Schmidt rearrangement photo

S0 -> Sx -> Tx transition Tt is a base of pyridine strength (pK 5), while S0 and Sj are practically non-basic (pK 0),1S9). Moreover, the site of protonation is Nl/2a for S0 andSi,butN5 forTj (Fig. 4). Hence, Hemmerich and Schmidt proposed87) that a regiospecific rearrangement of hydrogen bridges between flavin and an apoprotein environment may occur in a photo-excited flavoprotein, which would induce a unidirectional proton transfer. 

Chiral crystals generated from non-chiral molecules have served as reactants for the performance of so-called absolute asymmetric synthesis. The chiral environments of such crystals exert asymmetric induction in photochemical, thermal and heterogeneous reactions [41]. Early reports on successful absolute asymmetric synthesis include the y-ray-induced isotactic polymerization of frans-frans-l,3-pentadiene in an all-frans perhydropheny-lene crystal by Farina et al. [42] and the gas-solid asymmetric bromination ofpjp -chmethyl chalcone, yielding the chiral dibromo compound, by Penzien and Schmidt [43]. These studies were followed by the 2n + 2n photodimerization reactions of non-chiral dienes, resulting in the formation of chiral cyclobutanes [44-48]. In recent years more than a dozen such syntheses have been reported. They include unimolecular di- r-methane rearrangements and the Nourish Type II photoreactions [49] of an achiral oxo- [50] and athio-amide [51] into optically active /Mactams, photo-isomerization of alkyl-cobalt complexes [52], asymmetric synthesis of two-component molecular crystals composed from achiral molecules [53] and, more recently, the conversion of non-chiral aldehydes into homochiral alcohols [54,55]. 

The total synthesis of (+)-sparteine (85) was achieved from 2,5-norbomadione 84 in 15 steps. The key steps in the synthesis were the two ring expansion reactions, one involving an intramolecular Schmidt reaction and the other a variant of the photo-Beckmann rearrangement ring-... 

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