2086
COMMUNICATIONS TO THE EDITOR
1-01. 83
FORMATION OF EPOXIDES IN THE PYRROLE AND FURAN SERIES BY PHOTOOXIDATION
my, E 30,000) conversion to tetraphenylfuran with hydrogen iodide in glacial acetic acid, and Sir: reduction to dibenzoyldiphenylethnrlc in ethnnolic Although the oxidation of indoles by air and light sodium hydros~lfite.~ has been studied e ~ t e n s i v e l y , ~little . ~ . ~ is known The second oxidation product from I (;1O~/c) about the course of pyrrole p h o t ~ i i x i d a t i o n . ~was ~ ~ ~identified ~~~ as a-N-benzoylarnino-0'-benzoyl2,3,4,3-Tetraphenylpyrrole( I ) , for example, has stilbene (IV), m.p. 191" [-lnnZ. Calcd. for C2aHslbeen reported7 to yield only tars when irradiated NO?: C, 83.35; H , 5.25; N,3.47. Found: C, with oxygen. We now have found that under S3.18; H, 5.43; N, 3.471. IV shows infrared vqry mild conditions, i.e., exposure to air in meth- bands a t 5.95 p and 6.04 p , can be hydrolyzed to anolic solution during irradiation with a 150- dibenzoylphenylmethane, and was synthesized watt reflector flood light, in the presence of methyl- independently by benzoylation of a-amino-a'ene blue, 2,3,4,5-tetraphenylpyrrole undergoes benzoylstilbene. lo ready oxidation, yielding products in 85% yield. Photooxidation in the presence of potassium The main product (55%) is the epoxide, 5- hydroxide led to a rearrangement of the benzilic methoxy-3,4-epoxy-2,3,4,5-tetraphenyl-A1-pyrroline acid type" with formation of the lactam, V (35YG), (11), m.p. 164-1G5" [ A n d Calcd. for C29H23N02: m.p. 213-215' (XE3': 2.95 y, 3.19 p and 5.85 C, S3.43; H, 5.55: N, 3.36; OCH1, 7.43. Found: p ) identical with the product12 independently C, 63.45; H, 5.43; N , 3.15; OCH3, 7.421. I1 prepared from 2,2,3,4tetraphenylcrotonolactone shows no OH, NH or carbonyl absorption in the and ammonia. Epoxide formation also was observed in the infrared, is reduced to I with zinc in acetic acid, and is converted by 1 N HCl to cis-dibenzoylstilbene photooxidation of tetraphenylfuran. Whereas the oxide (111), m.p. 172-173" [Anal. Calcd. for (228oxidation in methanol led chiefly to ckdibenzoylH2"03: C, 83.15; H, 4.98. Found: C, 83.25; stilbene and 2,5-dimethoxy-2,3,4,5-tetraphenyl-2,3H, 5.091. Proof of structure of 111, hitherto dihydrofuran, both I11 (45%) and VI (20%), m.p. 151-152', were formed during photooxidation 0 0 in acetone. Compound VI (X:zXc13 5.75 p, 5.99 c6M, c~H~--~-\-;-c~H~ p) is identical with the enol benzoate recentIy to result from the benzoylation of dibenzoylphenylmethane. l 4 I1 111 The details of this work and discussion of the mechanisms involved will be reported separately. COVTRIBUTION No. 1602 FROM THE STERLING CHEMISTRY LABORATORY
IV
VI
T'
VI1
unreported, rests on its infrared and ultraviolet 5.93 p ; 249 absorption spectra8 (Xg?$'3 (1) P. M. R a y , A n n . Reg. Plant Physiol., 9, 81 (1958). (2) B. Witkop, et aZ., Erperientia, 8 , 36 (1952), and references cited therein. (3) Z. Yoshida and hf. Kato, THISJ O U R N A L , 76, 311 (1954), and references cited therein. (4) W. Metzger and H. Fischer, A n n . , 627, 1 (1937). ( 5 ) F. Bernheim and J. Morgan, Nature, 144, 290 (1939). (6) R. H. Linnel and S. Umar, Arch. Biochem. and Biophys., 67, 264 ~~1-0 .-5 -5 1 I
(7) J. hlartel, Com$t. r e n d . , 244, 626 (1957).
TALEUNIVERSITY HARRY H. WASSERMAN SEW HAVEN, COXN A R S O LIBERLES RECEIVED MARCH 7, 1960 (8) H. House and D. J. Reif report Xmax 252 mp, c 15,100 for CIphenyl-cis-benzalacetophenone oxide, THISJOURNAL, 77, 6525 (1055). (9) R . E. Lutz and F. W. Wilder, ibid., 86, 2065 (1934). (10) E. P. Kohler and N. K.Richtmyer, ibid., 60, 3104 (1928). (11) See C. Dufraisse and J. Martel, Compt. r e n d . , 246, 457 (1057), for a related rearrangement of one of the photoiixidation products of 2,4,5-triphenylimidazole. (12) F. Klingemann and W. F. Laycock, J . Chem. SOL.,69, 142 (1891). (13) We thank Prof. F. >Beringer I. and Dr. P. S. Forgione for an autheutic sample of VI, F. M. Beringer, P. S. Forgione and If.D. Yudis, Tetrahedron, 8 . 49 (1960). (14) G. 0. Schenck, Angew. Chem., 6 0 , 244 (19481, has reported t h a t tribenzoylphenylmethane (VII) is formed in the photooxidation of tetraphenylfuran. I n view of earlier confusion of VI1 with V I [J. Meisenheimer and K. Weibezan, Ber., 64, 3195 (1921)1, i t is more probable that Schenck's product, like ours, is the enol benzoate, V I .
