[COXTRIBUTION FROM THE CHEMICAL
LABORATORY OF STANFORD UNIVERSITY]
THE USE OF THE FUSED EUTECTIC OF SODIUM AMIDE AND POTASSIUM AMIDE IN ORGANIC SYNTHESES F. W. BERGSTROM', H. G. STURZ,
AND
H. W. TRACY
Received December 3, 1946
According to Sachs (l),1-naphthylarnine is formed in good yield by heating naphthalene and phenol with sodium amide at temperatures above the melting point of the latter; the phenol is reduced to benzene in the process. Germuth (2), in a short note without experimental detail, claims that pure l-naphthylamine may be prepared by heating naphthalene and sodium amide in the absence of phenol. The well known reaction of Chichibabin, in which a-amino derivatives of pyridine, quinoline, and isoquinoline are obtained by the action of sodium amide upon the heterocyclic base in heated xylene or other inert solvent, has been reviewed elsewhere (3, 4). An important modification, suggested by Ostromislenski (5) and later adopted by Leffler (4)consists in the use of dimethylaniline instead of a hydrocarbon, in which both the sodium amide and the sodium salt of the reaction product are generally insoluble. It was thought that difficulties could be partly avoided by the use of the fused eutectic of sodium amide and potassium amide, which contains 33 mole per cent of the latter and melts at about 92" (6). It was also believed that primary amines might prove to be better media for these reactions than a tertiary amine, such as dmethylaniline, whose effectiveness is thought by Leffler (4)to be partly due to its ability to dissolve appreciable amounts of sodium amide at high temperatures. Attempts were first made to find an easily reducible organic or inorganic compound that would take the place of the phenol in the reaction of Sachs (l),or of the potassium nitrate in the equation below (7). CgHTN
+ 2KXH2 + KNOI
+
4C9HeN.NHK KNOz (in liquid ammonia at 20')
+ KOH + NH,
(I)
It was found that the yield of 2-aminoquinoline obtained in the reaction between quinoline and the fused amide eutectic in boiling xylene was poor and could not be sensibly improved by the addition of any one of the following substances: sodium nitrate, potassium nitrate, sodium azide, phenol, nitrobenzene (caution: nitrobenzene and sodium amide explode if heated to too high a temperature), benzalaniliine, or acetamide. Mercury did not improve the yield of l-aminoisoquinoline under similar conditions. I-Aminoisoquinoline was obtained in 69% yield by refluxing a xylene solution of isoquinoline with the fused amide eutectic; Chichibabin and Oparina (8) report a 38% yield with the use of sodium amide alone. Fairly good yields of a-alkylaminopyridines and a-alkylaminoquinolines were obtained by heating pyridine or quinoline with the fused amide eutwtic in a primary alkylamine; no aminopyridine or aminoquinoline mas isolated. The following compounds have been 1
Deceased, %far,29,1946. Proof not corrected by authors. 239
240
BERGSTROM, STURZ, AND T R S C P
prepared in this manner: 2-methylaminopyridine, 2-methylaminoquinoline, 2-n-butylaminopyridine, 2-n-butylaminoquinoline (in an impure state), 2-cyclohexylaminopyridine, 2-cyclohexylaminoquinoline,and 2-n-heptylaminopyridine. Potassium nitrate was generally unnecessary, though it appeared to be helpful in some cases. A typical reaction, representing the formation of 2-cyclohexylaminoquinoline, is shown in i;he following equation. CsH,N
+ MNHz + CsHiiKH2 + C&&N.N(M)CP,H~I+ Hz + NH3
(11)
When hydrolyzed, C9H6N-N(M)C6Hn 4- HzO + CgH6N.~HC6Hi1 NaOH MNH2 represents the amide eutectic. Attempts to prepare alkylmino pyridines and quinolines by heating a solution of a primary amine and pyridine or quinoline in xylene with the eutectic mixture of amides failed in one case, but succeeded in another, where a moderate yield of 2-n-heptylaminopyridinewas isolated. It is interesting to find that isoquinoline and the fused amide eutectic reacted in boiling cyclohexylamine to give l-aminoisoquinoline in 57% yield, apparently without the formation of l-cyclohexylaminoisoquinoline. Under similar conditions, acridine was converted to a tar. In the comparatively small scale experiments described in this article, pyridine and quinoline reacted with the fused amide eutectic in secondary amines only to give 2-aminopyridine (possibly with some 2,6-diaminopyridine) and 2-aminoquinoline. Attempts to make 2-anilinoquinoline by heating quinoline and aniline with the amide eutectic were unsuccessful. Chichibabin and Seide (9) were able to prepare 2-anilinopyridine in poor yield by heating sodium anilide with pyridine. TEIE REACTION MECHANISM
