Energy & Fuels 1989, 3, 357-361
357
Studies on the Decomposition of Ethyl Diazoacetate and Its Reaction with Coal. Formation of a New Tetrameric Product and Reagent Access within the Coal Martin Pomerantz* and Peter Rooney Center for Fossil Fuels Chemistry, Department of Chemistry, The University of Texas a t Arlington, Arlington, Texas 76019-0065 Received November 9, 1988. Revised Manuscript Received February 13, 1989
A new tetrameric pyrazoline, 10, has been observed in the thermal and Fez03-catalyzed decomposition of ethyl diazoacetate (2) as well as when several coal samples were treated thermally with 2 under various conditions. Identification of 10 was based on spectral properties and an independent synthesis. A comparison of the amounts of diethyl fumarate (3), diethyl maleate (4), the trimeric pyrazoline 5, triethyl trans-cyclopropane-l,2,3-tricarboxylate(S), and the tetrameric pyrazoline 10 formed in the coal reactions with the relative quantities produced in the thermal and Fe203-catalyzed reactions of 2, both neat and diluted with p-xylene, showed that there were several successive and competing reactions occurring, one of which was independent of the concentration of 2. Further, on the basis of the observation that the product distribution of 3-5,8, and 10 in the Fe203-catalyzed decomposition of 2 in relatively dilute solution is similar to that observed in the coal reactions, with cyclopropane 8 being the major product in both cases, and that 2 is reacting mainly with the coal, it is concluded that 2 is fairly well dispersed within the coal. In addition, it is clear that swelling of the coal with dioxane did very little to facilitate access of 2 into the coal. Instead the dioxane merely acted to allow for more complete extraction of the products after 2 had reacted with the coal, presumably by keeping the matrix structure more open, than when the dioxane was not used. Introduction We recently described the reaction of (ethoxycarbony1)carbene (l),formed by the thermal decomposition of ethyl diazoacetate (2; eq 11, with an Illinois No. 6 N2CHCOzEt a* CHCO2Et N2 (1) 2 1 HVCB coal.' We also examined the effect of mineral catalysts on this decomposition and the implications this had for the coal reactionsa2 Further, we have demonstrated, contrary to what is generally believed, that (ethoxycarbony1)carbene (1) can be quite selective in its reaction with organic molecule^.^ Thus, the reaction of thermally produced 1 with 23 aromatic, fused aromatic, heteroaromatic, and benzo-fused aromatic compounds (many of these ring systems are known to be present in coal) displayed selectivities for 1 of up to 150-fold relative to a simple benzene derivative, toluene. These results along with TGA and extraction results' coupled with the studies presented in this paper whereby relatively small amounts of byproducts of 2 are observed when 2 reacts with coal, indicate that 2 may be quite useful as a probe to study the molecular structure of coal. The TGA analysis, for example, indicated that at temperatures as low as 250 "C there is considerably more volatile material formed than with untreated coal.' The untreated coal, by comparison, showed reasonable volatility at about 450 O C , but even at this temperature there was much less volatile material produced than with the treated coal.' In order to determine if the major reaction of 1 and 2 was with the coal rather than with themselves, it was required that we first prepare the known trimer products formed when 1 and 2 react with the dimers of 1, namely diethyl fumarate (3) and diethyl maleate (4). Esters 3 and 4 are known to undergo 1,3-dipolar additions with 2 to
+
(1) Pomerantz, M.; Rooney, P. Energy Fuels 1987,1,401. (2) Pomerantz, M.; Rooney, P.; Cardona, R. Fuel 1988, 67, 1096. (3) Pomerantz, M.; Rooney, P. J. Org. Chem. 1988, 53, 4374.
