CONFORMATION OF SOME TERPENOIDS
Sept. 20, 1963
phosphorane. Extensive chromatography gave the cis isomer, m . p . 125-127", which on vapor phase analysis exhibited one of the peaks indicated above. A n a l . Calcd. for CljH1~BrN03: C, 54.07; H , 3.33; Br, 23.99; K, 4.21. Found: C , 54.51; H, 3.09; Br, 24.3; N, 4.15. Repetition of the experiment b u t analyzing the product following the chromatography indicated: after 10 hr., a28:72 t r e n s : c i s ratio; after 20 hr., 26:74; and after 30 hr., 2.5375. (1.5 g., B. From the Tributyl Y1id.-p-Sitrobenzaldehyde (26) This ylid was prepared in methylene chloride b y treating a solution of t h e corresponding phosphonium bromide in methylene chloride with aqueous sodium carbonate, T h e phosphonium bromide was prepared in 607, yield by bromination of tributylphosphoranylideneacetophenone. Anal. Calcd for CmH33Br20P. C , 50.01; H, 6.93; Br, 33.28; P. 6.45. F o u n d : C , 49.57, H, 6 . 9 0 , Br, 32.88; P, 6.58.
[CONTRIBUTION FROM
THE
2795
0.01 mole) was added t o a solution of crude 2-bromo-2-(tributylphosphoranylidene)-acetophenoneZ6(0.01 mole) in methylene chloride (50 ml.) and let stand 18 hr. The solution was then concentrated, and chromatographed in benzene on Fisher A-540 alumina. The carbonyl-containing eluents (infrared) were combined, concentrated, and recrystallized from methanol t o give 0.85 g., m.p. 110-11l0. Two recrystallizations from methanol gave m.p. 118-120". Vapor phase chromatography under conditions shown t o separate the czs and trans isomers gave only one major peak, ; . e . , the cis isomer. A second crop was obtained, 0.53 g., m.p. 67-71". Recrystallization of this solid from methanol gave a material, m.p. 75.0-75.5. Vapor phase chromatography indicated this t o be a cis-trans mixture.
Acknowledgment.-Ke wish to thank Miss Joan E. Fedder for the large-scale preparation of many intermediates and compounds used in this study and Dr. D . E. Bissing for many helpful discussions.
DEPARTMENT O F CHEMISTRY A N D CHEMICAL ENGISEERING, STEVENS HOBOKEN, iY.J . ]
INSTITUTE O F
TECHNOLOGY,
Conformation of Some Terpenoids from Dipole Moment and Nuclear Magnetic Resonance Studies1 BY A. K. BOSE, M. S. ~MPNHAS, AND E. R. MALISOWSKI RECEIVED MARCH16. 1963 The stereochemistry of halogen-substituted cholestan-3-ones and allobetulones has been studied on the bases of dipole moments, proton magnetic resonance, and concepts of conformational analysis. The conformation of ring A is deduced t o be very nearly a chair in 2a-bromo- a n d 2a,4a-dibromocholestan-3-one, distorted chair in allobetulone and 2a-bromoallobetulone, planar in 2,2-chlorobromocholestan-3-one, and planar or boat in 26bromo- and 2a,2p-dibromoallobetulone.
