Flash Photolysis: The LFP set‐up used in Bochum has been described elsewhere 29. Solutions of 1b in acetonitrile were adjusted to an optical density of 0.3 at the excitation wavelength of λ exc = 266 nm, which corresponds to the fourth harmonic of a Spectra Physics Lab 130 Nd–YAG laser (pulse energy 50 mJ per pulse, pulse duration 8 ns).…”

Ist das [9]Annulenkation ein Möbius‐Annulen?

“…Um die Rechnungen mit experimentellen Untersuchungen zu vergleichen und um endgültig die Frage zu klären, ob das [9]Annulenkation 3 eine Möbius‐ oder eine Hückel‐Struktur aufweist, führten wir LFP‐Experimente durch. Der Aufbau der LFP wurde im Detail an anderer Stelle beschrieben 17…”

“…Die Mischung des syn ‐ und anti ‐Isomers wurden zuerst destillativ und anschließend durch Chromatographie (Kieselgel, Pentan) getrennt. Das LFP‐Experiment wurde wie zuvor beschrieben durchgeführt 17. Acetonitril wurde in spektroskopischer Reinheit für alle Experimente eingesetzt.…”