Yang photocyclization reaction study

Leibovitch M, Olovsson G, Scheffer JR, Trotter J (1998) An investigation of the Yang photocyclization reaction in the solid state asymmetric induction studies and crystal strac-ture-reactivity relationship. J Am Chem Soc 120 12755-12769... 

Our studies on the adamantyl (10) and decalyl (1) systems are onlytwo of several examples of the successful application of the ionic chiral auxiliary approach to asymmetric induction in the Yang photocyclization reaction. Space does not permit a full exposition of our results in this area. The interested reader may wish to consult references 17, 25, 27, 31, 35, 38 and 44 for additional examples and further details. As a note of interest, reference 44 describes the use of anionic chiral auxiliaries in the Yang photocyclization of a cationic counterion in the crystalline state aU of our other studies have been of the reverse type. 

Herrera et al. [97,98] have reported the usage of Norrish-Yang photocyclization for the synthesis of new spirocyclic monosaccharide derivatives of types 243 and 244 via a hydrogen atom transfer (HAT) reaction promoted by a 1,2-diketone 241, in its excited state, followed by C-C tetrasubstituted bond formation in a diastereo-selective manner (Fig. 8.59). Of special interest is the study of the tendency to inversion at C5 (for examples of epimerization of anomeric and pseudoanomeric radicals, see [99, 100]), probably triggered by conformational changes that the 1,4-diradical intermediate 242 undergoes in its triplet state, within its lifetime (for discussions of the lifetime of diradicals in solution, see [101, 102]) before the intersystem crossing (ISC) occurs. 

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