[COSTRIBUTION FROM THE INSTITUTE OF ORGANIC CIXEXIXSTRY O F THE UNIVERSITY OP BUDAPEST]

DIMERIC PROPENYL PHENOL ETHERS. XVI. FORMULATION OF THE BCID-CATALYZED DIMERIZATION OF THE

PROPEKYL PHENOL ETHERS

ALEXANDER MULLER

Received Octobei 8, 1961

Structural investigations on dimeric propenylphenol ethers have shown (1-6) that these substances belong almost invariably to structural types that are common to those of other dimeric styrene derivatives. Therefore, contrary to earlier views (7), no essential difference would seem to exist between the propenyl- phenol ethers and other a-aryl ethylenes with respect to the mechanism of their dimerization. TiF'ith considerable material on the structures of these dimers now at our disposal, the present paper attempts to give a detailed formulation of the acid-catalyzed dimerization of a-aryl ethylenes from the structural point of view.

The fact that these dimerizations require the presence of acid in order to effect proton release and that their rate appears to be dependent upon the concentration of the acid present in the reaction mixture (cf. sa), sharply characterizes the process as representing a single elementary act of cationic poly- merization (cf. 8b), which proceeds through the usual concerted phases of (a) initiation, (b) propagation, and (c) cessation (cf. 9). These phases might be fol- lowed eventually by a secondary act of rearrangement.

(a) For acid-catalyzed dimerization it is a prerequisite that the monomer be sufficiently polarizable by the acid acting as catalyst. Styrene, which dimerizes readily, loses this ability when alkyl-substituted on the p-carbon atom, since such substitution decreases the polarizability of the double bond. The stabilizing effect of the p-alkyl will be counteracted by simultaneous p-alkylation or p-methoxyla- tion of the aromatic ring which effects an electron-shift in the system toward the p-carbon.

If, therefore, the double bond of the monomer is sufficiently polarizable, acids convert a number of monomer molecules (I) to monomeric carbonium ions (11) by proton donation to the p-carbon (10). This decreases the activation energy of the system to a point where chain-initiation is likely to occur. In the carbonium ion the bond between the proton and the p-carbon is rather weak. Owing to the hyperconjugation of the C8-H bonds with the now electron-deficient a-carbon, dissociation readily occurs, and this creates a dynamic equilibrium between the monomeric ion and the unchanged monomer in the reaction mixture. The exist- ence of such equilibrium was clearly demonstrated by Yoshida (10) in the dimeri- zation of styrene or of anethole in the presence of deutero hydrochloric acid, where not only the resulting dimer but also the monomer regenerated from the reaction mixture were each found to contain one atom of deuterium per mole.

The role played by the cis or trans distribution of the substituents on the C , C double bond seems not to have received close investigation. Although differences in the rate of proton addition are very likely (cf. 11), such differences would not

1077

1078 ALEXANDER MULLER

be expected to affeci substantially the structure or the configuration of the resulting dimeric products (cf. 12), since the steric distribution of the substituents would soon be equilibrated in the reaction mixture (13), in as much as the steric relationships in the carbonium ion are mobile, rather than fixed.

( b ) The monomeric carbonium ion (11) now acts as an electrophilic system competing with the protons in the addition to unchanged monomer molecules. The addition of tbe carbonium ion creates a C , C bond between the carbons a and 0’ of the two originally independent systems, and the results in the forma- tion of a dimeric ion (111). This transfer of the positive charge from carbon a to the carbon a‘ of the second monomer unit stabilizes the hitherto labile CB-H bond, and the originally stable C”-W bond now comes into hyperconjugation -4th the new carbonium carbon.

Like the monomeric ion, the dimeric ion also is a highly reactive system which seeks stabilization, either by addition to an unchanged monomer molecule, or by expulsion of a proton. If, however, proton release for any reason is momen- tarily deferred, the dimeric ion competes with the monomeric ions and protons for unchanged monomer molecules, and thus tends to build up trimeric and then, gradually, higher polymeric ions until finally, there occurs a proton loss which then gives a polymeric end-product. If, however, t8he proton is expelled instantly after the addition of a monomeric ion to the monomer, a dimeric end-product is obtained.