0887-0624/89/2503-0357$01.50/0
form the trans-pyrazoline 5.44 The observation that the sterically favored' trans-pyrazoline 5 is formed exclusively is consistent with a concerted 1,3-dipolar cycloadditions in which the diazo molecule, 2, approaches 3 or 4 so that the less hindered adducts 6 and 7, with the ethoxycarbonyl groups on the newly formed a-bond trans oriented, are formed (Scheme I).6 Of course subsequent tautomerism removes the inherent stereochemical difference between 6 and 7 and provides only the more stable trans-2pyrazoline 5. Further, pyrazoline 5 is known to decompose to cyclopropane 8 (via loss of nitrogen from the 1EtOQC CO, Et &H I
Et02C
H
I H
8 pyrazolines, 6 or 7)9when heated above 180 OC or under catalytic conditions a t lower temperatures.*+ Capillary gas chromatographic analysis of the coal extracts showed only small amounts of 3-5 and 8 to be present.' Further, another potential trimer of 1, reported once as a byproduct in the CuC12-catalyzed reaction of (4) For reviews, see: (a) Kirmse, W. Carbene Chemistry, 2nd ed.; Academic: New York, 1971. (b) Marchand, A. P.; MacBrockway, N. Chem. Reo. 1974, 74,431. (c) Dave, V.; Warnhoff, E. Org. React. 1970, 18, 217. (5) Wulfman, D. S.; Peace, B. W.; McDaniel, R. S., Jr. Tetrahedron 1976,32, 1251. B 1971, 646. (6) Forbes, A. D.; Wood, J. J. Chem. SOC. C 1969, (7) Andrew, S. D.; Day, A. C.; McDonald, A. N. J.Chem. SOC. 787. (8) For review, see: Cowell, G. W.; Ledwith, A. Q. Reu. Chem. SOC. 1970, 24, 119. (9) For example, see: (a) Behr, L. C.; Fusco, R.; Jarboe, C. H. In Pyrazoles, F'yrazolines,F'yrazolidines,Zndazoles and Condensed Rings, Wiley, R. H., Ed.; Interscience: New York, 1967; Chapter 8. (b) Jacobs, T. L. In Heterocyclic Compounds; Elderfield, R. C., Ed.; Wiley: New York, 1957; Chapter 2. (c) Jones, W. M. J. Am. Chem. SOC.1960,82,3136. (d) Jones, W. M. Zbid. 1969,81, 5153. (e) Jones, W. M. Zbid. 1968,80, 6687.
0 1989 American Chemical Society
Pomerantz and Rooney
358 Energy & Fuels, Vol. 3, No. 3, 1989 Scheme I
1
6
1
4
7
alcohols with 2, namely the triethyl ester of aconitic acid (9),l0was not observed by GC analysis in the coal extracts.
of these tetramers, however, have ever been detected under thermal or catalytic conditions, and so this report is the first observation of a tetramer of 1 and 2 formed under these conditions.
9 Therefore, we concluded that the major reaction of 1 and 2 was with the coal.' We now wish to report that a new tetrameric byproduct from the thermal decomposition of 2, pyrazoline 10, has been isolated in the reaction of 2 with coal and is formed in fairly significant amounts. The formation of a different
Pyrazoline 10 was prepared by the reaction of 2 with 5 in the presence of CuCI. This was based on the method of Saegusa,lSin which it was shown that amines could be N-alkylated with diazomethane or with 2 in the presence of CuCl or CuCN. Isolation of this new compound by radial chromatography (see Experimental Section) gave a light green oil, which capillary gas chromatography showed to be >99% pure. Elemental analysis, FT-IR spectroscopy, and IH NMR spectroscopy and GC-MS