J. Org. Chem. 1 9 8 4 , 4 9 , 4 1 6 1 - 4 1 6 5
4161
Silica Gel as an Effective Catalyst for the Alkylation of Phenols and Some Heterocyclic Aromatic Compounds Yasuhiro Kamitori, Masaru Hojo,* Ryaichi Masuda, Tatsuo Izumi, and Shtiichi Tsukamoto Department of Industrial Chemistry, Faculty of Engineering, Kobe University, Rokkodai, Kobe 657, Japan
Received M a r c h 9, 1984 I n the presence of silica gel, the reaction of phenol with t-BuBr was examined u n d e r a variety of conditions a n d it was found t h a t silica gel is a n effective catalyst for t h e alkylation. As a result of this work 2-tert-butyl-, 2,6-di-tert-butyl-, a n d 2,4,6-tri-tert-butylphenols, all of which are h a r d t o obtain directly b y t h e Friedel-Crafts process, could be prepared easily b y this one-step reaction. Several other alkyl halides were also used in this reaction. The alkylations of some heterocyclic aromatic compounds which cannot be alkylated by the conventional Friedel-Crafts method were also successfully performed by this reaction.
Introduction Recently many organic chemists have been intrigued with the use of inorganic supports for use as effective and selective catalysts in some synthetic organic reaction.lP2 In the past ten years we have reported a series of new reactions*'l using silica gel as a versatile catalyst. When silica gel is used in combination with other reagents the intrinsic reactivity of the reagent can be well controlled to realize highly chemoselective reactions"" and, in some cases, even the nature of the reagents can be changed completely to present valuable new reaction^.^,"^ In addition, silica gel itself serves as a mild and therefore selective Lewis acid cataly~t.~ The Friedel-Crafts reaction has long been known as an important way of introducing alkyl groups into aromatic nuclei, and aluminum chloride is the most widely used catalyst for this reaction. However aluminum chloride is too strong a catalyst for some of the substrates and products. In these cases, undesirable degradation, polymerization, isomerization, and so on occur extensively. The result is a meager yield of expected products. As milder and therefore more selective catalysts some inorganic supports seemed to be quite promising substitutes. So far these have been frequently used for gas-phase alkylation of aromatic compounds at higher temperatures,12 but no liquid-phase alkylation in milder conditions has yet been reported. Previously, we presented successful condensations of arenesulfenyl chlorides and aryl chloromethyl sulfides with aromatic compounds using silica gel as a c a t a l y ~ t .As ~ an extention of this work liquid-phase alkylation of phenols and some heterocyclic aromatic compounds in the presence of silica gel as a mild and selective Lewis acid catalyst has been studied in some detail and we now wish to report the results. Results and Discussion tert-Butylation of Phenol Using Various Inorganic Supports. Phenol is highly susceptible to attack by (1) Hojo, M.; Masuda, R. J. Synth. Org. Chem. Jpn. 1979,37,557,689, and references cited therein. (2)MaKillop, A.;Young, D. W. Synthesis 1979,401,481,and references cited therein. (3)Hojo, M.; Masuda, R. Synth. Commun. 1975,5, 173. (4) Hoio. M.: Masuda. R. Svnth. Commun. 1975.5. 169. (5)HGo; M.; Masuda; R. fetrahedron Lett. 1976,613. ( 6 ) Hojo, M.; Masuda, R. Synthesis 1976,678. (7)Hojo, M.; Masuda, R.; Saeki, T.; Fujimori, K.; Tsutsumi, S. Tetrahedron Lett. 1977,3883. (8)Hojo, M.; Masuda, R.; Hakotani, K. Tetrahedron Lett. 1978,1121. (9)Kamitori, Y.;Hojo, M.; Masuda, R.; Inoue, T.; Izumi, T. Tetrahedron Lett. 1982,23,4585. (10)Kamitori, Y.;Hoio, M.; Masuda, R.; Izumi, T.; Inoue, T. Synthesis 1983,387. (11)Kamitori, Y.;Hojo, M.; Masuda, R.; Inoue, T.; Izumi, T. Tetrahedron Lett. 1983,24, 2575. (12)Venuto, P.B.;Hamilton, L. A.; Landis, P. S.; Wise, J. J. J. CQtalysis 1966,5,81.