(c) Under the conditions usually employed for the dimerization of styrene derivatives, the release of a proton from the dimeric system is not hindered and this, therefore, efficiently prevents further propagation. Such is the case when unchanged monomer molecules are no longer available in adequate number for further addition, which can easily be achieved by the simultaneous protonation of a comparatively large number of monomer molecules through the use of a sufficient quantity of moderately dilute mineral acid.

In the case of a-arylethylenes, cessation of the chain-reaction might have two distinctly different mechanisms. (cl) Usually a single proton will be detached from the particularly unstable CB’-H (or, as it may be referred to here, the Cz-S) bond of the dimeric ion. The zwitterionic intermediate (IQ) is short-lived, being stabilized by creation of a second bond between carbons 1 and 2 (addition of car- bon 1 to carbon 2 , i e . , regeneration of the double bond of the second monomer unit), with formation of an olefinic end product. (cp) Another possibility for cessa- tion arises in those cases where the polarizability of the 3-aryl group has been effected by the carbonium carbon within the system. Owing to the rotation of the carbon chain in the dimeric ion, oiily a t intervals does t,he carbonium carbon come close enough t o the 3-aryl group to effect an electromeric displacement there by its proximity. Since a sufficient electron density on carbon 6’ of the 3-aryl group might lead t o interaction between the carbons 1 and 6’ (IlI%), the 3-aryl group therefore would compete with carbon 2 for bond formation with the carb- onium carbon. I n case of actual interaction an entirely new C,C single bond would be created. Simultaneous or consecutive loss of proton from carbon 6’ then would lead to the formation of a cyclic end-product.

DIMERIC PROPENYL PIlEiYQL ETHERS. XVI 1079

The ratio between the respective probabilities of the two terminating mecha- nisms depends upon the relative polarizability of the Ce’-H bond of the 3-aryl, and its consequent influence upon the rotation of the carbon chain in the dimeric ion-which, in turn, is dependent upon the nature of‘ the substitution of the @-carbon of the monomer, and the particular conditions in the reaction mixture. Therefore, an appropriately located alkoxy1 (hydroxyl) substitution of the aromatic ring of the monomer would greatly increase the otherwise slight prob- ability of a 1,6’-bond formation in the primary terminating reaction.

The process of acid-catalyzed dimerization will be thus recognized as repre- senting no simple addition of the one monomer unit to the double bond of the other. Addition “. . . rarely, if ever, proceeds by direct addition of a molecule across a double bond. Instead, the reaction appears to occur by step-wise addi- tion of part of the addendum first to one side of the double bond and then the remainder to the other” (14). In the present processes, the double bond of the starting monomer molecule first adds one proton to its @-carbon .from the reaction mixture, and then adds with its a-carbon to a second monomer molecule that will, in consequence (in polymerization only after undergoing interlinkage with further monomer molecules), lose one proton to the reaction mixture. That is, the double bond adds to the fragments of two diflerent systems that-except when the process is intramolecular-do not belong integrally to the same molecule, al- though formally it might seem that they do. Processes such as this may be re- ferred to as hetero additions.

I n the cationic dimerization (polymerization) of a-arylethylenes the double bond of the starting monomer molecule (and also the double bonds of all monomer units attached later, save the last) invariably disappears by such intermolecular hetero addition, while the double bond of the second (last) unit either will be regenerated or will disappear (according to the actual mechanism of the stabiliza- tion of the system) as a result of intramolecular hetero addition, where the one fragment added to the p-carbon is the electrophilic carbonium ion and the other added to the a-carbon is the adjacent p-carbon or the more distant 3-aryl group.

The process is illustrated by scheme on page 1080 (with anethole as example). While the readiness toward cationic dimerization depends upon the polarity of

the double bond under the influence of the aromatic ring of the a-arylethylene, the frequency of the terminating mechanism c2 in stopping the chain-process depends upon the polarizability of the aromatic ring itself.

Styrene (15, IS), or its derivatives substituted with methyl (8, 17, 18) or phenyl (19) on the a-carbon or alkylated in the aromatic ring (20, 21) but in all cases unsubstituted on the p-carbon, in acid-catalyzed dimerization usually form the olefinic dimer as the primary product (cf. 22). The permanent effect of hypercon- jugation in the dimeric ion outweighs by far the electromeric effect of the car- bonium carbon upon the distant 3-aryl group, since the low intrinsic polarity of that group would not seriously hinder the rotation of the carbon chain. Therefore, the chance of C1, C6‘-bond formation here is, of necessity, low.

