Norrish type II photoreaction

Keywords a-oxoamide, inclusion crystal, Norrish type II photoreaction, /1-lactam... 

J. Brunckova and D. Crich, Intramolecular hydrogen atom abstraction the type /1-oxygen effect in the Norrish type II photoreaction, Tetrahedron, 51 (1995) 11945-11952. 

Norrish type II photoreaction Intramolecular abstraction of a y-hydrogen by an excited carbonyl compound to produce a 1,4-hiradical as a primary photoproduct e-g ... 

J. (1994) Ionic chiral handle-induced asymmetric synthesis in a solid state norrish type II photoreaction. Tetrahedron Asym., 5, 1415-1418. 

The low quantum yield indicates that intermediate complexes and diradicals decay unproduc-tively. In general, Norrish type II photoreactions and other hydrogen abstraction processes must be overcome in order to achieve successful cycloaddition. Only in a few reported cases is intramolecular hydrogen abstraction a serious competitive reaction path. For example, the cycloheptenyl-substituted ketone 5 yields an oxetane 6 in addition to a cyclobutanol derivative 758, whereas the unsaturated cycloheptanone 8 only gives oxetane products 9 and 10 on irradiation59. The main product 10 was converted in two steps to azulene in 25 % overall yield. The reaction sequence 11 - 12 - 13 also demonstrates the high synthetic potential of the intramolecular Paterno-Biichi reaction61. 

Punctatin A (34), also known as antibiotic M 95464, is an unusual metabolite which has been isolated from the dung fungus Poronia punctata. An enantiospecific synthesis of (34) has now been described which features, amongst other things, use of the Norrish type II photoreaction viz (32)- -(33) to elaborate the cyclobutane ring... 

Norrish Type II Process, Norrish Type II Photoreaction,... 

Photochemical alkane carbonylation with RhCl(CO)(PMe3)2 is also possible. This seems to operate by initial photoextrusion of CO from the catalyst, oxidative addition of the alkane C—H bond, addition of CO to the metal, followed by insertion, and then reductive elimination as shown in Figure 3. Preferential reaction at the 1 ° or 2° C—H bond is found. Here the initial product does not seem to isomerize, but Norrish type II photoreactions tend to degrade the aldehyde product. Moving to longer wavelengths minimizes the Norrish degradation problem, but the selectivity of the catalytic system then falls off No more than 30 turnovers have been observed to date (e.g. equation 24)... 

Koshima, H., Maeda, A., Masuda, N., Matsuura, X, Hirotsu, K., Okada, K., Mizutari, H., Ito, Y., Fu, T. Y, Scheffer, J. R., and Trotter, J., Ionic chiral handle-induced asymmetric-synthesis in a solid-state Norrish type II photoreaction. Tetrahedron Asymm., 5, 1415, 1994. 

Hasegawa, T, Arata, Y., and Kageyama, A, The Norrish type II photoreaction of benzoylvalerates stereochemical control in 1,4-biradical cyclisation. Tetrahedron Lett., 24,1995, 1983. 

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