Photochemistry of Matrix Isolated (Trifluoromethyl)sulfonyl Azide, CF₃SO₂N₃

Abstract

The photochemistry of matrix isolated (trifluoromethylsulfonyl) azide, CF3SO2N3, has been studied at low temperatures. Upon ArF laser irradiation (λ = 193 nm), the azide eliminates N2 and furnishes triplet [(trifluoromethyl)sulfonyl]nitrene, CF3SO2N, which has been characterized by IR and EPR spectroscopy. Upon subsequent UV light irradiation (λ = 260-400 nm) the nitrene converts to CF3N═SO2 and CF3S(O)NO through a Curtius-type rearrangement. Further two new species CF2N═SO2F and FSNO were identified together with CF2NF, SO2, F2CO, CF3NO, and SO as side products. In addition, triplet nitrene CF3N was detected by its EPR and IR spectra. The complex stepwise photodecomposition of matrix isolated CF3SO2N3 is discussed in terms of the observed photolysis products and quantum chemical calculations.

Direct Observation of Carbamoylnitrenes

“…[14] Recently,w eh ave shown that reactive a-oxo-nitrenes can be generated efficiently through the irradiation of a-oxo-azides with an ArF laser in solidn obleg as matrices. [15] For instance, the ArF laser photolysis of the matrix-isolateda cyl azide FC(O)N 3 enabled the direct observation of the carbonyl nitrene FC(O)N, [15a] which was not observed in ap revious study of the photolysis in solid matricesb yu sing am ercuryl amp (l > 200 nm). [16] The use of the short-pulseArF laser has the distinct advantage of reducing secondary irradiation of the photolabile a-oxonitrenes by the unwanted UV or visible light from the mercury or xenon lamps.…”

Photochemical C−H Amination of Ethers and Geminal Difunctionalization Reactions in One Pot

“…An experiment in which irradiation is interrupted for defined times showed no conversion during the dark periods (see the Supporting information). To distinguish a concerted C−H insertion of triplet N ‐nonaflyl nitrene from a radical process, THF ( 2 a ) and nonaflyl azide ( 1 a ) were mixed in the presence of half or two equivalents of 2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPO, 10 ) in rigorously deoxygenated solution and irradiated with UV light at 25 °C for 7.5 and 3.5 h, respectively, until complete consumption of 1 a . With half an equivalent of 10 , a 1:2:1 mixture of 5 a / 4 a / 11 was observed in the crude reaction mixture, whereas with two equivalents of TEMPO ( 10 ), a 1:2 mixture of 4 a / 11 was formed with 52 % mass balance .…”

“…The following mechanism is the most consistent with all observations (Scheme ). Triplet nitrene 12 is initially formed by photolysis. Both the reaction with TEMPO ( 10 ) and the KIE speak against a concerted C−H insertion reaction via transition state 13 , but rather point to facile hydrogen‐atom abstraction from ethers 2 by nitrene 12 to generate α‐alkoxy radicals 15 .…”

Fast Heavy‐Atom Tunneling in Trifluoroacetyl Nitrene

“…Both signals slowly disappear while keeping the matrix in the dark, but the rate is dramatically slower than the disappearance of CF 3 C(O)N in Ar matrix (IR spectroscopy), nitrenes can still be observed after 12 h. In the more rigid Ar matrix, one strong and persistent signal occurred at around 8690 G with ZFSP of | D / hc |=1.75 cm −1 and | E / hc |=0.01 cm −1 . It corresponds to the known triplet nitrene CF 3 N (| D / hc |=1.741 cm −1 and | E / hc |=0.0 cm −1 ), which is produced through the secondary photolysis of CF 3 NCO. Two much weaker signals with x 2 and y 2 splitting at around 6250 and 8510 G (| D / hc |=1.17 cm −1 and | E / hc |=0.045 cm −1 ) vanished completely in one hour in the dark at 4.2 K (Figure S37), coinciding with the kinetics for the tunneling disappearance of CF 3 C(O)N. The observed significant variation of D values for CF 3 C(O)N in different matrices suggest the existence of interaction with surrounding molecules.…”