Enantiomerically pure cyclopentadienes

7‐(Dimethylamino)tricyclo[5.2.2.01,6]undecene Derivatives from β‐Cyclohexenyl β‐Dimethylamino‐Substituted α,β‐Unsaturated Fischer Carbenes

“…β‐(Dimethylamino)‐substituted α,β‐unsaturated Fischer carbene complexes 1 were prepared from lithiated 1‐ethynyl‐1‐cyclohexene, the respective hexacarbonylmetal, triethyloxonium tetrafluoroborate and dimethylamine according to the previously developed one‐pot procedure in excellent yields (94% for 1 ‐Cr1 and 87% for 1 ‐W). As mentioned previously,2 the cyclohexane‐annelated cyclopentadiene 6 is formed via a 6π‐electrocyclization, and the observed regional and facial selectivities in the Diels−Alder reactions of 7 with dienophiles 2 can be explained on the basis of a model proposed by Winterfeldt3 (Scheme 2). The applied alkynes add onto the more reactive 1,3‐diene 7 with syn ‐facial selectivity (with respect to the hydrogen in 7 ) and, as far as the larger groups R L are concerned, the ortho ‐selectivity rule (with respect to the dimethylamino group in 7 ) is obeyed 2…”

Facile Synthesis of 7-Dimethylamino-endo-tricyclo[5.2.2.01,6]undec-10-en-9-ones

“…The regional and facial selectivities in the above Diels−Alder reactions of 8 can be explained on the basis of a model proposed by Winterfeldt (Scheme ) 18. The applied alkynes 3 add to the more reactive 1,3‐diene 9 with syn ‐facial selectivity (with respect to the hydrogen in 9 ) and the larger groups R L obey the ortho selectivity (with respect to the dimethylamino group in 9 ) 19.…”

Enantioselective Synthesis of Cyclopentadienes by Gold(I)‐ Catalyzed Cyclization of 1,3‐Dien‐5‐ynes

“…For instance, they are reactive diene counterparts in the Diels–Alder cycloaddition,2 one of the most useful synthetic reactions for the construction of the cyclohexane moiety, with up to four contiguous stereogenic centers being created in a single operation, usually through an endo ‐favouring transition state. In this context, enantiomerically pure cyclopentadienes3 have been applied in the kinetic resolution of racemic dienophiles and as chiral templates 4. However, these compounds are not readily available from the chiral pool and, moreover, the asymmetric synthesis of cyclopentadienes from achiral substrates is almost unknown 5…”