J. Org. Chem., Vol. 40,No. 25, 1975 3675
Photoproducts of A-Homocholestan-3-one Anal. Calcd for C20H23N302: C, 71.24; H, 6.87; N, 12.46. Found: C, 71.33; H, 6.86; N, 12.60. Hydrogenation of 21 in 95% ethanol with 5% Pdhharcoal as catalyst yielded, after evaporation of solvent, a solid, mp 164-166', whose mass spectmm has molecular ion peak m / e 339.1946 (calcd for 23,339.1946) with abundant fragments a t 242. Infrared shows no peak from 3600 to 3100 cm-I (no N-H stretch), and NMR shows no peak from 6 4.5 to 7.5 (no vinylic protons). 4-Phenyl-1,2,4-triazoline-3,5-dione with Diene la. T o 74 mg (0.50 mmol) of diene l a in 5 ml of acetone, a t Oo, was added dropwise a solution of 88 mg (0.5 mmol) of the dienophile in 2 ml of acetone. The red color disappeared instantly. The diene peak a t 262 nm disappeared on the uv, and TLC (85:15 ether-benzene, with a drop of triethylamine) showed only one spot, Rf 72. Evaporation of solvent and recryatallization from ether-pentane yielded one product in quantitative yield, mp 143-145O, identified as the DielsAlder adduct, 2 0 ir (KBr) u 1750 (s), 1700 (s), 1440 (m), 1390 (s), 765 (s), 750 (m), '725 (m), and 690 cm-' (m); NMR (acetone-de) 6 1.90 and 1.85 (2 s, 3 H, CH3-1, two kinds), 4.55 and 4.62 (2 m, 1 H), 6.1-6.8 (six lines, 2 H), 7.40 (s, 5 H); mass spectrum M+ 323.1633 (calcd, 323.1636) exhibiting retro-Diels-Alder reaction at m / e 241 (- cyclohexene). Anal. Calcd for C19H21N302: C, 70.62; H, 6.55; N, 13.00. Found: C, 70.30; H , 6.51; N, 12.72.
Acknowledgment. We thank Professor Robert B. Fairweather for stimulating discussions concerning this project and help in spectra interpretations. Registry No.--la, 54306-51-3; l b , 54306-52-4; 3a, 21102-88-5; 3b, 22738-31-4; 4, 56770-99-1; 5b, 56763-83-8; 6a, 56771-00-7; 6b, 56763-86-1; 7a isomer A, 56771-01-8; 7a isomer B, 56771-02-9; 7b isomer A, 56771-03-0; 7b isomer B, 56771-04-1; 8, 56771-05-2; 11, 707-11-9; 12,56771-06-3; 13,2809-64-5; 14 isomer A, 56771-07-4; 14 isomer B, 56816-07-0; 15, 56771-15-4; 16 isomer A, 56771-08-5; 16 isomer B, 56771-09-6; 17, 56771-10-9; 18,4242-05-1; 19,4233-33-4; 20,56771-11-0; 21,56771-12-1; 22,56771-13-2; 23,56771-14-3.
References and Notes W. A. Benjamin, Menlo Park, Calif., 1972, Chapter 8. (2) F. D. Gunstone and R. M. Heggie, J. Chem. Soc., 1437 (1952). (3) M. Yanagita and R. Futaki, J. Org. Chem., 21, 949 (1956). (4) E. J. Corey and A. G. Hortmann. J. Am. Chem. SOC.,87,5736 (1965). (5) G. Stork, A. Brirzolara, H. Landesman, J. Szmuszkobicz, and R. Terrel, J. Am. Chem. Soc., 85, 205 (1963). (6) E. C. Dufeu, F. T. Quillin, and R. Robinson, J. Chem. Soc., 53 (1937). (7) W. S. Johnson and K. E. Williamson, J. Am. Chem. SOC., 83, 4623
(1)
H. 0. House, "Modern Synthetic Reactions",
11961i (8)
keceit reports describe other bromination of kinetically produced trimethyl silyl enol ethers. See P. L. Stotter and K. A. Hill, J. Org. Chem., 38, 2576 (1973).
(a) Photooxygenations are reviewed in C. S.Foot, Acc. Chem. Res., 1, 104 (1968); (b) K. Gollnick, Adv. Photochem., 6, 1 (1968); (c) D. R. Kearns, Chern. Rev., 71, 395 (1971). (10) W. F. Johns, J. Org. Chem., 36, 2391 (1971). (11) G. I. Poos. G. E. Arth, R. E. Beyler, and L. H. Sarett, J. Am. Chem. Soc., (9)
75, 422 (1953).
