Abstract
The photocyclisation of enantiomerically pure α-heteroatom-substituted β-methyl butyrophenones 1 results in Norrish II cleavage and in Norrish II / Yang cyclisation products, cyclobutanols 2, the latter being formed with excellent diastereoselectivities and with relative yields which were strongly depending on the Hbonding activity of the α-substituent.
Keywords: photocyclisation, norrish-yang reaction, butyrophenones, cyclobutanols