Norrish-Yang Type

The photochemical reaction that has been most thoroughly investigated from the ionic chiral auxiliary point of view is the well-known Norrish/Yang type II reaction. One example, taken from the work of Patrick, Scheffer, and Scott [36], deals with derivatives of 7-methyl-7-benzoylnorbornane-p-car-boxylic acid (37a, Scheme 8). This compound was treated with a variety of optically pure amines to afford the corresponding 1 1 salts (37b), and in an... 

Chirally modified zeolite Norrish/Yang Type II Reaction Direct excitation Enantiodifferentiation 49-53... 

Pioneering work on the photochemical diastereocontrol in zeolite supercages was reported by Turro and coworkers in 1991 [48]. They investigated the diastereoselective photodecarbonylation of 2,4-diphenyl-3-pentanone (DPP) adsorbed in various cation-exchanged X and Y zeolites to find that the diastereo-selectivity of d9l- over mestf-2,3-diphenylbutane increases in the order LiX NaX < LiY NaY < KY. In 1996, Ramamurthy and coworkers reported the first example of photochemical asymmetric induction in chirally modified zeolites [49], where they employed the Norrish/Yang type II reaction of cis-4-tert-butyl-cyclohexyl aryl ketones to the corresponding cyclobutanols. Since then, a variety of asymmetric photoreactions in zeolite supercages have been reported as reviewed below. 

A. Enantiodifferentiating Norrish/Yang Type II Reactions in Chirally Modified Zeolites... 

For four of the reactions shown in Table 4 (entries 1,5,11, and 12), absolute configuration correlations were established between the reactant and its solid-state photoproduct. Such correlations represent one of the most powerful methods available to the organic chemist for elucidating reaction mechanisms. In the Norrish/Yang type II reaction (entries 1 and 5), for example, it allows an unequivocal determination of which y-hydrogen is abstracted, and for the di-7r-methane rearrangement of dibenzobarrelene derivatives (entries 11 and 12), it tells us precisely which atoms are involved in the formation of the initial cyclopropyldi-carbinyl diradical. 

Norrish/Yang type II CCH-4 Cr, CrSmB product study [369]... 

Fi9C9 C oH21 0 1 F15C7 CjH 7 Norrish/Yang type II FIOHIO Smj, Smi, I product study HNMR DSC OM [376] [360] ... 

Crystal Stmcture-Solid-State Reactivity Relationships Toward a Greater Understanding of Norrish/Yang Type II Photochemistry... 

For a general review on the Norrish/Yang type II reaction, see Wagner, P. and Park, B.-S., Photo-induced hydrogen atom abstraction by carbonyl compounds, in Organic Photochemistry, Vol. 11, Padwa, A., Ed., Marcel Dekker, New York, 1991, chap. 4. 

J., RandaU, L. H., Scheffer, J. R., Rettig, S. J., Trotter, J., and Wu, C.-H., Geometric requirements for hydrogen abstractabdity and 1,4-biradical reactivity in the Norrish/Yang type 11 reaction studies based on the soHd state photochemistry and x-ray crystallography of medium-sized ring and macrocycHc diketones, /. Am. Chem. Soc., 118, 6167, 1996. 

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