J . Org. Chem., Vol. 40, No. 21, 1975 3151
Notes perature for 24 hr. The mixture was poured on crushed ice and the mono-N-acetyl derivative which separated out was filtered off, washed, and crystallized from ethanol. B. A suspension of the phenylglyoxal monohydrazone (1g) was heated under reflux with acetic anhydride (15 ml) for 5 hr. The mixture was poured on crushed ice and the mono-N-acetyl derivative which separated out was worked up as in A; (see Table 11). Registry No.-Ia,
Table I Na -NH? -EtOH a products'
Benzyl alcohol
Registry no.
5335-28-4; Ib, 56421-95-5; IC, 13732-32-6; Id, 6630-86-0; IIa, 33877-94-0; IIb, 56404-20-7; acetyl chloride, 75-365; acetic anhydride, 108-24-7.
100-51-6
@-CH,OH
References and Notes
617-94-7
w- - O H
(1) L. F. Fieser and M. Fieser, "Oraanic Chemistry", D. C. Heath, Boston, Mass., 1944, p 351. (2) 0.L. Chagman, Chapman, W. J. Welstead, T. J. Murphy, and R. W. King, J. Am. Chem. Sic., Soc., 86, 732 (1964). (3) H. El Khadem. M. L. Wolfrom, and D. Horton, J. Org. Chem., 30, 838 119651 (4) H.-El-Khadern, 2. M. El-Shafei, and M. M. A. Abdel Rahman, Carbohydr. Res., 1, 31 (1965). (5) H Simon and A. Kraus, Fortschr. Chem. forsch., 14, 430 (1970). (6)H. El Khadem, 2 . M. El-Shafei, and M. M. Hashem. J. Chem. Soc. C, 949 (1968). (7) H. El Khadem, M. M. El-Sadik, and M. M. Meshreki. J. Chem. Soc. c, 2097 (1968). (8) M. L. Wolfrom, G. Fraenkel, D. R. Lineback, and F. Komitsky, J. Org. Chem., 29, 457 (1964). (9) L. Mester, E, Moczar, and J. Parello. Tetrahedron Lett., 3223 (1964). (101 . . 0. L. Chaaman, R. W. King, W. J. Welstead. Jr., and T. J. Murphy, J. Am. C h e i . Soc., 88,496811964). (11) H. El Khadem, M. A. E. Shaban, and M. A. M. Nassr, J. Chem. SOC.C, 1614 (1969). (12) H. El Khadem, M. A. M. Nassr, and M. A. E. Shaban, J. Chem. :Soc., 1465 (1966). (13) J. A. Pople, W. G. Schneider, and H. J. Berstein, "High-Resolution Nuclear Magnetic Resonance", McGraw-Hill, New York, N.Y.. 1959, p 221. (14) H. El Khadem and M. M. Mohammed-Aly, J. Chem. SOC.,4929 (1963). (15) H. El Khadem, Adv. Carbohydr. Chem., 20, 139 (1965).
Lithium-Ammonia Reduction of Benzyl Alcohols t,o Aromatic Hydrocarbons. An Improved Procedure Gary H. Small, Arlene Engman Minnella, and Stan S. Hall* Carl A . Olson Memorial Laboratories, Department of Chemistry, Rutgers University, Newark, New Jersey 07102 Received M a y 29,1975
Some time ago Birch reported the reduction of a few benzyl alcohols to the corresponding aromatic hydrocarbons in sodium-ammonia-ethanol so1utions.l The general procedure was t o add small pieces of sodium periodically to a solution of the benzyl alcohol and ethanol in liquid ammonia. What was disconcerting t o us was t h a t these conditions were almost exactly those reported previously by the same researcher to reduce aromatic compounds to the corresponding 1,4-dihydro derivatives.2 Since this work had been done long before gas-liquid partition chromatography or nuclear magnetic resonance spectroscopy, it seemed conceivable t o us that under these conditions some overreduction might have occurred and mixtures obtained b u t not detected. 0H
-
Li -NH3 -i\"4Cla products'
1,41,4Aromatic Dihydro Aromatic Dihydro derivhydroderivhydroative carbon ative carbon
100"
100"
100"
100"
CH ,
CH
105-13-5 529-33-9
6351-10-6
-
C H O O C H P H
aS dH /
64
lZd
100"
75
25
100"
85
15
100'
($Ha OH
91-01-0
94
6e
91
9
82
18e
88
12
OH
76-84-6
0 The reaction conditions are described in the Experimental Section. Analyzed by GLC (70of volatiles). c Isolated in excellent yield (greater than 95%) in repeated experiments after column chromatography. Plus 2J-dihydro alcohol (10%) and unreacted alcohol (14%).e Predominantly the mono-l,4-dihydroderivative.
