PHOTOCOUPLING BETWEEN HALOHETEROCYCLIC DERIVATIVES AND ARYLALKENES AND ARYLALKYNES - INSTRUMENTS TO PREDICT REACTIVITY

Parameters useful to predict reactivity and regiochemical control of p hotocoupling reactions between haloheterocyclic derivatives and arylal kenes or arylalkynes have been studied. Electrochemical properties of arylalkenes and arylalkynes are shown to be useful to predict the reac tivity of the substrates. However, oxidation potentials fail as reacti vity indices if very fast photochemical processes are in competition w ith the observed complex formation between substrates and halogen atom s. The regiochemical behavior of the reaction can be estimated on the basis of dipoles of the reagents. In this case the assumptions that a reagent approaches the other on parallel planes and that the prevalent interaction is between the SOMO of the radical and the LUMO of the ot her reagent have been accepted.