| Abstract: | Stereoselective syntheses of 2exo, 3exo-bis (chloromethyl)-5-(Z)-chloromethylidene]- ( 9 ), 2exo, 3exo-bis (chloromethyl)5-(E)-chloromethylidene]- ( 10 ) and 2exo, 3exo-bis(chloromethyl)-5-(E)-methoxymethylidene]-6-niethylidene-7-oxa-bicyclo2.2.1]heptane ( 13 ) are presented. Double elimination of HCI from 9, 10 and 13 yielded 2-(Z)-chloromethylidene]- ( 14 ), 2-(E)chloromethylidene]- ( 15 ) and 2-(E)-methoxymethylidene]-3,5,6-mmethylidene-7-oxabicycio2.2.1]heptane ( 18 ), respectively, without loss of the olefin configuration. Ethylene tetracarbonitrile (TCE) and N-phenyltriazolinedione (NPTAD) added to these new exocyclic dienes and tetraenes preferentially onto their exo-face. The same face selectivity was observed for the cycloadditions of TCE to the (Z)- and (E)-chlorodienes 9 and 10 , thus realizing a case where the kinetic stereoselectivity of the additions is proven not to be governed by the stability of the adducts. The exo-face selectivity of the Diels-Alder additions of dienes grafted onto 7-oxabicyclo 2,2.1]heptanes contrasts with the endo-face selectivity reported for a large number of cycloadditions of dienes grafted onto bicyclo2.2.1]heptane skeletons. |