T a b l e I. t e r t - B u t y l a t i o n of P h e n o l in the Presence of V a r i o u s I n o r g a n i c SuDDorts" product ratio, % no. catalyst conversn, % 1 2 3 1 41 58 32 10 2 wet Si02c 0 0 0 0 3 basic Al2OSd 19 63 32 5 4 neutral A1203e 40 36 48 16 5 acidic Al2Oi 5 80 20 0 6 molecular sieves# 34 29 41 24 "Phenol (2 mmol), t-BuBr (4 mmol), and inorganic supports (1 g) were used. Reactions were carried out in CH2Cl2a t 30 O C . Reaction time was 24 h for all runs. Wakogel C-300 dehydrated a t C-300 non170 "C for 3 h under pressure of 0.1 torr. "akogel dehydrated. dWoelm/Alumina B Super I dehydrated a t 200 "C under pressure of 0.1 torr. eNakarai/Alumina activated 300 dehydrated a t 200 "C for 5 h under pressure of 0.1 torr. fWoelm/ Alumina acid TLC dehydrated a t 200 "C for 5 h under pressure of 0.1 torr. gNakarai/Molecular Sieves 4A
electrophilic reagents but it is not as reactive toward alkyl halides in the absence of the catalyst. In fact, none of the alkylated product was detected after treatment of phenol with twice molar amounts of t-BuBr in refluxing CHzClz for 10 h. However, it was found that in the presence of silica gel or some other inorganic support, tert-butylation of phenol by t-BuBr occurred easily even a t room temperature. As is shown in Table I, 2-tert-butyl-, 4-tertbutyl-, and 2,4-di-tert-butylphenols (1, 2, and 3, respectively) are obtained in moderate yields with the use of
6
inorpclnic t-Lk support
-&Q 1
2
t
g$% 3
inorganic supports as catalysts. No tert-butyl phenyl ether was formed in any case. These results are in the sharp contrast to the case of tert-butylation by t-BuC1 (or isobutene) in the presence of AlCl, or HF, where 2 is the preferential product.13J4 The product ratio varied with a change of catalysts, and even reversal of the ratio was observed. Table I also exhibits fairly good conversion as well as major formation of 1 when silica gel was used as a catalyst (no. 1) and, at the same time, demonstrates the necessity of drying silica gel before use (no. 1and 2). Thus silica gel was found to be active enough to catalyze alkylation of phenol by t-BuBr even under mild conditions. The reaction proceeded cleanly and no detectable amounts of byproduct could be observed even by careful inspection of the crude material by 'H NMR. (13) Isagulyants; Bagryantseva Neft. Khoz. 1938,No. 2,36; Chem. Abstr. 1939,33,8183. (14)Price, C. C. Org. React. (N.Y.) 1967,3,1.
0022-326318411949-4161$01.50/0 0 1984 A m e r i c a n C h e m i c a l Society
4162 J . Org. Chem., Vol. 49, No. 22, 1984
Kamitori et al.
