Beitrag zum Reaktionsmechanismus der Synthese von Seychellen [1]

New Mechanistical Details Concerning the Synthesis of Seychellen [1] In the last step of our synthesis of Seychellen ( 2 ) [1], the solvolysis of 1 , only one side‐product was formed, namely 3 (Scheme 1) . Now the structure of 3 has been elucidated, mainly by spectroscopic studies of its derivatives 7 and 9 (Scheme 2) . In order to differentiate between two different solvolytic pathways from 1 to 3 (see Scheme 1 and 3 ) d 3 ‐ 1 was prepared. Solvolysis of d 3 ‐ 1 proved the mechanism shown in Scheme 1 . Solvolysis of 1 and of 2‐epi‐ 1 , respectively, furnished the same product distribution, which makes a common intermediate a very probable. In both cases 10 is an intermediate, which is slowly converted into 2 and 3 . 2‐epi‐ 1 was prepared from 1 (Scheme 5) . Kinetic measurements with 1 , d 3 ‐ 1 and 2‐epi‐ 1 are also in agreement with the mechanism drawn in Scheme 4 : k 1 (72°) = (5,2±0,5) · 10 −5 sec −1 , k 1 (H)/ k 1 (D)(72°) = 1,4±0,15; k 2 (H)/ k 4 (H) = 0,66 and k 2 (H)/ k 2 (D) = 2,2 if k 4 (H) ≈ k 4 (D) is assumed.