The stability of the olefinic dimer (VII) is however relative, and would greatly depend upon the polarizability of its C1,C2 double bond. I n the case of the p-

1080 ALEXANDER M ~ ~ L L E R

unsubstituted a-arylethylenes, the olefinic dimer generally remains suceptible to polarization by even as moderate an electrophilic substance as the mineral acids. Therefore, under the conditions prevailing in the reaction mixture during

I

H

/\ H An

VI I1 (trans, trans-Met anethole)

7‘

4, R T H N

@~H-C’ICX& T

0-7H-C13CE13 ,T

4-121 Polymerioion +--- CHaQ B’CHCH,

GEiAn I R +CHAn

HI, ITI;

E1 H

-4 CHIO -:CCHa

p;n--c--Ip I CHAn -k

IV V (trans-Hsoanethole

dimerization, the olefinic dimer might undergo repolarization, and this would create a dynamic equilibrium between the dimer and its carbonium ion. Repolari- zation of the system VII re-opens the chance to stabilization by 1,U-bond forma-

DIMERIC PROPENYL PHENOL ETHERS. XVI 1081

tion. Although the regenerated dimeric ion again n-ould lose its proton pre- dominantly from carbon 2, some carbonium ions would be lost from the equilibrium by 1 ,6'-bond formation. Owing to this circumstance, the latter mechanism-although almost unassisted by the 3-aryl group-might use up the dimeric ions constantly regenerated from the olefinic dimer, in spite of the in- frequency of its oecurrence. For a given time and a given concentration of the catalyzing acid, the ratio between the olefinic and the cyclic product therefore would depend upon the rate of the irreversible stabilization which followed, the proportion of the cyclic form increasing with the time of the actual contact with the catalyst. F Q ~ this reason, the monomeric styrene derivative, although primarily forming the olefinic dimer in predominant proportion, might be con- verted-if the rate of irreversible stabilization was not impractically lorn-to the cyclic dimer. This known fact (23) recently was demonstrated exactly by Spoerri and Rosen (24) who found that: (a) 1,3-diphenylbutene-1 (olefinic distyrene, VII) (15) would rearrange (cf. 16) to 1-phenyl-3-methylindan (cyclic distyrene, IX); ( b ) styrene would produce the cyclic dimer IX in about 70% yield-if only adequate time in contact with the acid catalyst for interaction was allowed. Similar observations were made earlier, with less precision, with a-phenylstyrene (19), a-methylstyrene (8), p-alkylstyrenes (20, 21), etc.

-k H+ c-- - N*

PhCH +

-- VI1 VI111 1'

Ph P h

IX VI412

Although alkyl substitution on the ,&carbon stabilizes the styrene molecule against acids (cf. 25) by counteracting the electron-displacing effect of the phenyl group, the simultaneous presence of a p-methoxy group in the aromatic ring of anethole inhibits such stabilization. Therefore, anethole readily dimerizes in the presence of acids. In this process the olefinic dimer (isoanethole, V) again will be predominant, since the intrinsic polarity of the p , p'-disubstituted aromatic ring is rather low. However, in all methodical variances of anethole dimerizat.ion (cf. 2) varying quantities of the easily separable simultaneously formed cyclic

1082 ALEXANDER MGLLER

dimer (metanethole, VI) also are obtained, the quantity of which would, in con- tradistinction to the preceding case of the @-unsubstituted styrenes, not increase, a t least not substantially, on prolonged contact with the catalyst (2). Evidently, the double bond of the olefinic dimer here formed will not be polarized under the conditions prevailing in the reaction mixture, and so the stabilization of the dimeric ion 111 by 1,2-bond formation proves to be irreversible in this case.1

Comparing propenylbenzene (A), p-methoxypropenylbenzene (B), olefinic distyrene (C), and isoanethole (D), i t is obvious that the double bond in propenylbenzene would be activated by adequate substitution of the p-methyl in C, while a second substitution of the same carbon will counteract that activation (D).

