Stereochemistry in the conversion of phenyldiazomethane into stilbenes and spirooxetanes caused by tetrahalogenated 1,4-benzoquinones. Effects of halogen substituents

Article abstract of DOI:10.1246/bcsj.63.630

Reaction of phenyldiazomethane (1) with tetrafluoro-1,4-benzoquinone (2a) gave isomeric mixtures of stilbenes (3, cis/trans=4.7) and spirooxetanes (4a, cis/trans= 1.1) via zwitterion intermediates. Similarly, tetrabromo-1,4-benzoquinone (2c) provided 3 and spirooxetane (4c); however, the cis/trans ratio of 3 dropped to 2.3 and 4c was solely the trans isomer. On the other hand, reaction with tetraiodo-1,4-benzoquinone (2d) afforded no spirooxetane and gave a further reduced isomer ratio of 3 of 1.9.