tion of benzyl alcohols. The lithium-ammonia-ammonium chloride method involves the addition of the benzyl alcohol in T H F to a solution of lithium in ammonia, and then the resultant mixture is rapidly quenched with ammonium chloride. OH
dzm
Table I summarizes the outcome of this study. The results of sodium-ammonia-ethanol reduction of benzyl alcohol, phenyldimethylcarbinol, and p -methoxybenzyl alcohol are substantially the same as were previously rep0rted.l However extension of this procedure to other benzyl alcohols, such as 1-tetralol, 1-indanol, benzhydrol, and triphenylcarbinol, resulted, in most cases, in substantial overreduction. In contrast, the lithium-ammonia-ammonium chloride procedure was much more selective. All of the benzyl alcohols except benzhydrol and triphenylcarbinol yielded exclusively t h e corresponding aromatic hydrocarbon. Evidently the major difference between the two reduction procedures is that the aromatic hydrocarbon product is overexposed to the strong proton source in the sodiumammonia-ethanol procedure, while such contact is minimized in the lithium-ammonia-ammonium chloride method.
Experimental Section Since we had recently established that benzyl alcohols and their alkoxides are efficiently reduced t o aromatic hydrocarbons in lithium-ammonia solutions that were quenched with ammonium chloride,3 we undertook a careful comparative study of the two procedures using a selec-
General Comments. The reductions were performed under a dry N2 atmosphere in dry glassware. Sodium metal was cut in small pieces, lithium wire (0.32 cm) was cut in 0.5-cm pieces, and both were rinsed in petroleum ether just prior to use. Anhydrous NHs was distilled through a KOH column into the reaction vessel. THF was freshly distilled from LiAIH4. Analysis of reaction mixtures was accomplished by gas-liquid partition Chromatography
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J . Org. Chem., Vol. 40, No. 21, 1975
(GLC) using a 4 ft X 6 mm (all glass) 4% silicone gum rubber UCCW-982 (methyl vinyl) on 80-100 mesh HP Chromosorb W (AW, DMCS) column; and by gas-liquid partition chromatographymass spectrometry (GLC-MS). All products gave satisfactory spectral and analytical data; mixtures were compared by GLC and GLC-MS with authentic samples. Lithium-Ammonia-Ammonium Chloride. To a pear-shaped metal-ammonia reaction vessel containing a stirred mixture of 105 mg of Li (15 mg-atoms, six pieces) in 20 ml of NH3 and 10 ml of THF was added (10 min) a solution of 741 mg (4.99 mmol) of l-tetralol in 10 ml of THF. After 10 min, ca. 1.2 g of NH&1 was cautiously added (ca. 2 min) to discharge the blue color, and the NH3 was allowed to evaporate. After the residue had been partitioned between brine and EtZO, the organic phase was dried, filtered, concentrated, and analyzed by GLC and GLC-MS. Following column chromatography, 646 mg (98%) of tetralin was obtained as a colorless oil. Sodium-Ammonia-Ethanol. To a stirred mixture of 741 mg (4.99 mmol) of 1-tetra101 and 500 mg (10.96 mmol) of EtOH in 20 ml of NH3 was added six pieces of Na (253 mg, 11 mg-atoms) over a 14-min period t o maintain a dark blue solution. Approximately 1 2 min later the mixture turned white and then the NH3 was allowed to evaporate. Work-up as described above yielded a mixture of tetralin (75%)and 5,8-dihydrotetralin (25%). Registry No.-Toluene, 108-88-3; 1-methylethylbenzene, 9882-8; l-methoxy-4-methylbenzene, 104-93-8; 1,2,3,4-tetrahydro-
naphthalene, 119-64-2; 2,3-dihydrom1,4-indene, 496-11-7; 1,l'methylenebis(benzene), 101-81-5; l,l',l"-methylidynetris(benzene), 519-73-3.
References and Notes (1) A. J. Birch, J. Chern. Soc., 809 (1945). (2) A. J. Birch, J. Chem. Soc., 430 (1944). (3) (a) S. S. Hall, S. D. Lipsky, and G. H. Small, Tetrahedron Lett., 1853 (1971); (b) S. S. Hall, S. D. Lipsky, F. J. McEnroe, and A. P. Bartels. J. Org. Chern., 36, 2588 (1971); (c) S . S. Hall, A. P. Bartels, and A. M. Engman, /bid., 37, 760 (1972).
