Unambiguous proof for preferred 4 + 4 cycloaddition in the dimerization of photoexcited N-methyl-2-pyridone
Abstract
Photochemical dimerization of N-methyl-2-pyridone in water gives exclusively the 4 + 4 cyclo-addition products trans–anti(3)(the known product), trans–syn(4), cis–anti(5), and cis–syn(6a) in yields of 51, 0·6, 11·2, and 6·8%, respectively; structures were assigned on the basis of spectral and chemical evidence.