A PhCH=CHC& N

R AnCH=CH-CJ& H

/cH* -/ \

C PhCH=C D AnC€I=C

CHAnGHnClIL CHPhCIF, \

The stability of the double bond of isoanethole is of course dependent on the polarizing effect of the actual catalyst. Whilst dilute acids are apparently unable to affect adequate polarization, the more electrophilic metal haloids of the Friedel-Crafts type [stannic chloride (2, 26), aluminum chloride (27) , titaniumIY chloride (28), etc.] add readily to the system with the formation of more or less insoluble complexes. Such an addition turn3 isoanethole into a carbonium ion (X) analogous t o the dimeric ion (111) which is formed from anethole in the presence of acids, aave for the difference that here carbon 2 is attached t o a metal haloid. [Somewhat different views on the nature of this bond, and the possible role of moisture as co-catalyst in its formation, are revealed in the literature (9)]. In conse- quence, this repolarization of the double bond opens only the 1,6’-bond formation of the normally two alternatives t o the subsequent stabilization. Since the rate of 1,6’-bond formation is small, the metal haloid containing carbonium ion-no chance being given t o 1,a-bond formation-would seek t o acquire stability by way of propagation which does not require an instant loss of proton. Therefore, if unchanged isoanethole is present, the ion might build up polymeric ions before actual stabilization. This explains the experience that part of the starting material will polymerize in this process [cf. (2), see also (9)], t o which it is the natural consequence that subsequent hydrolysis of the resulting metal haloid complex (cf. 30) affords metanethole in a yield not appreciably exceeding 10% (2,26,27,28). The product is in every respect identical with that obtained from anethole by dimerization.

v 1 SnCIn

CHCHaCB

Polymeric ion +- n T’ CHsO ()--+ CH8 C--+ SnC&

i - 7CHAn

s,

DIMERIC PROPENYL PHENOL ETHERS. XVI 1083

This provides the evidence, that in the acid-catalyzed dimerization of CY-

arylethylenes two cessation mechanisms (c1 and ce) are simultaneously operating, which, however, is fully apparent so far only in the dimerization of anethole. The alternate possibility, that in this case also the cyclic dimer would arise from a secondary rearrangement of the olefinic dimer, except that the rate of re- arrangement triould appear to be substantially decreased, seems to be excluded with respect of the main reaction. Baker and Enderby ( 2 ) presented evidence that boiling 40y0 aqueous sulfuric acid, which converts anethole within seven hours quantitatively into a 3:1 mixture of isoanethole and metanethole, is unable to produce appreciable quantities of metanethole from pure isoanethole within the same period of time. Both the crystalline (m.p. 40-40.5') and the liquid form of isoanethole, which are considered to represent the trans and cis isomer, differing in the relative steric distribution of the 1-p-anisyl and the 2-methyl. group (26), display identical behavior in this respect, in evidence that-under the conditions of acid-catalyzed dimerization-neither of the two forms would act as an intermediate in the formation of metanethole. A secondary rearrange- ment of isoanethole would depend under particular circumstances upon the degree of polarization actually attained. This seems to be insufficient in dilute mineral acids, but is raised sufficiently by Friedel-Crafts metal haloid catalysts. In the latter reaction therefore both forms of isoanethole undergo rearrangement, the respective rate being then dependent upon the steric distribution of the sub- stituents on the double bond (26).

I n acid-catalyzed dimerization it is the life span of the dimeric ion 111 which seems to determine the proportion of the cyclic dimer that will be found in the dimerizate. Baker and Enderby made the observation that, while the yield of metanethole in the dimerization of anethole by alcoholic 2040% hydrogen chloride is dmost negligible (l), it rises to 2446% if the process is conducted in

H CHCHzCHa

CH3 C---+ SnC14

+CHAn -

XP I

H' 'An VI

XI

1084 ALEXAKDER MULLER

43% aqueous sulfuric acid. [Isoanethole was found to remain unchanged in both instances @).I For this difference the interpretation is offered here, that sub- stitution of alcohol with water improves the conditions for ionization, and thereby extends the life of the dimeric ion 111. Since the occurrence of 1,6'-bond formation depends on the frequency of the intermittent proximity of the carbonium carbon and the 3-aryl group, the prolongation of the life span of the ionic state represents an increase in the probabjlity that stabilization might occur by mechanism c2.

