Cyclodecene complexes

The same allylic species can be formed from the related 1,3-diene and indeed cw,ci5-l,3-cyclodecadiene yields at least 38% tmns-cyclodecene although the saturation of one double bond which did not involve its neighbor should obviously yield the more stable cis isomer. The result implies that the allylic intermediate, which would be formed initially in the cis,cis conformation, has time to rearrange on the siurface to its more stable cis,trans configuration before it reacts further with hydrogen. The possibility that the ct ,cts-l,3-cyclodecadiene isomerizes first to the less stable cis,trans-diene was discounted. The rearrangement of the allylic intermediate could be accomplished via a o-bonded complex, as indicated on page 142 of Section III,C. 

The conversion of the m-monoolefin to its silver nitrate complex 1 was accomplished by adding 1.66 g. (0.010 mole) of the distilled reaction product to a solution of 1.70 g. (0.010 mole) of silver nitrate in 50 ml. of boiling methanol. The resulting solution, when cooled, deposited the complex as white needles, m.p. 79° dec. recrystallization from methanol separated 1.0 g. of the complex, m.p. 80° dec. After this complex had been partitioned between water and ether, the ether phase was separated, dried over magnesium sulfate, and concentrated. Distillation of the residual liquid in a short path still separated 0.45 g. of the pure (Note 6) cfs-cyclodecene, b.p. 70° (1.0 mm.), n B 1.4852. 

Complex mixtures were obtained and the formation of both cis and trans cyclodecenes (47 and 48) in a 3 1 ratio indicates that, contrary to the cation (vide infra, equation 71), the cyclopropylcarbinyl radical does not give a stereospecific ring expansion ... 

The trons-cycloalkenes 37a, 67, and trans-cyclononene 227 react with diironnonacarbonyl 228 to form the tetracarbonyliron(O) complexes 229-231 with the frans-cyclooctene complex 229 being significantly more stable than that of trons-cyclodecene 231 (177). The bicyclic triene 232 reacts with 228 preferentially at one of the trans double bonds of the trans, trans- cy-clodecadiene substructure. In line with the expected stability, the trans, cis-cycloocta-1,5-diene 234 and trans, ris-cycloocta-1,3-diene 236 react with 228 exclusively at the trans double bond to give the complexes 235 and 237. In the complex 238, tetracarbonyliron(O) is bonded to the bridgehead double bond of bicyclo[4.3.2]deca-7,9-diene (184b) (177). 

E -cyclooctene is subject to thermal racemization. The molecular motion allows the double bond to slip through the ring, giving the enantiomer. The larger and more flexible the ring, the easier the process. The rates of racemization have been measured for E-cyclooctene, Zf-cyclononene, and Zi-cyclodecene. For E-cyclooctene the half-life is Ih at 183.9° C. The activation energy is 35.6 kcal/mol. E-cyclononene, racemizes much more rapidly. The half-life is 4 min at 0° C, with an activation energy of about 20 kcal/mol. F-cyclodecene racemizes immediately on release from the chiral platinum complex used for its preparation. ... 

The ease of rotation will depend on the ring size. It is observed that trans-cyclooctene is quite stable to thermal racemization, and can be recovered with no loss in rotation after 7 days at 61°C. When the ring size is larger, it becomes easier for rotation of the plane of the double bond through the belt of the ring atoms to occur, and racemization takes place more readily. The half-life for racemization of trans-cyclononene is 5 min at 0°C. The resolution of /rans-cyclodecene has been accomplished using the techniques developed for irons-cyclooctene and trans-cyclononene, but it racemizes immediately on its release from the chiral platinum complex employed for its resolution. ... 

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