Oxo-Spirocyclization into Spirocyclic Quinol Variants

Ishihara and Uyanik also worked on this enantioselective oxo-spirocyclization using different and more conformationally flexible chiral X -iodane catalysts generated in situ from lactate-based iodoarenes of t)q)e 109 and m-CPBA [80]. Enantiomeric excesses up to 92% could be obtained imder Kita s conditions for the conversion of 105a into 108a using the iodoarene 109 (Fig. 26). Ishihara and 

Another different C2-symmetric iodoarene system, based on an all-carbon and quite rigid a f -dimethanoanthracene core, was recently described and tested by Ibrahim for catalytic asymmetric Kita s spirolactonization [82]. For example, the para-methylated variant of the iododimethanoanthracene 113 in a 2 1 CHCI3/ CH3NO2 solvent mixture at -20°C converted the 4-brominated variant of naphthol 105 (i.e., 105b) into the corresponding spirolactone 106b in 63% yield with 67% ee (best ee) (Fig. 28). The use of the para-methoxylated variant of 113 under the same 

28 Ibrahim s catalytic asymmetric dearomative spirolactonization of naphthols 

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