Those propenylphenol ethers that are alkoxyl (hydroxyl) substituted in the 3- or 5-position of the aromatic ring-such as isoeugenol, isochavibetol, their alkyl ethers, and asarone-produce in an acid-catalyzed dimerization the cyclic form of dimer to such a preponderant extent that their olefinic dimer is not even known. Only in the dimerization of isosafrol (cf. 31), where the activating effect of the 3,4-methylenedioxy group upon the aromatic ring is less pronounced (321, has the formation of an olefinic dimer also been reported (4). No doubt, in these cases the aromatic ring has a high intrinsic polarity, owing to the hereto appropri- ate situation of the 3- (5 - ) alkoxyl (hydroxyl) group.2 The high electron density on carbon 6' of the dimeric ion r i l l greatly reduce the rotation of the carbon- chain, and the probability of 1,B'-bond formation will now not only compare with, but actually outweigh, 1 ,%bond formation in the terminative phase. It is rather difficult to estimate the extent of a simultaneous 1,2-bond formation and its eventual contribution to the proportion of the cyclic end-product by way of a secondary rearrangement. The olefinic dimer is presumed, even in the case of its conceivable transitory formation, to be highly unstable under the conditions of dimerization.

As to the stereochemistry of the dimerization process, the intermediates cannot be expected to acquire definite steric configuration, so long as they remain in the ionic state, save perhaps by a somewhat hindered rotation around the C2-Ca axis. The definite configuration of the end-products-observed in the olefinic dimers of anethole (26), and in the cyclic dimer of anethole (28) and isohomogenol (33)- appears to be forced upon the system in the last phase of the process, where

This effect is discernible in the recently discovered (4) formation of small amounts of 2,3,6,7-tetramethoxy-9,10-diethy1-9,l0-dihydroanthracene (XIII) in the usual preparation of diisohomogeenol from isohomosenol. The mutual ~olarization of two monomeric car- - - bonium ions ( X I ) might lead to intermolecular carbonium carbons and aromatic rings, followed (cf. 6).

bond formation between the respective by subsequent double release of proton

XI1

DIMERIC PROPENYL PHENOL ETHERS. XVI 1085

the formation of a new C,C bond will create a double bond, or form a rigid ali- cyclic ring. Both processes mill fix the relative steric disposition of the sub- stituents on the carbons involved.

(a) In the simultaneous formation of a mixture of two stereoisomeric forms of the olefinic dimer, the factors predetermining the definite preponderancy of the one isomer over the other are a t present not perfectly clear. In the dimerization of anethole, Baker and Flemons (26) find that at least 8001, of the yield of iso- anethole is accounted for by the crystalline isomer of m.p. 40-40.5" which in the reaction with stannic chloride would form metanethole more smoothly and in somewhat greater yield than the liquid form. This relative instability of the crystalline form against polarization well agrees with the cis position of the p - anisyl and the a-p-anisylpropyl groups on the double bond, suggested by the authors. Marion (34) proposed the analogous spatial structure for olefinic distyrene. Closer evidence on this question would appear, however, desirable.

(b ) In case of the cyclic dimers the substituents of the completely disappearing double bond of the second monomer unit were found invariably to come into trans position relative to each other. It appears that for ring formation the co- existence of the 2-methyl- and the bulky 1-aryl group on the same side of the planar ring-system would be less favorable. Although the bulk of the alkyl sub- stituents of the carbons 2 and 3 may play a much smaller role in the relativesteric orientation, this factor seems to secure the prevalence of trans orientation also on these carbons.

SUMMARY

The process of the acid-catalyzed dimerization of the propenylphenol ethers is formulated, in correlation with that of P-unsubstituted styrenes, as a primary process of cationic polymerization, that is followed under the circumstances of the reaction by a secondary process of rearrangement. The mechanism of the terminating reaction is discussed as to its dependency upon the intrinsic polarity of the a-aryl of the monomer.

,MUZEUX K ~ R U T 4/b, BUDAPEST VIII, HUNGA~Y

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Ber., 76, I l l9 (1943); Part VIII, M ~ L L E R , Ber., 77, 159 (1944). (4) PAILER, Monatsh., 72,45 (1947). (5) PAILER, U. M ~ L L E R , AND PORSCHINSKI, Monatsh., 79,620 (1948). (6) VON E. DOERING AND BERSON, J . Am. Chem. Soc., 72, 1488 (1950). (7) TIEXANN, Ber., 24, 2870 (1891); ROBINSON, J . Chem. Soc., 107, 267 (1915); HARASZTI

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(8) (a) SCHMITZ-DUMONT, HAMANN, AND DIEBOLD, Ber., 71, 205 (1938); (b) BERGXANN, TAOBADEL, h N D WEISS, Bey., 64, 1493 (1931).