were all consistent with structure 10. Analysis of the appropriate blocks of a 2-D 'H NMR COSY spectrum gave a three-bond coupling constant, 3 J ~of ~the , hydrogens attached to C-4 and C-5 (H4 and H5) of 10.6 Hz. This value, at first sight, appeared rather large when compared with the value of 5.4 Hz that we observed in 5 for the corresponding trans C-4 and C-5 hydrogens. (This compares with the literature value of 6.5 H Z . ) ~Although the three-bond coupling constants of the trans hydrogens on these positions of 2-pyrazolines are typically in the range of 3-10 Hz,16J7it is known that that substituents on nitrogen can have a rather significant effect on these coupling constants.16J8 For example when R on the nitrogen in compound 14 is varied from 2,5-dichlorophenylto phenyl
Results and Discussion
Et02C
FfCo2Et
Et02C X\N,N-CH2-COzEt
10 tetramer of 1, namely tetraethyl 1,2,3,4-cyclobutanetetracarboxylate (11) has been reported as a byproduct Et02C
\
COZ Et /
H
H
from the interaction of 2 with 6-methyl-5-hepten-2-onel1 H5C6 &c6H5 or ethyl 4-methyl-3-penten0ate'~in the presence of copper bronze. However, further studied3 revealed the actual product was dimer 3 rather than the tetramer 11. Finally, there is one report14 that the photolysis of methyl diazo14 acetate (NZCHCOzMe)results in the isolation of four to methyl, the trans coupling constant, 3 J Hvaries ~ , from tetramers whose NMR spectra are said to be consistent 5 to 8 to 9.5 Hz,ls while the corresponding cis coupling with structures 12 and 13, for all four compounds. None constant, which in 2-pyrazolines is known to be larger than the trans coupling constant, varies from 10 to 12 to 14 Hz, respectively.16 Additionally, since the starting 2-pyrazoline 5 is well known (ref 4 and references cited therein) to have the trans configuration a t C-4 and C-5, as mentioned above, it is expected that 10 will maintain this stereo12 13 chemistry and thus the large value of 3 J must ~ ~be the (10)Saegusa, T.;Ito, Y.; Kobayashi, S.; Hirota, K.; Shimizu, T. J.Org. Chem. 1968,33,544. (11)Owen, J.; Simonsen, J. L. J. Chem. SOC.1932,1424. (12)Owen, J.; Simonsen, J. L. J. Chem. SOC.1933,1225. (13)Reid, E.B.; Sack, M. J. Am. Chem. SOC.1961,73, 1985. Ritter, A. Tetrahedron Lett. 1968,3189. (14)Schenck, G.0.;
(15)Saegusa, T.; Yoshihiko, I.; Kobayashi, S.; Hirota, K.; Shimizu, T. Tetrahedron Lett. 1966,6131. (16)Hassner, A,; Michelson, M. J. J. Org. Chem. 1962,27,3974. (17)Brey, W.S. Jr.; Valencia, C. M. Can. J. Chem. 1968,46, 810. (18)Elguero, J.; Marzin, C. Bull. SOC.Chim. Fr. 1970,3466.
Decomposition of Ethyl Diazoacetate
Energy & Fuels, Vol. 3, No. 3, 1989 359
Table I. Percent of 3-5,8, and 10 Observed in Coal Extractsa compd coal Ab#' coal Bb coal Cb 3 0 (0.43) trace trace 4 0 (trace) trace trace 5 1.1 (2.3) 2.1 5.5 8 10
11.3 (8.2) 4.0 (3.8)
12.8 4.4
9.4 3.9
tot. % extractedd
26 (37)
37
35
'Percent of total extractable material. For a description of the different coal samples, see text. 'The numbers in parentheses are the result of further extraction with dioxane; see text. Based on the weight of coal before and after Soxhlet extraction.
