Dec. 20, 1958
6685
COMMUNICATIONS T O T H E EDITOR DISPLACEMENT REACTIONS ON THE BI,,Hle UNIT
Sir: We wish to report two transformations of the compound BloH12.2CHaCN' (I) which indicate that the BloH~,unit is transferred from one ligand to another. Treatment of decaborane with diethylcyanamide in diethyl ether a t room temperature produces hydrogen and the air stable and crystalline compound B ~ ~ H I ~ . ~ ( C ~ H &(11) NCN which melts a t 145' dec. (calcd.: B, 34.17; H, 10.19; C, 37.94; N, 17.70. Found: B, 31.32; H, 10.31; C, 37.89; N, 16.65). Approximately one mole of hydrogen is evolved per mole of product formed. The infrared spectrum of I1 contains strong CEN stretching a t 2300 cm.-' (CEN in diethylcyanamide a t 2210 cm.-l). This indicates that the BloHlz unit is attached by the amino nitrogens of the two diethylcyanamide molecules in 11. Treatment of I with diethylcyanamide in refluxing benzene produces I1 in high yield with the displacement of acetonitrile (recovered from run in @-xylene). Decaborane and triphenylphosphine react in diethyl ether a t the reflux temperature to produce a crystalline compound BloHlz.2(CaHs)aP(111) (calcd. : B, 16.78; H, 6.56; C, 67.05; P, 9.61. Found: B, 15.78; H, 6.91; C, 64.13; P, 9.56) which is stable without melting to above 300'. Again, approximately one mole of hydrogen is evolved per mole of compound produced. Both I1 and I11 are recrystallized easily from polar solvents such as methylene chloride. Treatment of I or I1 with triphenylphosphine in hot acetonitrile and benzene, respectively, produces pure 111. Attempts to convert I11 to I1 with excess diethylcyanamide were unsuccessful as were attempts to convert I1 to I by treatment with acetonitrile. The chart summarizes these transformations.
9.5 X loa. The partial structure of I V is tentatively formulated as
IV
The relatively great sizes of triphenylphosphine and the postulated ligand of I V place considerable steric limitations upon the possible bonding sites of the B10H12 unit. It appears clear, however, that the B10H13 unit functions as a discrete electron deficient species. ROHM& HAASCOMPANY M. FREDERICK HAWTHORNE REDSTONE ARSENAL RESEARCH DIVISION R.PITOCHELLI HUNTSVILLE, ALABAMA ANTHONY RECEIVED NOVEMBER 6, 1958 PHOTO-y-TROPOLONE METHYL ETHER
Sir: Irradiation' of an aqueous solution of y-tropolone methyl ether2 (IA) gave photo-y-tropolone methyl ether (11) in good yield. This represents the first instance of photoisomerization in a simple, monocyclic troponoid compound. a
B, R = M A, He
0--q3
I OR I1 OMe Photo-y-tropolone methyl ether (b.p. 34' a t 0.1 mm.), obtained by fractional distillation of the methylene chloride extract of the filtered aqueous solution from the irradiation, showed an infrared maximum a t 5.85 p (but no intense maximum 243 mp (14,900) in the 6.2 p region) and Xk52 and 328 mp (1780). Hydrogenation of I1 over platinum gave a dihydro derivative, 111, 5.85 p and A",? 215 mp (3,200)) and a tetrahydro derivative, IV, (XcmBd:a' 5.75 p ; no high intensity absorption in the ultraviolet). The photoisomer I1 did not show chemical or physical properties characteristic of enol ethers. Dilute acid did not alter 11;however, refluxing I1 in dilute hydrochloric acid for 6-7 hours gave a high yield of y-tropolone (IB) identified by its characteristic ultraviolet spectra in alcohol and 0.1 N sodium hySimilar acid treatment of dihydroLiquid hydrogen cyanide and I1 react slowly a t droxide. room temperature to produce the brilliant red, photo-y-tropolone methyl ether (111) gave 2-cyclo(V). For comparison, 2-cyclohepcrystalline compound B I ~ H w ~ ( C ~ H & N C N . ~ H hepten-1,4-dione CN (IV). (Calculated: B, 29.22; H, 9.18; C, 38.89; (1) Sunlight and mercury arc sources gave the same product. (2) J. Meinwald and 0. L. Chapman, T H I S JOURNAL, 80, 638 (1958). N, 22.69. Found: B, 29.39; H, 9.49; C, 38.51; (3) The naturally occurring alkaloid colchicine has previously been N, 22.54.) The compound I V is extremely to yield three photoproducts (R. Grewe and W. Wolf. Bcr., 84, stable toward water and mild oxidizing agents such found 621 (1951),and P.Santavf, B i d . Lisfr. 81, 246 (1950)). The strucas acetone. Its infrared spectrum exhibits N-H tures of two of the photoproducts are known (E. J. Forbes, J . Chem. (3300 cm.-l) and N=C (1630 cm.-l) stretching. SOC.3864 (1955) and P. D. Gardner, R. I,. Brandon and G. R. Haynes, 79, 6334 (1957)). As in I, I1 and 111, B-H stretching is observed a t THISJOURNAL, L. Nozoe. T. Mukai, Y.Ikegami and T. Toda, Chcm. and I n d . , 2500 cm.-'. In the ultraviolet Am,, 450 mp, E 66 (4) (1955). *s5
(1) R. Schaeffer, THISJOURNAL, 79,1006 (1957).
(5) R.
B. Johns,R . S.Coffey and A. W. Johnson, ibid. 658 (1955).
