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C O M h I U N I C . 3 T I O N S TO T H E
EDITOR
Vol.
is
: CHS-CH.2. (I) ,CHX-CHr: (la) of IV with acetic anhydride in pyridine yielded IT, m.p. 263-263° (Calcd. for C14H&06: C, 57.73; \Vith excess of monomer both ends of I or Ia H, 4.50; N, 4.81. Found: C, 3T.43; H, 4.12; N, 5.10). The infrared absorption spectrum and propagate polymerization, each by a different melting point of the synthetic product and of the mechanism, one end growing as a radical, the other compound obtained by degradation of novobiocin as a carbanion. After addition of the first monomeric unit t o either end, structures I or I a become were identical. 2,2-Dimethylchroman-6-carboxylic a ~ i dwas ~ , converted ~ with thionyl chloride perfectly legitimate, i.e., a true separation of elecinto 2,2-dimethylchroman-6-carbonyl chloride, n1.p. trons takes place and species like I1 are formed. 95-97'. Treatment of the amine hydrochloride : CHS--CH?-CHX-CH?. or IV with this acid chloride in pyridine gave cyclo:CHX-CH?-CH?-CHX. (11) novobiocic acid (VI), m.p. 280-2884". Aimixture of this product and VI obtained by degradation of The radical ends do not long exist. At low novobiocin melted a t 280-2SG0, and the infrared temperature they dimerise, and consequently absorption spectra of the two were identical. species I11 are formed .l-Xcetoxy-3-(3-methylbutyl) -benzoic acid,4 m.p. : CHS--CH2--CH?-CHX : (111) 147-1849', was converted with thionyl chloride into 4 - acetoxy - 3 - (3 - methylbutyl) - benzoyl chloride. Inspection of species I11 suggests t h a t they do Upon treatment of IV with this acid chloride in not terminate, and thus propagation should pyridine, followed by hydrolysis, dihydronovobiocic continue until all the monomer is consumed, and acid (VII) was obtained, m.p. 23'7-2339". ;Z mix- eventually a "living" polymer is produced. ture of this product and VI1 obtained by degradaThe correctness of all these assumptions has been tion of novobiocin melted a t 237-239". The iden- tested. Polymerization, if carried out correctly, tity was confirmed by the infrared absorption spec- always goes to completion. The green color of tra. naphthalene- ion instantaneously changes into deep CLACDE F. SPESCER red on addition of styrene, the latter color due CHARLES H. STAMMER MERCKSHARP & DOHME Xfter completion of polymerizaRESEARCH LABORATORIES J O H N OTTORODIY to styrene- ends. tion the red color persists, indicating no reverse DIVISIONOF MERCK& Co , Ixc EDWARD ~I'ALTOX RAHWAY, SEW JERSEY FREDERICK II' HOLLY of reaction (2). If an additional amount of styrene KARLFOLKERS is added after completion of the polymerization of RECEIVED MAY9, 1956 the first portion, the polymerization starts again, and the reaction goes again to completion. The viscosity of the polymer solution can be POLYMERIZATION INITIATED BY ELECTRON A NEW METHOD OF measured without withdrawing the solution out of TRANSFER TO MONOMER. FORMATION OF BLOCK POLYMERS' the reaction vessel. Xddition of further amounts of Sir: styrene and of solvent, quantities of which are *iromatic hydrocarbons react with metallic adjusted in such a way t h a t the ratio styrene: sodium in suitable solvents yielding colored and solvent remains unaltered, leads to an increase in soluble complexes of composition 1 S a to 1 hydro- the viscosity of the solution. For example, carbon*which initiate polymerization of conjugated styrene (9.2 g.) was added to 60 cc. of tetrahydromole of sodium napholefinic hydrocarbons.3 Their structure has been furan containing 3.3 X elucidated by IVeissman and Lipkin,l who showed thalene. Polymerization was carried out a t -80" them t o be composed of negative aromatic hy-dro- and after completion the viscosity of the solution carbon ions and K a + ions. They have shown also was determined a t room temperature (1.2-1 ..? that the negative hydrocarbon ions act as electron sec.). The solution was recooled to - S O " , and an additional '7.7 g. of styrene in 30 cc. of tetrahydrotransfer agents, e.g. furan was added. Xfter completion of the reaction Saphthalene- + Phenanthrene J_ the viscosity was found to increase to 18-20 sec. a t Phenanthrene- + Saphthalene (1) room temperature. The final yield was IO.(; g. of \Ve postulate the same type of electron-transfer polystyrene, i.e., about 100T conversion. This process t o be responsible for the initiation of poly- proves conclusively the existence of living ends in these polymers, and suggests a n interesting and novel merization by sodium-naphthalene complex, e.g. method for preparation of block polymers. .After Saphthalene- + Styrene -+ completion of the first polymerization process, Styretie- + Saphthalene (2) a second Inonoiner is added t o the still living The negative monomer ions formed by reaction polymers formed from the first monomer. Thus, block polymers of the type .A .A 1.R .R ., .B .*LA., ..I (2) may be represented formally by I or 1a.j are produced. For example, tyrene (5.7 g . ) (1) This research was partially supported by a grant from the Office was polymerized by 0.3 millimole of catalyst in the of Naval Research Contract Sonr-131091. .6 g. of isoprene was added. usual way and the (2) N. D. Scott, J . 1'. \Valkrr and V. I.. Hansley, THIS~ouxvsl., g. of polymer was obtained. Xfter precipitation 68, 2442 (1930). The polymer solution in toluene could not be pre(3) N. D. Scott, U. S.Patent 2 , 1 8 1 , 7 7 1 ( I 9 3 Q ) . (1)D. E Paul, D. Lipkin and S. I . IVeisiman, T H I S J O I J R S A I . , 78, cipitated by isooctane, proving the absence of pure 1 1 R (1950). polystyrene. On the other hand, the polymer is ( 5 ) This is only a formal notation. Styrene- should be visualized not extractable by isoSctane, proving the absence a s a species possessing an additional electron in t h e lowest li orhital of pure polyisoprene. Thus, the nature of the which is unoccupied in t h e ordinary molecule of stl-rene.
