Generation and reactions of new ether and acetal functionalized tricyclo[3.3.0.03,7]oct-1(5)-ene derivatives. DSC and NMR studies on the [2+2] retrocycloaddition of several cyclobutane dimers

Two new highly pyramidalized tricyclo[3.3.0.03,7]oct-1(5)-ene derivatives containing ether and acetal functionalities have been generated, trapped as Diels–Alder adducts and dimerized. The initially obtained diene dimers were photochemically converted into cyclobutane derivatives. The thermal reversion of several cyclobutane derivatives to the corresponding dienes has been studied by 1H NMR, ab initio calculations and DSC. For the first time, transannular additions of bromine and iodine to a diene dimer of this series have been observed.