Bradley and Robinson (10) warmed a mixture of nitrobenzene, piperidine, and sodium amide, thereby obtaining a 27% yield of 4-N-piperidinonitroben~ene~ in accordance with the equation,
+
+
+
+
C6HSN02 CsHloNH NaNHz + C6HION.CeH4N02 NH3 (NaH) (111) An electronic interpretation is given, based on the assumption that sodium-Npiperidide, CsHloNNa,is forrned as an intermediate. The highly active anion of this compound attacks the nitrobenzene molecule in the para position, at a point that can become positively charged because of the (- ) electromeric effect of the nitro group. Bergstrom, Granara, and Erickson (11) have similarly prepared p-nitrotriphenylamine by the action of sodium diphenylamide on nitrobenzene. According to the mechanism of Bradley and Robinson, the formation of sodium cyclohexylaminoquinoline should follow the equations, NaNHz C6H11NH2 + C6HllNHNa NH3 (IV, a> C6HllNHNa CgH7N C9H8N.NNaC6H114- Hz (IV, b) However, when cyclohexylamine was refluxed with the amide eutectic, very little ammonia was formed, indicating lack of appreciable reaction, an equilibrium
+
+
+
--.f
SYNTHESES WITH SODIUM-POTASSIUM AMIDES
24 1
with very little sodium cyclohexylamide present, or, less probably, the formation of a salt, CsHI1NHNa.NH3,with ammonia of crystallization. The equilibrium of (IV, a) should be gradually displaced toward the right if ammonia is lost during the refluxing. In view of these facts, it is worth while to suggest an alternate mechanism, in which the amide ion first attacks the carbimide group (-CH=N-) of quinoline to form (A), equation (V); this is of course equivalent to an addition compound of quinoline with potassium amide. The amino group is then exchanged for -NHR in a reaction that is doubtless favored by an excess of the primary alkylamine; reasons why this is a logical step are discussed in a previous article (12).
+ CH(NH+N(A) + RNHz + CH(NHR)N- + NHs
CH=N CH(NH2)N-
"2-
(VI
The formation of a 2-alkyl-quinoline or -pyridine then will be expressed by the following over-all equation, CH(NHR)-N-
C(NMR)=N
+
--M+
C(NMR)=N HzO --+ C(NHR)=N where M=Na or K +
+ Hz + MOH
(VI)
The mechanism whereby this is accomplished is not yet clear in all of its aspects; a tentative suggestion for a related liquid ammonia reaction has been made in a previous paper (13). EXPERIMENTAL PART
Sodium amide-potassium amide eutectic was prepared by bubbling ammonia gas through
a mixture of 77 g. (3.4atoms) of sodium and 64.5 g. (1.6 atoms) of potassium a t 350",in accordance with directions given in Organic Syntheses (14). The mixture was cooled toward the end to about 'BO", and ammonia gas passed through for about half an hour to diminish the amount of hydride; thereafter, the inlet cube was raised above the level of the melt and the latter allowed to cool to room temperature in a slow stream of ammonia. Pouring of the molten amide on a metallic pan, as suggested in previous directions (14),will result in a bad fire. When cool, the nickel crucible containing the amides was inverted on a metal plate and tapped to dislodge the solid, which was broken up and stored in a wide-mouth bottle filled with ammonia gas (the ground stopper must fit tightly and be greased near the top). After each removal of amide, the bottle was again filled with ammonia and stoppered. The average "molecular weight" of this mixture, or, more precisely, the weight containing 16 g. of amide ion, is calculated to be 45. All reagents were of high purity and were dried before use either by desiccation or, if a liquid, by fractional distillation. The melting points are uncorrected. I-Aminoisoquinoline. Fifteen grams of the amide eutectic was well ground in a mortar under 200 cc. of xylene, and then transferred, along with the xylene, to 500-cc. threenecked round-bottomed flask. The mixture was heated a t 100' on a boiling water-bath and mechanically stirred while 10 g. of isoquinoline was slowly added from a dropping-funnel. After heating and stirring for an additional two hours, the flask was cooled and the xylene decanted as well as possible. The excess of amide was destroyea by passing over it a current of moist air, obtained by passing air through two wash bottles of water maintained a t a temperature of 60-70'.
