1034
VOL.
COhfMUNICATIOh'S
24
sults confirm the conclusion that the hydrat'ion proceeds by cis addition from the less hindered side Hydration Reaction. Hydration of of the double bond.Ib The yields of the cholestanols Unsaturated Steroids were 30% and 40%, respectively, when the hydroboration was carried out by passing diborane into Sir : the sterols dissolved in ether.6 Recently H. C. Brown and co-workers have deCholest wol by either method after acetylation scribed an excellent method for the anti-Markow- furnished 70% of cholestane-3P,6a-diol diacetate nikoff hydration of double boiids, through conver- (m.p. 104-105", [aID +41°) arid 15-20% of sion to the trialkylborane and subsequent oxida- coprostane-38,6d-diol diacetate (1n.p. 136-138', tion. The method used for carrying out the hydro- [ a ] ~16").6 Cholesterol 2-(2'-tetrahydropyranyl) boration step involved passing diborane (generated ether by our modification after acid treatment and from sodium borohydride and boron trifluoride acetylation ga7.e these diacetates in 45% and 35% etherate in diglyme) into a solution of the olefin yield, respectively. It is of interest to note that in an ether' or alternatively allowing the olefin to the direction of attack of the A6-double bond apreact in situ with sodium borohydride atid alumi- pears to depend 011 the bulk of the substituent a t num chloride2 or boron trifluoride3 in diglyme C-3. solution. Other unsaturated steroids have also been hyDiglyme (the dimethyl ether of diethylene glycol) drated by the lithium aluminum hydride-boron not being available to us, we studied the in situ trifluoridc method, as will be reported in the full reaction of olefins with lithium aluminum hydride paper. In addition, the method has been found to and boron trifluoridc in ether solution, since the proceed well and stereospecifically in the decalin latter hydride (unlike sodium borohydride) is ether series, e . g . 7,7. 10-trimethyl-A1(g)-octalingave 7,7,10soluble and this combination is known also to triinethyl-cis-decal-18-01 (m.p. 82-83') in 80% generate d i b ~ r a n e . ~This modification when ap- yicld. plied to simple olefins was found to give as excelThe following hydr:ttion of cholesterol is Lypicd. lent results as the original procedures. Thus I-octene .I solutioii of 0.6 8. of lithium aluminum hydride in and cyclohexene by this method after oxidation 30 cc. of dry ether was added dropwise to a solution with alkaline hydrogeu peroxide furnished I-oc- containing 2 g. of cholesterol and 3.0 g. of boron tanol and cyclohexanol, respectively, in over 80% trifluoridc etherate in 75 cc. of ether under nitrogen. yield. In this way the necessity of generatiiig di- After 1 hr. at room temperature, the mixture was borane separately, or using the high boiling diglyme treated with 21 saturated sodium sulfate solution [b.p. lCiO-lG2" (740 mm.)] in sztu is arroided. aiid solid sodium sulfate, and wus filtered and We have successfully :tpplied the Brown hydra- evaporated. The residue in tetra hydrofuran \vas tion method to steroids. I3y USP of our modification, lhen oxidized with 30% aqueous hydrogen perA*-cholesteric gave 60%;: of chol(~stan-4a-ol [m.p. oxide a i d :ilcoholic sodium hydroxide, arid the 187-188", [ a ] I ,+3" (ull rotations in chloroform) ] product wts isolated with ether, acety1:tted and and As-cholestene gave 75yc of eholestnn-6a-01 chromatographed on alumina. (m.p. 128-129", [ a ] U +So). 50ihomeric dcohols 1IANIT.L SIE FF RMEARCHINsTITUTh SA^ I , W O L I ~ ~ ~ were detected (the remainder was mainly un- \ v E I Z A l A N N INSTIlUTC O F SCI St \ N A Y Y E XIJSSIM OTH, Y X I i U D A 11IZUR changed starting material in each case)and these re- I ~ L ~ I O VISRAEL
A Convenient Modification of t h e Brown
+
(1) H. C. Broim wid B. C. Subba Rao, J. Org. Chenz., 229 1136, 1137 (1957); ( b ) H. C. Brown and C.Zweifcl, J . Am Chenz. Soc., 81, 247 (1950); (c) It. Dulou and Y. ChrdtienBessibe, Compl. rend., 248, 416 (1059) (2) H. C. Brown and B. C. Subba Rao, J . A m . C h e m Soc., 78, 5694 (1956); R. I'appo, J . Am. Chenz. Soc., 81, 1010 (1959). (3) H. C. Brown and G. Zweifcl, abstracts of papers, 135th Meeting of the American Chemical Society, Boston, Mass., April 1059, p. %-O. (4) I. Shapiro, 1%.G. Weiss, hi. Schmich, S. Skolnik, and G. B. L. Smith, J . Am. Chem. Soc.. 74,901 (1952).
$'ktuiL
SoxYnIrEIMER
Received June 15, 1959 -
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( 5 ) The rest of thc material was :tgain unchanprd starting material in each case despitc a largc ( w e s s of dihorane being used. The yield could therefore probaW be irnproved by UHC of an even larger excess. ( 6 ) These results are in accord with those reported independently by W.J. Rechter [Chrm. t& Ind. (London),294 ( 1959)]. (7) N. R. C. Postdoctoral Overseas Fellow, 1957-58.