result of a simple substituent effect. Next, the amount of 3-5, 8,and 10 formed when an Illinois No. 6 HVCB coal (described previously)' was treated with an equal weight of 2, under various conditions, was determined (Table I). For one sample, called coal A, the coal, 2, and pentane were stirred overnight and the pentane was removed under reduced pressure. For a second sample, called coal B, the coal was f i t swelled with dioxanelg and then dried. It was then mixed with 2 and pentane and stirred overnight, and the pentane was removed under reduced pressure. Finally, for a third sample, called coal C, the dioxane-swollen coal and 2 were stirred overnight, without solvent. In each of these cases the ethyl diazoacetate (2) was then decomposed by heating the coal/2 samples slowly to 130 OC. With all three samples, the evolution of nitrogen was vigorous at approximately 70 OC, as was reported earlier for the reaction of 2 with The treated coal samples were then extracted in a Soxhlet extractor with toluene-methanol (9:l). The amount of 3-5,8,and 10 was determined quantitatively by GC using authentic samples. As noted earlier, compound 9 was not detected by GC in any of the coal extracts. The results are presented in Table I. When the dioxane-preswelled samples, coals B and C, were Soxhlet extracted, more extractable material was obtained than when dioxane was not used (coal A). One explanation is that this difference was due to swelling of the coal by d i o ~ a n e , 'which ~ would allow for better penetration of 2 into the coal m a t r i ~ . ' ~ However, .~ if this were true, much more of the byproducts 3-5,8, and 10 should have been observed in coal A than were actually detected, since simple surface reaction of small droplets of 2 on the coal would result in very extensive reaction of 1and 2 with themselves and each other. When coal A, which had been extracted with the toluene-methanol mixture, was subjected to an additional extraction with dioxane (12 h) the total extractable material of coal A increased to 37%, with the total (from both extractions) percent of 3-5,8,and 10 observed as 0.43, trace, 2.3, 8.2, and 3.8, respectively, comparable with the results obtained for preswelled coals B and C. From these results, it is clear that dioxane does little to facilitate access of 2 into the coal. Instead, the dioxane acts to distort the structure of coals B and C, and after reaction with ethyl diazoacetate (2), this more open structure is maintained and allows for more of the reaction products to be e x t r a ~ t e d . ' ~ ~In ~ ' coal A, which was not dioxane swelled, considerably less material was extracted. However, the remaining products were extracted with an additional extraction using dioxane. Control experiments
Table 11. Relative Amounts of 3-5,8, and 10 Produced from the Decomposition of 2 Thermally and Catalyticall9 compd 3
2 neat
'C.
+ Fe20, neat
2.7 1.1
4
5 8 10
2 diluteb 2
3.0
8.7
0.69
1.0
1.0
1.0
2+ &Os diluteb 2.5 1.1 2.6 13.6 1.0
'In each case, 2 was decomposed by slowly heating to 180-135 10% w/v of 2 in p-xylene.
showed that for coals B and C after toluene-methanol extraction nothing more could be extracted with an additional dioxane extraction. Several points concerning the amounts of products 3-5, 8,and 10 should be discussed. First, and most important, the total amounts of compounds 3-5, 8, and 10 in the extracts of coals A-C were only 16-19% of the total coal extracts (15% of total extracts when coal A was further extracted with dioxane). The treated coal samples showed a 50% increase of extractable material (about 30-35% when the amounts of 3-5, 8,and 10 were taken into account) relative to untreated coal, which showed 24% Soxhlet-extractable material. In addition, preliminary GC-MS analyses of the extracts of the treated coal indicate that much of the treated coal extracts are able to elute through a gas chromatograph and that the vast majority of these elutable products contain ester groups attributable to the incorporation of 1 into the coal fragments. While the reason for the enhanced extractability of the ethyl diazoacetate treated coal and whether this involves depolymerization of the coal or greater extractability of trapped species due to the attachment of ester groups cannot be established with certainty until the extracts can be identified more fully, it is clear that the major reaction of 2 is with the coal. It is also interesting to note that since cyclopropane 8 does not form pyrazoline 5 a t the low temperatures used here, its formation must have been the result of a catalyzed reaction (vide Further, products 8 and 10 were the result of two competing reactions of pyrazoline 5, both of which were most likely catalyzed, but only of which (5 10) required additional diazo compound 2 or carbene 1. The observations of trimers and particularly tetramer 10 suggest there are regions of relatively high concentrations of 2 (and l),which seems to pose a paradox since we have also concluded that the majority of 1 and 2 react with the The observations described below, however, involving the catalytic decomposition of 2, indicate that these trimers and tetramers can form under relatively dilute conditions. It should also be mentioned that an attempt was made to treat the coal with 2 in dioxane and then remove the solvent. Unfortunately, 2 codistilled with the dioxane when a rotary evaporator (reduced pressure) was used. Attempts to fractionally distill 2 a t reduced pressure led to considerable decomposition of 2 during the distillation. To further explore this idea of possible regions of high and low concentration of 2 and what effect a catalyst such as Fe203(which may well be the active mineral catalyst in the coal) might have on these product distributions, the
-
(22) We reported, based on GPC studies, that little if any polymer of
2 was formed in the reactions of 2 with coal.' We have now reexamined
(19)Larsen, J. W.; Green, T. K.; Choudhury, P.; Kuemmerle, E. W. in Coal Structure, Gorbaty, M. L.; Ouchi, K.; Eds.; American Chemical Society: Washington, DC; 1981,Chapter 18. (20) Rincon, J. M.; Cruz, S. Fuel 1988,67,1162. (21)Brenner, D. Fuel 1983,62,1347.