242
BERGSTROM, STURZ, AND TRACY
The hydrolyzed residue was crystallized from hot water; a dark colored oil separating a t this stage was largely 1-aminoisoquinoline, which could be dissolved by adding more hot water. I n four experiments, the yield of 1-aminoisoquinoline varied between 63.5 and 69.7%, while in one run a 760/, yield of hydrogen was obtained. With 6 g. of the eutectic and 10 g. of isoquinoline in 200 cc. of xylene a t looo, the following yields of l-aminoisoquinoline were recorded; with 10 minutes heating, 23%; with 2 hrs. heating, 41%. When 26 g. of isoquinoline and 15 g. of the eutectic were heated for 2 hrs. in 200 cc. of xylene at loo", the yield of 1-aminoisoquinoline dropped to 37%, showing that i t is better t o operate i n the more dilute solutions. Twenty grams of the amide eutectic and 100 cc. of dry cyclohexylamine were heated with 5.5 g. of isoquinoline and 5 g. of potassium nitrate for 1.5 hours at 135". After careful hydrolysis the upper amine layer was separated and steam distilled t o remove the amine; 3.5 g. or 57976 of 1-aminoisoquinoline, m.p. 122-123', separated from the steam non-volatile liquid on cooling. d-Aminopyridine. Ten grams of the amide eutectic, 3 cc. (2.95 9.) of pyridine, and 50 cc. of diethylamine were heated in a small autoclave for two hours a t 120". After cooling, water (30 cc.) was slowly added t o the contents of the bomb, and the aqueous layer extracted several times with benzene. Distillation of these extracts, first at atmospheric pressure t o remove benzene and diethylamine, and then in vacuo gave 1.6 g. of 2-aminopyridine (46y0), m.p. 50-52', b.p. 91-93" a t 8 mm. One-half gram of a substance, probably 2,6diaminopyridine, was obtained at 144' and 6 mm. When crystallized from benzene the melting point became 121-122"; according to Chichibabin and Seide (9), the melting point of 2,6-diaminopyridine is 122". Pyridine (16 g.), the amide eutectic (10 g.), and xylene (30 cc.) were heated for seven hours at 140-150' (oil-bath temperature). After cooling, 20 cc. of saturated sodium carbonate solution was cautiously added to hydrolyze the excess of amide. The xylene layer was separated and combined later with two benzene extracts of the aqueous solution, and then distilled as described in the paragraph above t o give 7.2 g. (38%) of 2-aminopyridine; better yields have been reported with the use of sodium amide alone (9). X o increase in yield was obtained in dibutylamine as a solvent, though the reaction time appeared t o be decreased. 8-Aminoquinoline. The yield of 2-aminoquinoline obtained by heating quinoline with an excess of the amide eutectic i n xylene a t 100" for six hours was inferior t o that reported by Chichibabin and Zatzepina (15), who used sodium amide alone. The replacement of the xylene by diethylamine or by dibutylamine offered no advantages. Alkylamino Pyridines and Alkylamino Quinolines Procedure A . 8-Cyclohexylantinoquinoline. Twenty grams (0.45 mole) of the sodium amide-potassium amide eutectic was well ground under benzene and transferred to a 500cc. reaction flask with standard taper ground glass joints (A of Fig. 1). The benzene was decanted as well as possible and replaced by 100 cc. of cyclohexylamine which had been dried over sodium ribbon and fractionated. Five grams (0.05 mole) of dry and powdered potassium nitrate was added to the mixture. The levelling bulb, H, was lowered to the level of the mercury seal, I, and the reactants heated at 100-llOo (oil-bath temperature) for thirty minutes, or until no more air was expelled into the nitrometer, F. Air in the latter was then displaced by raising H and opening the stopcock, G. With the latter closed, H was again lowered to the level of the mercury surface in I, and 5.5 g. of quinoline (0.043 mole) added dropwise from the burette, B, over a period of about half an hour, with stirring. (The stirrer passed through a packed gland.) B fairly vigorous reaction took place with the evolution of hydrogen; a total of 740 cc. (0.0330 mole) of gas, calculated t o standard conditions, was obtained, a yield of 77%. The mixture was stirred and heated for about 15 minutes after the gas evolution had ceased. The flask, A, was now disconnected from the nitrometer, cooled, and the contents hydrolyzed by the slow addition of water, a total of about 500 cc. being used in order t o dissolve the bulk of the cyclohexylamine. The floccu-