Transfer of Oxygen to Organic Sulfides with Dimethyl Sulfoxide Catalyzed by Hydrogen Chloride. Preparation of Disulfoxides C. Max Hull*' and Thomas W. Bargar* Department of Chemzstry, State University of Ne& York, Binghamton, N e & York 13901 Received J u n e 11, 1975
The transfer of oxygen from a sulfoxide to a sulfide has been reported,3 but with limited success as a preparative method. Thus, Bordwell and Pitt3a isolated dibenzyl sulfoxide in 17% yield from a tarry mixture obtained by refluxing an acetic acid solution of dibenzyl sulfide and fourfold excess 1-thiacyclopentane 1-oxide in the presence of sulfuric acid. Barnard3b observed oxygen exchange up to ca. 7% equilibration between 35S-labeled cyclohexyl methyl sulfoxide and a large excess of inactive cyclohexyl methyl sulfide by heating the mixture with acetic acid containing a trace of perchloric acid. Searles and HaysZCprepared di-npropyl, di-n- butyl, and tetramethylene sulfoxides by heating the respective sulfides with Me2SO for several hours at 160-175°, The reaction was accompanied by considerable pyrolysis. They were unsuccessful in catalyzing the reaction with acids. In connection with an investigation of metal ion complexes of 2,5-dithiahexane 2,5-dioxide (1): one of us attempted to prepare the ligand by transferring oxygen from MezSO t o 2,5-dithiahexane. In the absence of catalysts no
Notes reaction occurred, even on boiling the mixture for many hours a t approximately 180'. However, the addition of small amounts of hydrogen chloride to the mixture catalyzed the reaction a t about 100' and afforded the desired disulfoxide in good yield.5 Since the method has advantages over the procedures with conventional oxidizing agents, we report here the preparation of disulfoxides from sulfides of the type RS(CH2),SR ( n 2 2, R alkyl or benzyl). We were unable t o isolate sulfoxides from formals ( n = I), or from other mercaptals and mercaptoles. Instead we obtained oxidative cleavage, generating formaldehyde (or the analogous carbonyl compounds), the disulfide RSSR, and dimethyl sulfide-a consequence of the rapid acid-catalyzed decomposition of monosulfoxides RS(0)CR'2SR,6 which would form initially by 0-transfer from Me2SO. In recer*i years, the effects of halogen halides, and particularly HC1, on sulfoxide behavior, including racemization? and 0-exchange8 reactions, have been investigated inten~ i v e l yA . ~common intermediate appears to be the halosulfonium ion, e.g., Me2SC1, whose formation, via protonated sulfoxide, is kinetically dependent on both H + and halide ion, and usually rate determining. The completion of the process would involve relatively fast reactions with nucleophilic agents, e.g., H20 regenerates the sulfoxide, halide ion effects racemization (specifically by C1- or Rr-), or reduction to sulfide (especially by I-). Modenag includes sulfides among the nucleophiles which would react with halosulfonium ions. Accordingly, 0-transfer with MezSO would proceed as follows. Me,SO
ZHCI
several
R,SO
2HC1
steps
This course would appear to be more reasonable than direct involvement of protonated sulfoxide by nucleophilic attack of sulfide on o ~ y g e n , ~ ~and J O would explain catalysis by halogen acid specifically as opposed to acids in general. The advantages of the HC1-catalyzed Me2SO method include cheapness of reagent, the absence of overoxidation which inevitably occurs with conventional oxidizing agents," and the relatively simple isolation and purification of the product. The reaction is unfortunately limited to nonaromatic sulfides. The disulfoxide preparations are summarized in Table I. T h e crude products usually have a wide melting range, expected of a mixture of diastereoisomers ( d l pair and meso). Recrystallization was used to isolate a t least one isomer, both in the case of 3 and 4. Infrared Spectra. All products absorb most intensely a t ca. u 1000--1050 cm-', typical of the sulfoxide SO stretching frequency (see Table I). As a test of oxidation methodsMe2SO vs. commonly used oxidizing agents-we prepared l a and 2 with H202 in acetic acid,12a,b and la also with sodium metaperiodate,13 and determined their ir spectra. In the sulfoxide region the analogous spectra are indistinguishable. Thus, whether produced by Me2SO or the other methods, la shows a broad band with a maximum a t ca. 1018 cm-l and 2, distinct bands a t 1019 (more intense) and 1044 cm-I.l4 However, elsewhere in the spectrum, as shown in Table 11, there are significant differences. We offer the following explanations for extra bands in the spectra of products of peroxide and periodate oxidation. Compound la. Shoulders a t 1307, 1318, and 1324 cm-' and the band at 1139 cm-l suggest the sulfone group.16a,b T h e bands a t 508 and 520 cm-l (peroxide method) and a t 538 and 551 cm-I (periodate method) may also be associated with su1f0ne.l~~ A band a t 1267 cm-' appears in the