the possibility of polymer formation and have used GPC with refractive index detection and low molecular weight poly(viny1acetate) as a model ester polymer and have confirmed that, to within our current detection limits (2%), no polymer forms in either the coal reaction with 2 or in the neat decomposition of 2 both with and without Fe203catalyst.
Pomerantz and Rooney
360 Energy & Fuels, Vol. 3, No. 3, 1989
ethyl diazoacetate (2) was decomposed thermally both neat and diluted to 10% w/v in p-xylene. In addition 2 was decomposed by using Fe203as the heterogeneous catalyst both neat and diluted to 10% w/v in p-xylene. Table I1 shows the results of these studies and gives the amounts of 3-5 and 8 relative to tetramer 10, which was set equal to 1.0. The data in Table I1 show that the dimers 3 and 4 were not detected when 2 was reacted neat both with and without catalyst. This, of course, is because they are quite reactive in the presence of high concentrations of ethyl diazoacetate (2) and result in the formation of pyrazoline 5. This, in turn, reacts with more 2 to provide tetramer 10. No cyclopropane 8 was observed when only neat 2 was heated since the temperature was not high enough to get tautomerism and nitrogen e x t r u ~ i o n .Since ~ ~ there was also no cyclopropane 8 formed from 2 and Fe203neat, we conclude that in the competing reactions of 5 to form 8 by nitrogen extrusion and 10 by reaction with 2, the reaction to give tetramer 10 wins out as a result of the high concentration of 2 (neat). When the ethyl diazoacetate (2) was thermally decomposed in a much more dilute solution (10% w/v in pxylene) there were significant quantities of the dimers 3 and 4 produced and a t the same time there was less of tetramer 10 relative to trimer pyrazoline 5. This is reasonable since each step in the sequence 314 5 10 requires more 2 and each depends on the concentration of 2. Again, as expected, no cyclopropane 8 was formed. Further, the Fe203-catalyzeddecomposition of 2 in more dilute solution (10% w/v in p-xylene) also provided significant amounts of 3 and 4, but now when 5 reacted, the catalyzed reaction 5 8 occurred2 a t the expense of the 5 10 reaction, which was dependent on the 2 concentration. Once more this is reasonable since with the lower concentration of 2 the reaction 5 10 is much slower while the reaction 5 8 is not significantly affected. Finally, as mentioned above, the attempted reduced-pressure distillation of dioxane (60-62 "C)from a dioxane/2/coal mixture, which resulted in decomposition of 2, gave a product distribution that was very similar to that obtained from 2 + Fe203dilute. Now, comparing these results with the coal results, we can first see that since cyclopropane 8 was always formed with the coal in largest amounts, these coal reactions would be most similar to the dilute 2 Fe203reaction. The most reasonable explanation for the similarity of these two systems is that within the coal the ethyl diazoacetate (2) is fairly well dispersed throughout the coal matrix. It is also clear that the formation of trimers and tetramers, particularly cyclopropane trimer 8, does not require very high concentrations of 2, particularly when the catalyst is present. Thus one can now conclude, as indicated above, that in the coal the ethyl diazoacetate (2) is probably distributed in regions of relatively low concentrations, which is consistent with our observations that the majority of the ethyl diazoacetate (2) appears to be reacting with the coal.