SYNTHESES WITH SODIUM-POTASSIUM AMIDES
243
lent gray solid that separated was filtered and crystallized from 200 cc. of 50% ethanol to give 5.7 g. (59%) of white needles melting a t 125-126". Anal. Calc'd for ClsHleN*:C, 79.62; H, 8.02. Found: C, 79.36; H, 8.27. A repetition of this experiment with the omission of the potassium nitrate, and one hour heating gave 5.4 g. (56%) of 2-cyclohexylaminoquinolinemelting a t 124-125', but the yield
G
E
02
C
D
FIG. 1
occasionally dropped practically to zero. More consistent results were obtained when potassium nitrate waa used. 2-Cyclohexylaminoquinoline was also prepared by heating 2-chloroquinoline (4.1 g.) with cyclohexylamine (15 cc.) for six hours a t 200' in a sealed tube, with the addition of one gram of copper powder. The cooled reaction product was poured into water and the resulting precipitate crystallized from 50% ethanol as above. The yield was 3.3 g., or 58%. The melting point and the mixed melting points with material prepared by the action of the eutectic on quinoline in cyclohexylamine were 125-126'. 2-Cyclohexylaminopyridine. In accordance with the procedure outlined above, 20 g. of
244
BERGSTROM, STURZ, AND TRACY
the eutectic, 5 g. of potassium nitrate, 5.9 g. of pyridine, and 100 cc. of cyclohexylamine reacted at 100-120" for one hour. There was obtained 4.5 g., or 34%, of cyclohexylaminopyridine melting at 123-124' and 1,230 cc. of gas, calculated to standard conditions (74%). The isolation followed the scheme given above for cyclohexylaminoquinoline; the precipitate was crystallized several times from dilute alcohol. Anal. Calc'd for CllHlsNz: C, 74.96; H, 9.15; N, 15.90. Found: C, 74.92; H, 9.35; N, 16.12. 2-Bromopyridine (2.7 9.) was heated with cyclohexylamine (4.5 9.) at 180' for five hours in a sealed glass tube. Water was added t o the reaction mixture and the resulting precipitate filtered and washed with small quantities of the same solvent t o remove cyclohexylammonium bromide. The yield of 2-cyclohexylaminopyridinemelting at 123-124' was 1.2 g., or 40%. The melting points of three mixtures of this with the material prepared by the first method were the same. 2-n-Butylaminoquinoline. Procedure (A) was followed, with the use of 100 cc. of nbutylamine, 20 g. of the eutectic, 5 g. of potassium nitrate, and 5.5 g. of quinoline. There was collected 1120 cc. of gas under standard conditions in place of a theoretical 950 cc. The supernatant oily layer left after the hydrolysis with a small volume of water was dried over potassium hydroxide and distilled, first to remove butylamine, and then at 145-170" and 4 mm. to obtain crude 2-n-butylaminoquinoline. The yield was about 40% of the theoretical. A picrate, crystallized several times from methyl isobutyl ketone, melted a t 2015-202.5". Anal. Calc'd for C1gH1DNa07: C, 53.15; H, 4.46; N, 16.31. Found: C, 53.43; H, 4.84; N, 16.13. A much better method of prepitration is the following : Four grams of 2-chloroquinoline, 25 cc. of n-butylamine, and 0.2 g. of copper powder were heated in a sealed glass tube at 170" for five hours. Isolation of the product in accordance with the above directions, gave 3.8 g. of a yellowish liquid boiling at 168-170" a t 4 mm., a 78% yield. The picrate recrystallized from methyl isobutyl ketone, melted at 199-200', and at 200-201' when mixed with the picrate whose analysis is given above. It is possible that some isomerization of the free base occurred during distillation. 