From spectral and optical rotatory dispersion data it has been suggested t h a t certain substituted a-halocyclohexanones may prefer the boat to the chair conformation.* Since dipole moment measurements can yield additional information about the conformation of suitably substituted molecules, we undertook a study
of the dipole moments of cholestan-3-one (11)) allobetulone (V IT) several of their halogen derivatives, and some related compounds. Similar work has been reported r e c e n t l ~ . ~ Another physical method for getting information about the shapes of suitable molecules is proton magnetic resonance spectroscopy. In particular, the vicinal proton-proton spin-spin coupling constant has been shown to be sensitive t o changes in the dihedral angle between two carbon-hydrogen bonds5m6 This prompted us to include n.m.r. studies in our investigation. ~
Experimental
I, cholestane
11, cholestan-3-one, X = Y = A = B = H Dipole Moment.-The dielectric apparatus used in this study 111, 2a-bromocholestan-3-one, was essentially the same as that designed by Chien.' A parallelX = A = B = H , Y = Br plate dielectric cell was constructed especially to accommodate IV,2a,4a-dibromocholestan-3-one, very small samples while maintaining a high degree of precision. X = A = H , Y = B = Br The cell had a n effective capacitance of 55.85 ppf. and required V, 2~-chloro,2~-bromocholestan-3-one, less than 2 ml. of solution. For each dipole moment measureX or Y = Cl, Y or ment approximately 50 t o 100 mg. of sample was used. The X = Br,A = B = H d a t a listed in Table I were determined from dilute benzene solutions a t 25'. The method of Halverstadt and Kumler,* programmed for an I B M 1620 computer, was used to calculate the moments. Molar refractivities were calculated from atomic refractivities for the sodium D line. The experimental error was estimated to be approximately f0.(13 D. N.m.r. Spectra.-A \.arian high resolution DP-60 spectrometer was used for proton magnetic resonance studies. The spectra were measured a t 60 Mc./sec. on sample dissolved in deuterated chloroform containing a trace of tetramethylsilane as an internal standard. Calibration of the graphs was acV I , 3-desoxyallobetulone VII, complished by the usual side-band technique. VIII,
IX,
(1) Based in part on a paper presented before t h e Second International Symposium on t h e Chemistry of X a t u r a l Products, Prague, August, 1902 ( 2 ) For example. D. H . R . B a r t o n , D A. Lewis, and J . F McChie, J Chem. SOL., 2907 (19.57); C . Djerassi, "Optical R o t a t o r y Dispersion," 1fcGraw-Hill Book Co , I n c . , Kew York, N. Y . , 1960, p. 126.
(3) X. Allinger and SI. A DaRooge. Tetrahedvon Leileus, 19, 67R (1961); J . A m Chem. SOL.,84, 4501 (1902). (4) J . Lehn, J Levisalles, and G Ourisson, TelrnkeJron L e l f e r s , 19, 682 (1901). ( 5 ) M. Karplus, J . C h e m . P h y s . , 30, 11 (1959). (6) K . L. Williamson and W S. Johnson, J . A m C h e w . SOL.. 8 3 , 4623 (1961). ( 7 ) J Y Chien, J . Ckem E d u c . , 24, 494 (1947). (8) I F. Halverstadt and W. D . Kumler, J A m C h e m Soc , 64, 2988 (1942).
2796 TABLE I DIPOLEMOMENT DATA €I%
WI
VI1
Cholestane ( I ) o.ni6wm
2.2749
1,14390
00845719
2 27-16 2 2742
I.IG~ p = 1 . 1 4 4 3 0 Pzm
oioi~soo
.00428205 2 2740
1.14469
=
p
=
o mo -o.ooo =
= 2 2738 = 1.14489
ti y1
RD
1 2 4 . 7 cc.
=
method similar to that described by Brutcher and Bauerl*for substituted cyclopentanes. The coordinate axes were chosen, as shown in Fig. 1, 2, 3, 4, and 5, so that CorCS, Clo, CI1, and C13 lie in the x-y-plane which coincides with the over-all plane of the molecule Unit
118 1 cc.
0 2 2 I>.
Cholestan-3-one (11)
o
01.500673 00850087 00732450 00370442
2 3167 2 297.5 2 2945 2 2841
0 01744167 00761927 003:307iil 00371177
2 3486 2 3060 2.2970 2 2880
1 . 1 4 1 3 0 a = 2 771 1 . 1 4 3 2 5 @ = - 0 244 1 14338 Pzm = 305 1 cc. I 14417 = 3 . 0 3 D.
e1 YI
= 2 2739 = 1 1151C
R D = 130 0 cc.
2a-Bromocholestan-3-oneg (111) 1 . 1 4 0 2 6 a = 4 318 1 14323 = - 0,316 1 14417 P I E = 49ti 1 cc. 1 14436 p = 4 27 1)
2 2731 Y I = 1.1457ti Ro = 1 2 3 Y cc
Fig. 1.-Chair
Fig. 2.-Planar
1.
-
Fig. 3.-Boat
ci =
1
2a,~a-Dibromocholestan-3-one'0( I V ) 0 01329005 .00816799 00589400 00342010
2.3384 2 3152 2 3031 2 2920
1 . 1 4 0 9 1 a = 4 683 1.14208 0 = -0 351 1 11260 Pnm = 6 0 8 . 2 cc. 1 . 1 4 6 9 0 fi = 4 . 8 3 D.
e, = 2 2760 = 1 14527
YL
RD
=
133 7 cc.