--
-
-
-
-
+
Conclusion A new pyrazoline tetramer 10 has been observed in the thermal and Fe203-catalyzed decomposition of ethyl diazoacetate (2) as well as when several coal samples were treated with 2 under various conditions. It was identified by its spectral properties and by independent synthesis. By comparison of the amounts of the ethyl diazoacetate (2)/(ethoxycarbonyl)carbene (1) dimers, trimers, and tetramer, 3-5, 8, and 10, formed in the coal reactions with the relative quantities formed in the thermal and
Fe203-catalyzedreactions of 2, both neat and relatively dilute, it has been concluded that there were various successive and competing reactions, one of which (5 8) was independent of the ethyl diazoacetate (2) concentration. In addition, on the basis of the observation that the product distribution of 3-5, 8, and 10 in the Fe203-catalyzed decomposition of 2 in relatively dilute solution is similar to that observed in the coal reaction, with cyclopropane 8 being the major product in both cases, and that the ethyl diazoacetate (2) is reacting mainly with the coal, it is concluded that 2 is farily well dispersed within the coal. Further, coal samples that had been treated with dioxane, a solvent known to swell the coal, seemed to give more extractable material (toluene/methanol solvent) after treatment with 2 and mild heating than when dioxane was not used. However, we have shown that this was not due to the diazo compound 2 being better able to get into the coal matrix in the swelled samples, and thus react more, but rather to the inability of the solvent to extract all of the reaction products that were still trapped in the coal. Coal reacted with 2 but not swelled with dioxane showed that more products could be extracted with dioxane after initial extraction with toluene-methanol, and that the total extractables and the amounts of 3-5,8, and 10 were now comparable to that obtained from swelled coal. A control showed no additional dioxane extractables from the swelled coal samples.
-
Experimental Section General Data. Melting points were determined on a Thomas-Hoover capillary melting point apparatus and were uncorrected. Capillary GC was run on a Varian Model 3700 gas chromatograph using a 0.32 mm X 30 m DB5+ column with injector temperature at 250 "C, FID detector at 300 "C, and temperature programmed at 6 "C/min from an initial temperature of 70 "C (held for 2 min) to a final temperature of 270 "C. Data collection was done by using a Dynamic Solutions/Millipore Maxima 820 chromatography workstation using an NEC APC IV color personal computma FT-IR spectroscopy was carried out on a Biorad-Digilab FTS-40 instrument equipped with a TGS detector and a Barnes Analytical-Spectra Tech diffuse reflectance accessory. Approximately 12 mg of sample and 100 mg of KBr were used for each FT-IR run. 'H and 13CNMR spectroscopic analyses were performed on a Bruker MSL 300 NMR spectrometer at 300.1 MHz for 'H and 75.5 MHz for 13C. Data were collected by using 8K data points, a 90" pulse angle, 2-s delay between pulses, and a 3205 Hz sweep width for 'H and 16K data points, 90' pulse angle, 5-s delay between pulses, and a 20000 Hz sweep width for 13C. For 5 and 10 the 13CNMR chemical shifts around 6 14 ppm were obtained by zero filling to 32K and 64K respectively. The %JHH coupling constants for the hydrogens attached to C-4 and C-5 of 10 were obtained by analysis of the appropriate blocks of the 2-D 'H NMR COSY spectrum, which was obtained by using 1K data points zero filled to 2K data points, a 90" pulse angle, 3-s delay between pulses and a 1299 Hz sweep width. Samples were prepared in 10-mm NMR tubes by using approximately 100 mg of sample in 3 mL of CDCl:, containing 1% v/v of TMS. GC-MS was performed on a Finnegan TSQ 70 MS/MS/DS system using a DEC Micro VIP computer and 70 eV for both E1 and CI (CH4). The samples were introduced with a Varian Model 3400 gas chromatograph using a 30 m X 0.32 mm DB5 + capillary column. The CHN analysis was performed by Texas Analytical Laboratories, Tallahassee, FL. Preparative chromatography was on a Harrison Research Model 79241' Chromatotron, a centrifugally accelerated, radial thin-layer chromatograph, using Si-gel 60 PFm (EM Science). Materials. The Illinois No. 6 HVCB coal was obtained from The Pennsylvania State University Coal Research Section (PSOC-1351) and was described previously.' Pentane, methanol, and toluene were purified as described previously.' Ethyl diazoacetate ( 2 3 ) Andrew, M. Chromatography 1987, 21.
