KINETIC AND THERMODYNAMIC CONTROL IN THE FORMATION OF STEREOISOMERIC 1 1 (4-PI+2-PI) THERMAL CYCLOADDUCTS OF FURANS WITH HEXACHLORONORBORNADIENES/

The thermally, relatively stable, main product of the reaction of fura n with dienophile 5a has been found to belong unambiguously to the end o-exo series of stereoisomeric adducts analogous to aldrin rotetracycl o[6.2.1.1(3.6).0(2.7)]dodeca-4,9-diene) 8. Also, the endo-endo isomeri c adduct 16 has been found to comprise a minor component of the total products, In similar reactions of 2-methyl-, 2-ethyl- and 2,5-dimethyl -furan with Sa, it is shown that the respective endo-endo adducts 21, 23 and 25 are important reaction products and that the thermally unsta ble endo-endo adduct 25 predominates (greater than or equal to 6:1) ov er its endo-exo isomer 26 in the early phases of reaction, its abundan ce falling with heating time. The reactions of especially the alkylate d furans with 5a provide useful sources of compounds ('oxaisodrins') h aving the skeletal features of isodrin orotetracyclo[6.2.1.1(3.6).0(2. 7)]dodeca-4,9-diene 1 otherwise not easily accessible.