2~-Chloro,2~-bromocholestar1-3-orie~~ (t.) 0 01842472 OO(i748.57 OOfi49.568 00414537
2 3495 2.3027 2 2994 2.2910
o
2.2842 2 2784 2 2779 2 2702
1 . 1 3 8 0 0 a = 4 080 1.14182 8 = -0 349 1 . 1 4 2 0 8 P z m = 501 9 cc. 1 . 1 1 3 2 5 p = 4 2 6 I).
= 2,2743 V I = 1.14442 K D = 1 3 3 . 7 cc. LI
3-Desoxyallobetulone ( V I ) oi3r,1893 000ill1;l .0047(i471 00273914
I 1-1156 1 14312 1.14338 1 14391
n
738 B = -0.215 Pzm = 1 7 7 . 4 cc. p = 1.54 D. a =
2 2741 YI = 1 . 1 4 4 4 9 R D = 129 2 cc =
2 2 2 0038.580(i 2
3140 3052 2807 2835
1 , 1 4 0 9 2 a = 2 278 1 14221 p = -0 201 1 . 1 4 2 9 ~ Psm = 3 1 2 . 6 cc. 1 14404 p = 3 00 D.
2 2751 YI = 1 4432 R D = 129 2 cc. ti
=
20-Bromoallobetulone ( V I I I )
n
01176193 00753980 .00414318 00146236
2 3102 2.2980 2 2843 2.2788
1.14117 1.14299 1 11352 1 14404
a = 3 133
fi
p
vi
-0.272 Pgm = 441 3 cc. f i = 3 8 7 D.
= 2.2732
1.144Ij2 R D = 137 Occ.
=
=
2.
Fig. 5.-Boat
TABLE I1 OBSERVED A N D CALCULATED DIPOLEMOMENTS ( DEBYEUSITS) p (calcd.)
Planar 1
Boat 1
Planar 2
3.03 4.23 4.86 3 40
3 03 3 91 5.01 4.25
3 03 2.33 3 14 3.40
3 03 3 91 1 89 4.23
3 2 3 3
3- Desoxyallobetulone 1.54 3 00 Allobetulone 3 87 2a-Br4 77 28-Br-
1 2 3 2
1 3 4 5
1 4 3 5
54 4S 39 73
1 54
3 17 3 30 4 53
1 54 3 74 2 18 4 71
2a-Br,Z@-Br- 4 .j9
3 78
5 05
4.63
4 29
3.22
Cyanolupan%one
3 18
5.54
6.70
4.34
J 24
P
(exptl.) Chair
Cholestane
0 22
Cholestan-3one la-BrPa-Br,4a-Br2 -Cl,2'-Br-
4 27 4 83 4.26
3.03
-54 54
88 93
54 81 20 12
Boat 2
03 33 80 40
B~-Bromoallobetulone( I X )
o
no959909 0071405Y .00.363.55 .001S.X58
2 2 2 2
3220 3094 3002
2835
1.14208 1 14247 1 14352 1 14459
=
6
4 877
-0.353 Pnm = ,599 3 cc. p = 4 77 I ) =
2 2744 1 14531 R D = 137 0 cc. LI =
YI
=
2 2 2 2
3279 3052 300.5 2933
1 1384.5 a = 4 009 1 . 1 4 0 5 2 0 = -0 459 1 , 1 4 1 0 4 Pzm = 5 7 3 . 2 cc. 1 14273 p = 4 5 9 D.
3 93"
Apparent conformation
Chair Predom.chair Predomchair Planar
rlistort chair 1)isturt. chair Planar o r boat Planar or boat Uistort chair
Taken from reference 4.
2a,2p-Dibrornoallobetulone( X ) 0 0134.5447 00745991 0008,5824 00480183
2
vectors locating the x,y,z-coordinates of various substituents for the various forms of ring A are listed in Table 111. Utilization of the unit vectors provides a
Compound
Xllobetulone (1.11) 0 0172GG96 01284445 00611322
Fig. 4.-Planar