2-n-Butylaminopyridine. I n accordance with procedure (A), 5.9 g. of pyridine and 130 cc. of n-butylamine were heated for one and one-half hours with 5 g. of potassium nitrate and 20 g. of the amide eutectic. The initial temperature was l l O o , finally rising t o about 125" at the end of the reaction. .4 small amount (50 cc.) of water was added to the cooled mixture to hydrolyze the excess of amide. The butylamine layer was separated, dried over potassium hydroxide, and distilled to yield unchanged amine, and then 2-n-butylaminopyridine a t 125" and 14 mm. The yield of material melting at 42" was 7.2 g. or 64%. The picrate melted a t 135.5", in fair agreement with the value of Slotta and Franke (16), 138', who give 45" as the melting point of the free base. I n a repetition of this experiment with omission of the potassium nitrate, 1,600 cc. of gas (under standard conditions) was collected, as compared with a theoretical of 1,680 cc. The yield of butylaminopyridine was 60y0. If sodium amide alone was used, the reaction time was trebled, but the amount of gas collected was very close t o the theoretical. The yield of butylaminopyridine in this case was 570j0. The yield dropped t o 50% when equivalent molar quantities of the amide eutectic and pyridine were used. Procedure B. I-n-Heptylaminopyridine. h mixture of 23 g. of n-heptylamine, 5.5 g. of the sodium amide potassium amide eutectic, 3.95 g. of pyridine, and 50 cc. of xylene was heated under reflux (at about 140') for three hours, with mechanical stirring. The excess of amide was cautiously decomposed with water and the water layer extracted once with benzene. The combined benzene and xylene solutions were extracted with 180 cc. of dilute acetic acid to remove pyridine and then with 12y0hydrochloric acid to remove heptylaminopyridine, which was subsequently precipitated by the addition of excess sodium carbonate. The oil was extracted with ether, the latter evaporated, and the residue crystallized from low-boiling ligroin. The yield of white needles was 2.0 g. or 21%; the melting point was 45.5-46.0'.
SYSTHESES WITH SODIUM-POTASSIUM AMIDES
245
Anal. Calcd for C,QHzoNz: C, 74.96; H, 10.48; W, 14.57. Found: C, 75.36; H, 10.37; E,14.2!3. An attempt to prepare 2-cyclohexylaminc~quinoline by this method was unsuccessful. Procedure C. 8-Methylaminoquinoline. Twenty-eight grams of the amide eutectic (0.62 mole), 25.7 g. (0.199 mole) of quinoline, and 22.7 g. (0.224 mole) of potassium nitrate were placed in an autoclave (17) into which 97 g. of anhydrous methylamine was distilled. The reactants were heated for four hours a t 100-135", allowed to cool during about two hours to 70°, and finally cooled to room temperatures by immersion in water. The methylamine was distilled into a small supply tank, held at OD, through a connecting lead tube, and the solid remaining hydrolyzed by adding benzene, followed by a small amount of water. The thick liquid left after evaporating the benzene was extracted repeatedly with boiling ligroin (b.p. 55-85'). When each extract had reached a temperature of about 30°, a sticky oil had deposited; the supernatant liquid was decttnted, cooled further to O", and stirred, whereupon white crystals separated. The melting point varied between 68" and 81", since there are two crystalline modifications of 2-methylaminoquinoline melting at 71" and a t 81-82' (18). The complete separation of the crystals from the sticky impurity was very tedious. The yield was 8.1 g. or 267,. Calc'd for CloHlohi2: C, 75.92; H, 6.37; N, 17.71. Anal. (m.p. 79-82'). Found: C, 75.96; 75.97; H, 6.36, 6.30; N, 17.70, 17.80. I n a repetition of this experiment on a smaller scale, the methylaminoquinoline was distilled at 6 mm. and 158", but did not solidify when cool; i t was converted to a picrate of about the right melting point (230-233'; correct, 234-236'). A second (full scale) repetition with a longer period of heating (5.5 hours a t 105" with approximately 5 hours consumed in heating and in cooling the autoclave) gave a benzene extract from which brownish crystals separated on concentration. When recrystallized from benzene (the hot solution was filtered), there was obtained 3.36 g. of crude material melting at 12C-125", and a t 127-128" after several recrystallizations from the same solvent. Anal. Calc'd for C ~ O H I ZC, N ~74.96; : H, 7.55; N, 17.49. Found: C, 74.93,74.95; H, 7.44,7.53; N, 17.49,17.61. A mixed melting point determination showed that this could not be 2-aminoquinoline; i t may be a monomeric or polymeric dihydromethylaminoquinoline, or perhaps 3-methyl2-methylaminoindole, even though a pine splinter reaction was negative. R-Methylaminopyridine. 