June 5 , 1956
COMMUNICATIONS TO THE EDITOR
block polymer is established. Many other block polymers were prepared by this technique. The naphthalene-sodium initiator gives block polymers of the type A.B.A, or A.B.C.B.A.6 The presence of two living ends was proved b y experiments which will be reported later. However, the same method can be applied t o conventional initiators of anionic polymerization yielding block polymers of the type A.B. or A.B.C. ( 6 ) I n these a n d in t h e following formulas letter A, B and C stand for blocks of monomers, i . e . , A ....A, B ....B , or C . . . C.
2657
and methyl vinylacrylate in benzene, was smoothly converted by aluminum isopropoxide in hot isopropyl alcohol t o the hydroxylactone (IV) (m.p. 122-123”, found: C, 68.79; H, 6.50)) which with bromine in methanol, followed by sodium methoxide, gave the methoxylactone (11). CONVERSE MEMORIAL LABORATORY HARVARD UNIVERSITY CAMBRIDGE 38, MASSACHUSETTS
R B \VOODWARD F E. BADER H BICKEL .\. J FREY R . \ir.KIERSTEAD
APRIL 19, 1956 RECEIVED CHEMISTRY DEPARTMENT OF FORESTRY M. SZWARCINVESTIGATION OF SYNTHESIS VERSUS REENTRY COLLEGE STATE UNIVERSITY OF SEW YORK M. LEVY IN TWO ORGANIC NITROGEN CONTAINING R . MILKOVICH SYRACUSE 10, S . Y . SYSTEMS UNDER NEUTRON IRRADIATION’ RECEIVED MARCH29, 1956 Sir :
A SIMPLIFIED ROUTE TO A KEY INTERMEDIATE IN THE TOTAL SYNTHESIS OF RESERPINE
Sir: Recently we recorded’ the total synthesis of reserpine (I), throuqh a route involving the meth-
H
,OMe
MeOOC/
H
H OMe 1
oxy-ether (11)) which was prepared from the p benzoquinone-vinylacrylic acid adduct (111, R = H) b y a five-stage process. We now wish t o report
I1
III
that the key intermediate (11)) which contains all jive of the asymmetric carbon atoms of Ring E of reserpine, properly oriented, is readily preparable from the p-benzoquinone-methyl vinylacrylate adduct (111, R = Me) in two simple operations. The adduct (111, R = Me) (m.p. 103-104”, found: C, 65.07; H, 5 . 5 7 ) , from p-benzoquinone
op A / O H I /”*H
0
Iv (1) R. B. Woodward, F. E. Bader, H. Bickel, A. J. Frey and R . W , Kierstead, THISJOURNAL, 78, 2023 (1956).
Previous work by the authorsZ has shown that both anthracene-C14 and acridine-C14 are produced by the neutron irradiation of acridine. These products are formed by reentry3 of the recoiling carbon-14 which travels a considerable distance after being “born.”4 It became increasingly evident from our work on this and other systems that the inordinate difficulty in bringing the products to radiochemical purity was possibly due t o synthesis5 products which were difficult t o remove because of their presence in the parent compound. I n most cases it would be reasonable t o expect their chemical behavior t o be similar to that of the parent compound. Trace degradation products may also be important. We have irradiated benzene in 2-methylpyrazine, and acetamide, in the Brookhaven Reactor. The presence of two possible synthesis products, toluene and propionamide, mere then investigated by carrier methods. I n the case of acetamide, both propionamide and propionic acid were added as carriers on the assumption that the synthesized, excited three carbon fragment might in some cases collapse t o give propionic acid. The hydrolysis was carried out both in acid and base t o investigate possible differences in the state of the irradiated material. Degradations were carried out by the method of Phares6 The results are given in Tables I and 11. While it is clear from these results that synthesis does take place, it becomes evident that the reaction
to give toluene or propionamide involves processes other than a simple displacement by a “hot” methyl radicaL7 The activity in the methylene, carboxyl, and ring carbons of the carrier materials studied cannot be credited to an inversions reaction, al( 1 ) Research performed under t h e auspices of t h e U. S. Atomic Energy Commission. ( 2 ) A. P. Wolf and R . C. Anderson, THISJOURNAL, 77, 1608 ( 1 9 i 5 ) . (3) W e prefer ~ e e n t i yt o retention in describing this process in order t o avoid t h e implication, in t h e case of anthracene, t h a t t h e molecule containiug t h e ”4 undergoing nuclear transformation is t h e same molecule which then contains t h e ‘ 2 1 4 in its ring. (4) W. F. Libby, THIS JOURNAL, 69, 2523 (1947); H. Faraggi, A n n . P h y s . , 6 , 3 2 5 (1951). ( 5 ) By synthesis we mean a n y product formed which has one carbon m o y e t h a n the parent compound exclusive of t h e carbon analog of t h e parent compound. See also A. G. Schrodt and W . F. Libby, THIS JOURNAL, 76, 3100 (1954); L. J. Sharman and K. J. McCallum, ibid., 77, 2989 (1955). (6) E. F. Phares, AYch. Biochem. Biophys., 33, 173 (1951). (7) J. E. Willard, A n n . Rev. P h y s . Chem., 6 , 141 (19.55). ( 8 ) J. F. Hornig, G. Levey and J. E. Willard, J. Chsm. P h y s . , 20, 1556 (1952).
