摘要:
Chemical Corn m u n i cations NUMBER 14/1965 21 JULY Transannular Hydride Shifts in Bicyclic Systems By R. A. APPLETON and S. H. GRAHAM (Edward Davies Laboratories, A berystwyth) EVIDENCE has been accumulating that the bicyclo- [3,3, llnonane ring system exists as a t~in-chair.l-~ Measurements by Brown, Martin, and Sim,4 which agree with those of Dobler and dun it^,^ give the separation between C-3 and C-7 as 3-06 %., with a probable separation of 1.7 between the two endo- hydrogen atoms of the C-3 and C-7 methylenes. Some strain is present in the molecule since the average bond angles at positions 2, 3, 4, 6, 7, and 8 is 114”; this strain will be relieved when C-3 becomes trigonal as in a carbonium ion, and the situation is analogous to that which exists in medium-sized rings.This suggests that transan- nular hydride shifts might be observed in the bicyclic system similar to those which have been investigated by the schools of Cope and of Prelog6 We now report the first demonstration of such a shift. 7fl-Methylbicylo [3,3, llnonenes (I) and 3- methylenebicyclo [3,3, llnonanes were converted by boiling formic acid into the same equilibrium mixture, consisting of 3-methylbicyclo [3,3,1]- nonene (11) (ca. 93%) and (I) (ca. 7%: analyses by p.m.r.’ spectra and g.1.c. over tritolyl phosphate on deactivated celite). The structure of the new hydrocarbon (11), indicated by the absorption of the mixture at 3003 and 817 cm.-1 and at r 4.62 (doublet, one olefinic proton) and 8-32 (singlet, allylic methyl group), was confirmed by hydrogena- tion of the mixture to 3a-methylbicyclo [3,3,1]- nonaneS (86.5%) and the 3P-epimer (13.5%).A sample of 3-methylenebicyclononane rearranged into the same equilibrium mixture of (I) (7.2%) and (11) (92.8%) when set aside for some months. Similar hydride transfer is involved in the rearrangement8 of l-methylcyclo-octene to 5- methylcyclo-octene (2.5%) in formic acid, and the dehydration of l-methylcyclo-octanol to l-methyl- cyclo-octene (73%) and 5-methylcyclo-octene (6.3%). Me (I 1 @> (Receioed, May 4th, 1965.) 1 M. W. J . Pumphrey and M. J. T. Robinson, I.U.P.A.C. Congress, July, 1963. * W. A. C. Brown, K. Eglinton, J. Martin, W. Parker, and G. A. Sim, Proc. Chem. Soc., 1964, 57. a M. Dobler and J. D. Dunitz, Helv. Chim. Acta, 1964, 47, 695. W. A. C. Brown, J. Martin and G. A. Sim, J. Chem. SOC., 1965, 1844. For review see J. Sicher in “Progress in Stereochemistry,” Ed. P. B. D. de la Mare and W. Klyne, Butterworths, London, 1962, Vol. 3, pp 243-246. @ R. A. Appleton and S. H. Graham, to be published. ’ For which we thank Dr. D. A. Wilson, Cardiff. S. H. Graham and C. F. Mathews, unpublished work.298 CHEMICAL COMMUNICATIONS The following paper was originally published in Chem. Comm., 1965, 197. Unfortunately, errors in the We are therefore p.eproducing the whole pafier with diagrams were such as to render the paper unintelligible. revised diagrams.
ISSN:0009-241X
DOI:10.1039/C19650000297
出版商:RSC
年代:1965
数据来源: RSC