Decomposition of Ethyl Diazoacetate (2) was prepared from ethyl glycinate hydrochloride and distilled; bp 24-26 "C (1.5 Torr).u Diethyl .fumarate (3) and diethyl maleate (4) were obtained from Aldrich Chemical Co. and used without further purification. The triethyl ester of aconitic acid was prepared by Fischer esterification of aconitic acid (Pfizer, cis and trans)26and characterizedas reported previously.' Dioxane (Fisher) was distilled through a 12-in. Heli-Pak column, and the fraction boiling at 100-101 "C was collected and stored over 4-A molecular sieves. Triethyl 2-Pyrazoline-trans -3,4,5-tricarboxylate (5). Compound 5 was prepared by the method of Forbes and Wood.s From 3.45 g (0.02 mol) of diethyl fumarate (3) and 2.28 g (0.02 mol) of ethyl diazoacetate (2),there was obtained, after recrystallization from ethanol, 3.87 g (68%) of 5 as white crystals: mp 97-98 "C (lit!* 98 "C). N M R (CDClJ: 6 169.8, 169.0, 161.2, 140.1, 66.2, 62.6, 62.2, 61.5, 52.4, 14.2, 14.04, 13.98. Triethyl trans -Cyclopropane-1,2,3-tricarboxylate(8). Compound 8 was prepared by the method of Forbes and Wood? From 3.1 g (0.01 mol) of pyrazoline 5 there was obtained, after distillation, 1.9 g (71%)of 8 as a colorless oil: bp 135-140 O C (0.9 Torr) (lit.s 112-117 OC (0.2 Torr)). Ethyl [ 1-(3,trans -4,5-Tricarbethoxy-A,-pyrazoliny1)lacetate (10). Compound 10 was prepared by adaptation of the method of Saegusa.16 The pyrazoline 5 (1.0 g, 3.5 "01) and CuCl (J. T. Baker; 25 mg, 0.25 mmol) were combined in a 5-mL round-bottomed flask equipped with a magnetic stirring bar and heated to 100 OC. To this molten solution was added ethyl diazoacetate (2; 0.39 g, 3.5 mmol) dropwise from a syringe into the open flask over a 1.5-h period. A vigorous evolution of nitrogen was observed with each addition of ethyl diazoacetate. This solution was allowed to stir at 100 "C for an additional 3 h. The red oil (1.29 g) was purified on the Chromatotron with 20% EtOAc/80% hexanes as eluent. Fraction 1 contained recovered starting material 5 (0.78 g) as determined by GC-MS and fraction 2 contained 0.43 g (33%) of product 10 as a light green oil. Gas chromatographic analysis of this oil showed it to be >99% pure. 'H NMR (CDClS): 6 4.95 (d, 1 H, C-5 H, J = 10.6 Hz), 4.45 (d, 1 H, C-4 H, J = 10.6 Hz), 4.49 (d, 2 H, CHZ, J = 17.9 Hz), 4.3 (m, 8 H, OCH,, J = 7.0 Hz), 1.3 (m, 12 H, CH,, J = 7.0 Hz). 13C NMR (CDCl,): 6 169.4, 168.8, 168.2, 161.1, 136.3,69.3, 62.2,61.9, 61.3,61.2, 53.9, 52.4, 14.2, 14.0, 13.9 (2 C). FT-IR (e, cm-'1: 2964 (m, C-H); 1740,1705 ( 8 , C=O); 1559 (m); 1198 ( 8 , C-0); 1111 (m); 1024 (m). MS (EI): m/e 372 (1, M), 327 (4, M - OEt), 299 (100, M - COPEt), 253 (88), 227 (12), 225 (14), 181 (57), 153 (27). MS (CI, CHI): m/e 413 (2, M + C3H5),401 (7, M + C2H5),373 (60, M + l),327 (100, M - OEt), 299 (55, M - COZEt), 151 (14). Anal. Calcd for C16H24N208:C, 51.61; H, 6.50; N, 7.52. Found: C, 51.68; H, 6.49; N, 7.55. Reaction of Coal Samples with Ethyl Diazoacetate (2). For the sample called coal A, 2.3 g each of dried coal (described previously)' and ethyl diazoacetate (2) were combined with 10 mL of pentane and allowed to stir overnight in a 100-mL (24) Searle, N. E. Organic Syntheses; Wiles New York, 1963; Collect. Vol. IV, p 424. (25) Ingold, C. K. J. Chem. SOC.1921,119, 350. (26) Huisgen, R. Angew. Chem. 1955,67,439.
