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3. Reagent-gradc acetone was used. The submitters state that an excess of acetone is necessary. When a 1:1 mole ratio of acetone to furan was used, they obtained only a 21% yield of crude product, and when a 1:2 ratio of acetone to furan was employed, the yield of product was less then 5%.
4. The submitters report that, if this material is not washed thoroughly to remove the soluble linear polymers of low molecular weight present, the crude product will melt and/or darken at much lower temperatures than 231-240°.
5. The product has the following spectral properties; nuclear magnetic resonance (chloroform-d) S (multiplicity, number of protons, assignment): 5.90 (singlet, 8, aryl CH), 1.48 (singlet, 24, CH3); mass spectrum m/e (relative intensity): 432 (M+, 40) 418 (34), 417 (100), 201 (28), 186 (31), 149 (56), 85 (46), 83 (67), 75 (21), 60 (21), 47 (20), 45 (24), 43 (53), and 41 (26).
6. Catalyst obtained from Engelhard Industries was used. The submitters used 200 mg. of Fluka 10% palladium on charcoal catalyst with 5 g. of starting material in 250 ml. of ethanol and obtained a total yield of 2.3 g. (46%), m.p. 208-211°.
7. The ethanolic filtrate can be concentrated to 10-15 ml. under reduced pressure to obtain 0.3 g. (7%) of crude product, m.p. 187-202°. Unchanged starting material, if present, is concentrated in this second fraction and may be detected by the furan resonance at 8 5.85 in the proton magnetic resonance spectrum or by a sharp infrared absorption
at 772 cm.-1 which is not present in the product. Elemental analyses of these second crops suggested that other impurities were also present.
8. The solid tenaciously holds a small amount of chloroform which can be detected by proton magnetic resonance (S 7.25). Vacuum drying overnight at 60° removes this impurity.
9. In one isolated case the checkers found that no hydrogen uptake
occurred, and unreacted starting material was recovered. This erratic result may have resulted frorr cidental poisoning ofJthe catalyst by
contaminants present in the av Jave or associated valves and lines'.'If multiple runs are carried out, the products of each should be checked by infrared or proton magnetic resonance spectroscopy before being combined. The spectral properties of the product are: proton magnetic resonance (chloroform-d) S (multiplicity, number of protons, assignment): 0.74, 0.82, 0.93, 1.04 (singlets, 24, CH3); 1.2-1.9 (multiplet, 16 CH2), 1.9-2.8 (multiplet, 4, C//2), and 3.0-4.2 (multiplet, 8, ÑH); infrared (Nujol) cm.-1 strong absorptions: 1078, 1039, medium: 999, 991, 552, 528, 520, and weaker: 1285, 1248, 1204, 977, 884, 840, 659, 719, 598, 560. The checkers concluded from examination of properties that a variable mixture of isomers is obtained from the hydrogenation.
The unsaturated tetraoxaquaterene (accompanied by linear condensation products) was first synthesized in 18.5% yield by the acid-catalyzed condensation of furan with acetone in the absence of added lithium salts.2 Other ketones also condensed with furan to give analogous products in 6—12% yield.2-4 A corresponding macrocycle was also prepared in 9% yield froln pyrrole and cyclohexanone.4 The macrooyclic ether products have also been obtained by condensation of short linear condensation products having 2, 3, or 4 furan rings with a carbonyl compound.5
The method described here gives higher yields of the macrocyclic tetraethers and allows the product from furan and cyclohexanone to be formed directly in 5-10% yield, whereas this product was previously obtained only by an indirect route. The added lithium perchlorate undoubtedly accelerates the reaction, since after short reaction times the product was isolated in 20% yield when the salt was present and in only 5% yield when the salt was absent. The lithium cation is presum-ably acting as a template which coordinates with the oxygen atoms of
the furan units to favor cyclization instead of linear polymerization.6 The hydrogenated macrocycle has been shown to form complexes with lithium salts.6,7
1. Laboratoire de Chimie Organique Physique, Laboratoire de Chimie Organique II,
University Claude-Bernard Lyon I, 43, Boulevard du 11 Noverabre 1918, 69-
2. R. G. Ackman, W. H. Brown, and G. F. Wright, J. Org. Chem., 20, 1147 (1955).
3. R. E. Beals and W. H. Brown, J. Org. Chem., 21, 447 (1956).
4. W. H. Brown, B. J. Hutchinson, and Ì. H. MacKinnon, Can. J. Chem,., 49, 4017 (1971).
5. W. H. Brown and W. N. French, Can. J. Chem., 36, 537 (1958).
6. M. Chastrette and F. Chastrette, Chem. Commun., 534 (1973).
7. Y. Kobukc, H. Hanje, K. Horiguchi, M. Asada, Y. Makayama, and J. Furukawa, J. Amer. Chem. Soc., 98, 7414 (1976).
OXIDATION WITH BIS(SALICYCODENE)ETHYLENEDHMINO-COBALT(Ï) (SALCOMINE): 2,6-DI-fert-BUTYL-p-BENZ0QUIN0NE
Oa, salcomine dimethylformamide 30-50"