2-h!Iethylaminopyridine, b.p. 100-102' at 18 mm. or 85-88' at 4 im. was prepared in 2.9 g. (73%) yield by heating pyridine (2.95 g.), methylamine (about 20 g.), potassium amide (14 g.), and potassium nitrate (2.5 g.) for one and one-half hours at 90" in a small glass lined tube ail1,oclave. The methylamine was evaporated and the solid hydrolyzed with a mixture of benzene and a little ice-water; the benzene layer was distilled in the usual manner. The picrate melted at 188-192', and at 193-194" after several crystallizations from methyl isobutyl ketone. Chichibabin (19) reports that the picrate melts at 190", and the free base boils a t 90" Itt 9 mm. Almost identical results were obtained with the use of the amide eutectic. SUMMARY
1. The eutectic of sodium amide and potassium amide, which melts at about 92" ( 6 ) , is occasionally a better reagent than sodium amide in organic syntheses since reactions may be carried out with the fused material at moderate temperatures, thereby avoiding surface effects. The yield of l-aminoisoquinoline has been improved to about 70%, but no advantage was found in the use of the eutectic to prepare aminopyridine or aminoquinoline. 2. 2-Alkylaminopyridines and 2-alkylaminoquinolines are obtained in fairly good yields by heating the eutectic mixture of sodium amide and potassium amide with pyridine or quinoline dissolved in a primary aliphatic amine. The following compounds have been prepared in this manner: 2-methylaminopyridine,
246
BERGSTROM, STUFZ, AND TRACY
2-n-butylaminopyridine, 2-n-heptylaminopyridine, 2-cyclohexylaminopyridine, 2-methylaminoquinoline, 2-butylamirzoquinoline (in a crude state), and 2-cyclohexylaminoquinoline. 1-Aminoisoquinoline appears to be the only product formed when isoquinoline and the amide eutectic are heated in cyclohexylamine. The theoretical aspects of the reaction are discussed. 3. 2-Aminopyridine (and possibly also 2,6-diaminopyridine) are formedwhen pyridine is heated with the amide eutectic in either diethylamine or in dibutylamine; dialkylaminopyridines have not been isolated. STANFORD UNIVERSITY, CALIF. REFERENCES
(1) SACHS,Ber., 39, 3023 (1906). J . Am. Chem. SOC..61,1556 (1929). (2) GERMUTH, AND FERNELIUS, Chem. Revs., 12,154 ff. (1933);20,463 ff. (1937). (3) BERGSTROM (4) LEFFLER,Chapter 4 of volume I of ‘LOrganicReactions,” Roger Adams, editor, John Wiley and Sons, New York, 1942, p. 91 ff. (5) OSTROMISLENSKI, J . Am. Chem. SOC.,66, 1713 (1934). 46,712 (1923). (6) KRAUSAND CUY,J . Am. Chem. SOC., J. Org. Chem., 2,414 (1937). (7) BERGSTROM, (8) CHICHIBABIN AND OPARINA, J . Russ. Phys.-Chem. SOC.,60, 543 (1920);Chem. Abstr., 18, 1502 (1924). (9) CHICHIBABIN AND SEIDE,J. l2uss. Phys.-Chem. Soc., 46, 1216 (1914); Chem. Abstr., 9, 1901 (1915). (10) BRADLEY AND ROBINSON, J . Chem. SOL,1254 (1932). (11) BERGSTROM, GRANARA, AND E:RICKSON,J . Org. Chem., 7,98 (1942). (12) BERGSTROM, Chem. Revs., 36, 114 (1944). J . Org. Chem., 2,415 (1937);Ann., 616,35 (1934). (13) BERGSTROM, “Organic Syntheses,” John Wiley and Sons, X’ew York City, 1940, vol. (14) BERGSTROM, 20, p. 86. (15) CHICHIBABIN AND ZATZEPINA, J . Russ. Phys.-Chem. SOC.,60,553 (1920);Chem. Abstr., 18, 1502 (1924). (16) SLOTTA AND FRANKE, Ber., 63,690 (1930). J . Org. Chem., 2, 424 (1937). (17) BERGSTROM, (18) SYNERHOLM AND BERGSTROM, unpublished observations. (19) CHICHIBABIN, KONOVALOVA, AND KONOVALOVA, J . Russ. Phys.-Chem. SOC.,63, 193 (1921); Chem. Zentrl., 1923, 111, 1023; Ber., 64, 817 (1921); CHICHIBABIN AND KNUNYANZ, Ber., 61, 2216 (1928).
