Azobenzene-tethered bis(trityl alcohol) as a photoswitchable cooperative acid catalyst for Morita-Baylis-Hillman reactions.

Incorporation of an azobenzene core into tethered bis(trityl alcohol) allows the photoswitchable arrangement of the two trityl alcohol units through photoisomerization of azobenzene. The differently arranged trityl alcohol units change their cooperative function to reflect the positional relationships, and thus, the activity as a cooperative acid can be controlled by light stimuli.