1124
NOTES
VOL.
22
ferred into a separatory funnel, acidified with hydrochloric study has been made of the sodium acetat,e-cat,aacid. and shaken. The slightly yellow organic phase was lyzed rates of bromination of norcamphor (I),synseparated, the aqueous solution was washed with 60 ml. of chloroform, and the chloroform was combined with the and anti-7-chloronorcamphor (I1 and 111), exocarbon tetrachloride solution. The resulting liquid was dried '3-bromonorcamphor (IV), d-camphor (V) and endoover anhydrous sodium sulfate, filtered, and evaporated to 3-bromod-camphor (VI). dryness. The residue was crystallized from petroleum ether Ketones I, 11, and 111 were prepared from the at -5" C. to give 1.273 g. of white crystals, m.p. 88-89' C. Further crystallization raised the melting point t o 90-91' C. corresponding ezo-norborneols by chromic acid oxThe melting point was undepressed upon admixture with idation, a method found to be superior to nitric libocedrol p-methoxythgmol adduct. The material was sep- acid ~ x i d a t i o n1-111 . ~ were purified by regeneration arated using the previously described procedure1 into libo- from their pure semicarbazones by steam distilla#cedrol, m.p. 86-87" C., and p-methoxythymol characterized tion from oxalic acid solution. d-Camphor (V) was as its p-nitrobenzoate, m.p. 126-127" C.; both melting points brominated under acid-catalyzed conditions5to give were undepressed on admixture with authentic samples. The filtrate was diluted t o 30 ml. with petroleum ether c1and extracted with 150 ml. of 5% sodium hydroxide in 3 portions. The petroleum ether solution was dried and evaporated to dryness. The residue was heated on a steam bath with 1.0 g. of p-nitrobenzoyl chloride in 5 ml. of pyridint., cooled, and treated with 25 ml. of 10% bicarbonate solution and 50 ml. of ethyl ether. The ethyl ether solution was washed with 50 ml. of 10% sodium carbonate and 50 ml. of 10% hydrochloric acid, dried, and evaporated t o dryness, The residue was crystallized from methanol to give 234 mg. of libocedrol p-nitrobenzoate, m.p. 165-170" C. (8%). Further crystallization from isooctane followed by crystallization from methanol raised the melting point to 174-175" C., undepressed on admixture with an authent,ic sample. The sodium hydroxide extracts were combined, acidified with hydrochloric acid, and extracted with ethyl acctat'e. VI, whose structure has been unequivocally estaL The extract was dried with anhydrous sodium sulfate, filtered, evaporated to dryness, and p-nitrobenzoylated in lished by an x-ray crystal structure deterinina~,~ (IT.')wab prepared the usual manner t o give a very small amount of material of t i ~ n .ezo-3-Bronionorcamphos indefinite melting point which waa not further invest,igated. by a similar method. In addition to the kinetic arThus, the reaction gave 1.020 g. (49%) of libocedrol and gument given belov, the exo-configuration assigned 0.425 g. (20%) of the original material. to the bromine atom of IT7 was consistent with Comparison of the infrared spectra, of the synthetic libocedrol and the naturally occurring material revealed that comparison of its ultraviolet absorption with those they were identical. Also the benaoylation of the synthetic of VI and its em-isomer (Table I). libocedroll' gave a benzoate, m.p. 137-138" C., which did not depress the melting point of the naturally occurring TABLE I libocedrol benzoate.
n
n
c L T R A V I O L E T S P E C T R a L DATA"
Acknou:ledgment. The authors are indebt,ed t o the California Cedar Products Co. for sponsoring a research grant supporting this investigation, and t o Mr. Charles P.Berolzheimer for his interest and c,ooperation. FOREST PRODUCTS LABORATORY UNIVERSITY OF CALIFORNIA I~ICNMOND, CAL.
Ketone ~~
Solvent
hmBxM
p
F
~
d-Camphor(V) ezo-3-Bromod-camphor rnd0-3-BrOmO-
&camphor( V I ) ?;orcamphor( 1: em-3-Bromonorcamphor( I V )
289.5h 2926 312'J 30Gh 307 j 287 312 317
h
32 23 80 100 (16 5 30 0 84 4 73 2
Determined with a Cary Model 11M recording trophotometer using 1-em. quartz cells. ' R. C. Coolcaon, J . Chem. Soc., 1954, 282 and references cited thcreii;. ___ ( 3 ) (a) ,J. 1). RobertP, IT-. Bennrtt. and It. Armstrong, WILLIAM 6. WOODS'AND J o m ID.ROBERTS J . . I m . Chem. Soc., 72, 3320 (1050). ( h ) J. D. 1tot)er:s and W. Bennett, b. Am. Chem. Soc., 7 6 , 4623 (1954). ( r ) IT.G Received February 66, 1967 Woods, R . A. Carboni, and J. I>. Roberts, J . . I n t . Chetii Soc., 78,5653 (1956). ( 4 ) 6 . 1). Roberts, F. 0. Johnson, and It. A. Carlioni, .i In continuation of earlier work on the effect of structure on reactivity in the norbornyl ~ y s t e ma, ~ Am. Chern. Sac.: 76, 56\12 (1954). (a5) F. 9. Kipping and W.J. Pop
