When heated in pyridine at 80°C, pentacarbonyl[(2E)-3-cyclohexenyl-3-(dimethylamino)-1-ethoxy-2-propen-1-ylidene]chromium (1-Cr) and -tungsten (1-W) complexes undergo 6π-electrocyclization and subsequent reductive elimination to yield the cyclohexane-annelated cyclopentadiene 6, which equilibrates by 1,5-hydrogen shift with its more reactive isomer 7. The latter molecule is efficiently trapped in Diels−Alder reactions with various alkynes 2 and styrenes 8 to give the cyclohexane-annelated norbornadiene 3 and norbornene derivatives respectively, with high regio-and diastereoselectivity in 15−91% yields. The enol ether moiety in compound 3 is particularly easily hydrolyzed, probably due to the through-space interaction between the two double bond moieties, so that the norbornenone derivatives 4 are isolated in all but one case after chromatographic purifica-