(9) Cf. H A M ~ X , Angew. Chem., 63, 231 (1951). See also: PRICE, Ann. N . Y . Acad. Sci., 44, 381 (1943); HZILBURT, H.~RMAN, TOBOLSEY, AND EYRIXG, Ann. Ib;. Y . Acad. Sei., 44, 351 (1943); WILLIAXS AND THOMAS, J . Chem. Xoc., 1867 (1948).

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(11) CH-~VANNES, Rev. gdn. sci., 86, 299 (1924). (12) Part I, MULLER, RALTSCXEWA, LYD PAPP, Ber., 78, 629 (1942). (13) BOEDECKER AND VOLE, Ber., 64, 61 (1931); FUNAKCBO, Ber., 74, 832 (1941). (14) ALEXANDER, Principles of Ionic Organic Reactions, p. 135, J. Wiley and Sons, New

(15) FITTIG A~YD EXDWA", Ann,, 216, 187 (1883); STOBRE AND POSNJAZ, Ann., 371, 287

(16) STOERJ~ER AND KOOTZ, Bel.., 61, 2330 (1928). (17) KLAGES, Ber., 95, 2639 (1902). (18) TIFFENEAU, Ann. chim. France, [8] 10, 158 (1907). (19) SCHOEPFLE AND RYAN, J . Am. Chenz. Soc., 62, 4021 (1930); BERGMA" m D WEIS&,

(20) KLdGES, Ber., 36, 2253 (1902). (21) &-RANEN, Ann. Acad. Sci. Fennicas, Ser. A , No. 10, 1 (1933) [Chem. Cenir., 11, 865

(22) SCHYITZ-DUMOST, TH~WKE, AND DIEBOLD, Ber., 70, 178 (1937). (23) EISI LYD GALTIN, Can. J . Research, [B] 14, 255 (1936); cf . STANLEY, C'hemistry & 1%-

dustry, 58, 1080 (1939); MARION, Car&. 3. Research, [B], 18, 309 (1940). (24) SPOERRI AND ROSEN, J. Am. Chem. Soc., 72, 4918 (1980). (25) Cj. SCHLENK (7)) vol. 2, p. 550; ERRERA, Gam. chim. ital., 14, 509 (1884). (26) BAKER - 4 ~ 0 FLERIONS, 3. Chem. soc., 1984 (1948). (27) vm DER ZANDEN .LVD DE VRIES, Rec. trav. chim., 68, 261 (1949). (28) Par t XIII, MULLER, h ~ f i s z h o s , LEMPERT-SRI~TBR, AVD SZARA, 3. Org. @hem., 16,11003

York, 1950.

(1909).

Ann., 480, 49 (1930); c f . SCHLENK AND BERGSIANS, Ann., 479, 65, 76 (1930).

(1933)l; HUKEI, Acta Chem. Scaad., 3, 279 (1949).

(1951).

73 (1935). (29) ST-4CDINGER AND BRECSCH, Re?"., 62, 442 (1929); STAUDINOER . U D DREHBR, Ann., 61'8,

(30) C j . STAUDINGER, Die hochn~olelcularen organischen Verbindungen, Verlag J. Springer, Berlin, 1932; PRICE, ilfechanism of Reactions at Carbon-Carbon Double Bonds, p. 113, Interscience Publishers, Xew York, 1946; See also: MAGEE, STAND, AND EYRINQ, J . Am. Chem. SOC., 63, 677 (1941); MEYER AND MARE, Makronwlelcdare Chenzie, 2nd edition, p. 205, =Ikademische Verlagsgesellschaft Geest and Portig, Leipzig, 1950.

(31) Cj . TAKEBAYASHI, J . Chem. SOC. Japan, 64, 1363 (1943); 66, 582 (1914) [Chem. Abstr., 41, 3774 (1947)]; T l E E B A Y A S H I &ID YARfADA, J. Chem. 8 O C . Japan, 66, 51 (1946) [Chem. Abstr., 43, 7924 (1949).

(32) Cf. KOVACS, J . Org. Chem., 16, 15 (1950). (33) Bart XIV, MULLER, ~ S ~ S Z A R O S , K6RmmnY, AND PCUCSMAN, J. Org. Chem., 17, 787

(34) MARIOS, Can. J. Research, [B] 16, 213 (1938). (1952).