Energy & Fuels, Vol. 3, No. 3, 1989 361 round-bottomed flask equipped with a magnetic stirring bar, nitrogen inlet, and an outlet connected to a mineral oil bubbler. The pentane was then removed under reduced pressure. For the samples called coals B and C, approximately 12 g of the dried coal was first swelled with 150 mL of freshly distilled 1,a-dioxane overnight in a 250-mL round-bottomed flask equipped with a magnetic stirring bar, nitrogen inlet, and an outlet connected to a mineral oil bubbler. This coal was then filtered, washed with approximately 50 mL of fresh l,4-dioxane, and then dried in an oven for 3 h at 110-115 "C under a nitrogen atmosphere. For the sample called coal B, 5.0 g of this dried coal was combined with 5.0 g of ethyl diazoacetate (2) and 10 mL of pentane and allowed to stir overnight as described above. The pentane was then removed under reduced pressure. For the sample called coal C, 4.5 g of the dioxane swollen coal and 4.5 g of ethyl diazoacetate (2) were allowed to stir overnight in a 100-mLround-bottomed flask equipped with a stirring bar, nitrogen inlet, and an outlet connected to a mineral oil bubbler. In each case, after the solvent was removed from the coal, the ethyl diazoacetate (2) was decomposed by heating the coal/$ samples slowly to 130 "C. Approximately 3 g of the heated coal samples were then extracted by using toluene-methanol (91) in a Soxhlet extractor for 12 h. The tolueneMeOH was removed in vacuum and approximately 50 mg of each extract was then weighed into a 5-mL volumetric flask and diluted to the 5-mL mark with acetone for subsequent quantification of 3-5,8, and 10 by GC analysis with authentic samples. Thermal and Catalytic Decomposition of Ethyl Diazoacetate (2). For the sample called 2 neat, 0.6 g of 2 was thermally decomposed in a clean, dry test tube (18 X 150 mm) described previously2)by heating slowly to 130-135 "C. This temperature was maintained until the evolution of nitrogen stopped (monitored by a bubbler). For the sample called 2 dilute, 0.5 g of 2 was combined with 5 mL of p-xylene in a test tube (18 X 150 mm) and heated similarly. For the sample called 2 + Fe2Os neat, 10 mg of Fe203and 500 mg of 2 were combined in a test tube (18 X 150 mm) and heated as above. For the sample called 2 + Fe203 dilute, 10 mg of Fe203,500 mg of 2, and 5 mL of p-xylene were combined in a test tube (18 X 150 mm) and heated similarly. The total run time in each case was approximately 1.5 h. Each sample was analyzed by GC for the relative ratios of 3-5, 8, and 10.
Acknowledgment. We thank the U.S.Department of Energy, Pittsburgh Energy Technology Center (Grant No. DE-FG22-86PC90532),for support of this work. Purchase of the Bruker MSL 300 NMR spectrometer and Varian gas chromatograph through grants from the Defense Advanced Research Projects Agency monitored by the Office of Naval Research and the National Science Foundation, respectively, is gratefully acknowledged. We also thank Dr. John Tseng, Mark Victor, and John Harwood for the NMR spectra and helpful suggestions and Professor Timothy D. Shaffer for the use of his GPC equipment. Registry No. 2,623-73-4;3,623-91-6;4, 141-05-9;5,11965677-8; 8, 13949-99-0;10, 119656-78-9; Fe203,1309-37-1; dioxane, 123-91-1.
