Rearrangements of pinane derivatives. Part III. Solvolysis of the 2-pinanyl p-nitrobenzoates

Abstract

Methanolysis of the 2-pinanyl p-nitrobenzoates in the presence of base gives a mixture of products including both cis-and trans-methyl 2-pinanyl ethers from both esters. In contrast, other substitution products show a rigid retention of stereochemistry. It is suggested that each ester forms a delocalised ion, and that these ions can subsequently be interconverted. The results contrast with data reported from the study of the nopinol system, but both sets of results have been shown to be consistent with a mechanism of interconversion of ions in which two possible reaction paths exist, the direction of reaction being controlled by the substituent on C-2. Elimination products fit this general pattern except for a very high yield of a-pinene from the cis-ester, which may arise from elimination within an intimate ion pair, rather than from the ' free ' ion. The trans-ester, in contrast, gives an intimate ion pair which undergoes collapse rather than elimination. 6 N. A. Abraham and M.

Biogenetic-Type Rearrangements of Terpenes

“…Both types of products are usually formed from the addition of acids to the pinenes. Methanelysis of the cis-and trans-pinyl p-nitrobenzoates (46-0PNB and 48-0PNB) gives, in part, separate sets of products, and to a substantial degree a common distribution of products (96). Although the energy barrier separating the isomeric ions here is clearly small, it is noteworthy that the bornyl and fenchyl pnitrobenzoates (41-0PNB, 3%; 43-0PNB, 34%) resulting from internal return are evidently formed stereospecifically.…”

Untitled

“…La migration du HÀC (3) ou du C(6) (responsables de la formation de la pinocamphone 3a ou du camphole  nal 2a, respectivement) est conse  cutive a Á la formation du carbocation ou concomitante avec louverture de loxirane. La migration du C (7) (conduisant au fenchole  nal 4a) est peu ou pas observe  e pour des raisons e  lectroniques dans le premier cas [14], ste  re  ochimiques dans le second [15]. Ces diffe  rentes transpositions de Wagner-Meerwein sont repre  sente  es dans le scheÂma 3.…”

“…Il sagit dun me  canisme concerte  (scheÂma 4). Louverture de la liaison C(2)ÀO est toujours assiste  e, par la migration du C(6) dans le cas ge  ne  ral, par latome de S suivie de la migration du C (7) [14], on peut imaginer que ces deux ions de stabilite  s diffe  rentes se  quilibrent. Les proportions relatives de camphole  nal 2 et de fenchole  nal 4 observe  es a Á la fin de la re  action de  pendent alors des vitesses relatives de  quilibration et de  volution des ions ponte  s. Cette compe  tition est e  videmment fonction des conditions ope  ratoires.…”

“…{{[(4R)-5,5-DimeÂthyl-4-(2-oxoeÂthyl)cyclopent-1-eÂnyl]meÂthyl}thio}aceÂtate de meÂthyle (2g): CC (e Âther de pe  trole/Et 2 O 90 : 10): en me  lange avec 4g. RMN-1 H (repe  re  par quelques signaux) 1 ): 9,77 (t, J 2, CHO); 5,6 (m, HÀC(4)); 183 (11),150 (29),139 (28),135 (13), 109 (16), 108 (13), 107 (100), 106 (41), 105 (17), 93 (24), 91 (35), 79 (23), 77 (14), 67 (10), 53 (11), 45 (13), 41 (22), 39 (11), 29 (11). SM-HR: 256,111760 (M , C 13 H 20 O 3 S ;calc.…”

Norpinyl‐Norbornyl‐Umlagerungen: Bicyclo[3.1.1]heptan‐, 4‐Methyl‐ und 6‐Methylbicyclo[3.1.1]‐heptan‐Derivate

“…Wir berichten in dieser und den folgenden Mitteilungen iiber eine systematische Untersuchung sekundarer, tertiarer und mesomeriestabilisierter 2-Bicyclo-[3.1.l]heptyl(Norpinyl)-Kationen. 10 …”