(16) (17) (18) (19) (20) (21) (22) (23) (24) (25)
(a) D. Burns, D. R . Kirk, and C. Petrow, Proc. Chem. Soc., London, 14 (1960); (b) P. J. Kropp, J. Org. Chem., 29, 3110 (1964). R. B. Woodward and T. Singh, J. Am. Chern. Soc., 72, 494 (1950). L. Fieser and M. Fieser, "Reagents for Organic Synthesis", Wlley, New York, N.Y., 1967, p 238. (a) H.Stockrnann, J. Org. Chem., 26, 2025 (1961); (b) 0. Diels and K. Alder. Justus Liebios Ann. Chem.. 460. 98 (1928). G. Stork, P. RosG, N. Boldman, R. V. Coombs, and J. Tsuji, J. Am. Chem. Soc.. 87, 275 (1965). R. P. Holysz, J. Am. Chem. SOC.,75,4432 (1953). H.0. House, L. J. Czuba, M. Call, and H. D. Olmstead, J. Org. Chem., 34, 2324 (1969). A. I. Vogel, "A Textbook of Practical Organic Chemistry", 3rd ed, Lodgmans, London, 1964. E. Von Rudolff, Can. J. Chem., 39, 1860 (1961). M. C. Barrett and G. Buchi, J. Am. Chem. Soc.,89, 5665 (1967). J. A. Spencer, K. K. Schmiegel, and W. W. Schmiegel, J. Org. Chem., 30, 1626 (1965). W. Fenical, D. R. Kearns, and P. Radlich, J. Am. Chern. SOC.,91, 7771 (1969). (a) D. Burns, D. R. Kirk, and C. Petrow, Pfoc. Chem. Soc., London, 14 (1960); (b) P. J. Kropp, J. Org. Chem., 29, 3110 (1964). (a) R. C. Cookson, S. M. Ailani, and D. R. Stebens, Tetrahedfon Let., 615 (1962); (b) Org. Synth., 51, 121 (1971).
A Synthesis and X-Ray Structure Determination of the Photoproducts of A-Homocholestan-3-one T. Akiyama,'" D. Pedder,lb and J. V. Silverton Laboratory of Chemistry, N H L I , National Institutes of Health, Bethesda, Maryland 20014
Jeffrey I. SeemanlCand Herman Ziffer* L,aboratory of Chemical Physics, NIAMDD, National Institutes of Health, Bethesda, Maryland 20014 Received March 10.1975 The stereochemistry assigned to the major (3) and minor (2) photoproducts of A-homocholest-4a(5)-en-3-one has been reinvestigated. The synthesis of 5P-ethyl-A-norcholestan-3-one is described; the compound is shown to be identical with the dihydro derivative of the major photoproduct. The synthesis of 5/3-methyl-A-norcholestan%one is also described. The minor photoproduct, CzsHa6O, 5a-vinyl A-norcholestan-3-one, crystallizes in space group P21 with cell dimensions a = 10.429 ( l ) , b = 7.369 (l), c = 15.605 (2) A, P = 94.28 (2)O, and Z = 2. The structure was solved via the calculation of structure invariants and has been refined to a conventional R factor of 0.036. 'The relation of the absolute stereochemistry and the sign of the CD curves of the major and minor photoproducts and their dihydro derivatives are discussed.
The photochemistry of A-homocholest-4a(5)-en-3-one (1) and its photoproducts 2 and 3 have proven to be a rich source of mechanistic photochemical information.2 The specificities of the observed oxadi-n-methane rearrangements and photoisomerizations of the P,y-unsaturated ketones are summarized in Scheme I and are important in understanding the stereochemical consequences of these photoisomerizations. An essential aspect of these mechanistic evaluations centers on the stereochemical assignment
of the major (3) and minor (2) photoproducts from the direct irradiation of 1. A previous study of this system by Fisher and Zeeh3 in 1969 led them to a set of structural assignments based on interpretations of the NMR and CD spectra of the photoproducts. In order to determine the stereochemistry of these compounds unequivocally, parallel studies of the synthesis of 5a and an X-ray crystallographic structure determination of the minor photoproduct (2) were undertaken.
3676 J. Org. Chem., Vol. 40, No. 25,1975
Akiyama, Pedder, Silverton, Seeman, and Ziffer
Scheme I
0"
Table 1 CD Data in Methanol
& 1%
CD
4
\ -O&
6
/
8
J
I
9
/
2
-53400 +10000 -4200
3
Scheme I1
7
e
4 5a
1
0"
Cornpd
IO
5 Synthesis. The syntheses of S@-ethyl-A-norcholest-3one (sa) and 5@-methyl-A-norcholestan-3-one (5b) followed the same general procedure and are shown in Scheme 11. The key feature of these syntheses is the stereoselective introduction of the @-alkylsubstituent a t C-5 by the addition of a lithium dialkylcopper reagent to A4-cholesten-3-one (6). While the factors which govern the stereochemistry of this addition are not completely understood, Ireland et ala4have shown that the addition of lithium dimethylcopper to 6 results in the formation of only the 50methyl derivative 8b. That lithium diethylcopper introduces a 5P-ethyl group was proven by comparison of the CD curves of 8a and 8b (Table I) formed by quenching intermediates 7a and 7b, respectively, with water. Alternatively, treating 7a,b with diethyl phosphochloridate followed by reduction of the intermediate phosphonate gave 9a,b with the established 5@-alkylconfiguration. Subsequent steps in the syntheses (ozonolysis, esterification, Dieckmann condensation, hydrolysis, and decarboxylation) do not affect the configuration a t C-5. A comparison of
+2620
CD (A)
(300) (300) (295) (305)
camp
e
5b
+3960
8a
8b
-950
-1078
I _
(A) (300) (290) (240)
spectral characteristics and physical properties of 8a and the dihydro derivative of 3 showed them to be identical and quite different from the dihydro derivative of 2. These assignments contradict those made previously by Fisher and Zeeh.3 X-Ray Structure of the Minor Photoproduct. The bond lengths, valence angles, and torsion angles for the minor photoproduct are shown in Figures 1-3. Esd's for heavier atom bond lengths are