Table 11. tert-Butylation of Phenol in the Presence of Silica GePb no. 1 2 3 4 5 6 7
t-BuBr, mmol 4 4 6 4
SiOz, g 1 1 1.5 1 3 2 2
18
12 12
NaZCO3,mmol 0 6 9 6 0 0 24
temp, "C 30 30 30 80 80
70 70
time, h 24 24 48 24 48 40 40
conversn, % 41 33 40 94 72 94 83
1 58 61 42 29 2 0 -0
product ratio, 2 3 32 10 21 18 1 31 32 38 13 73 35 61 3 54
'7~ 4 -0 -0 13 1 -0 0 -0
5 -0 -0 13 0 12 4 42
"As a substrate 2 mmol of PhOH was used. bAs a solvent 5 mL of CH2C12was used for no. 1-3, 5 mL of CICHzCHzClfor no. 4-5, and 5 mL of CCll for no. 6-7. Table 111. tert -Butylation of Polyhydroxybenzenes in the Presence of Silica Gel" t-BuBr, no. substrate, 2 mmol mmol Na2C03, mmol solvent temp, "C time, h product conversn, % 1 6 2 O C CH2ClZe 30 24 8 12a 11 12b 24 100 12c 2 6 6 18d CClJ 70 24 30 19 13a 3 7 2 0' CHZC12' 24 70 13b 4 7 6 18d CClJ 100 24 21 14a, 30 5 8 2 OC CHZC1ze 24 14b 100 6 8 6 18d CClJ 70 24 12 70 15a 7 9 18 18 CClJ 15b 55 15c 23 15d 10 70 24 16 72 3 0 CC14P 8 10 CC14B 70 40 56 9 11 2.5 4 17a 17b 19
yield,* 70 3 6 87 9 85 15 92 6 42 11 7 63 42 19
Each 1 g of SiOz was used for all experiments. Isolated yield. 'Method A (see Experimental Section). dMethod B (see Experimental Section). e 4 mL was used. '7 mL was used. 8 5 mL was used.
tert-Butylation of Phenol Using Silica Gel as an Effective Catalyst. As silica gel was found to be sufficiently active toward the liquid-phase tert-butylation of phenol, we examined this reaction in some detail. The representative data are summarized in Table 11. The main product, 1, was obtained together with some 2 and 3, when twice molar amounts of t-BuBr were used at 30 "C (no. 1 and 2). Two or three times as much as 1 over 2 was produced. Such a preferential formation of 1 is notable since 2 is obtained predominantly by usual Friedel-Crafts reaction. Pure 1could be obtained easily by simple column chromatography. It was also found that addition of Na2C03slightly increased the amount of 1. Thus the present alkylation with the use of silica gel should be a versatile method for preparation of 1 which is now commonly prepared15 by tert-butylation of 4-bromophenol followed by debromination using Raney nickel. When t-BuBr was used in greater excess, di- and tri-tert-butylphenols became the main products. It is also noteworthy that 2,6-di-tert-butylphenol4, which is not produced by
6
-
Si02,(Na2C03) t-hB
1 t
2 t
3t9+9
the usual method using conventional Lewis acid catalysts, can be obtained easily under suitable conditions (no. 3). A t higher temperatures (no. 4-7), amounts of 1 and 4 decreased and those of 3 and 5 increased. Addition of Na2C03increased the yield of 5 effectively (no. 7 ) though the total conversion was diminished slightly. Thus the present method can also be used as a convenient preparative method for 3 and 5. In such an electrophilic alkylation process, there should be equilibria among the starting material and products as (15) Hart, H. J . Am. Chem. SOC.1949, 71,1966.
Scheme I
1
t
2
described below. In the presence of powerful catalysts such as AlCl, and H2S04the equilibria would be rapid and hence would favor the thermodynamically more stable 2. On the other hand, in the presence of silica gel as a milder catalyst the equilibria should become less rapid and the reaction would be controlled kinetically16 to result in preferential formation of 1. At higher temperatures, more rapid equilibria should favor formation of 2 and 3 in place of 1 and 4. Addition of Na2C03,which traps HBr generated during the reaction, is thought to inhibit protonation and subsequent de-tert-butylation, and consequently increases the amount of 5 (no. 7 ) . tert -Butylation of Polyhydroxybenzenes. tert-Butylation in the presence of silica gel was extended to polyhydroxybenzenes. The results are summarized in Table 111. When 6 , 7 , and 8 were treated with sufficiently excess amounts (6 times molar amounts) of t-BuBr in the presence of silica gel (with Na2C03,at 70 "C), corresponding di-tert-butylated products 12c, 13b, and 14b, respectively, were obtained quantitatively, whereas use of twice molar mounts of t-BuBr (without Na2C03,at 30') afforded only mono-tert-butylated products, 12a, 12b, 13a, and 14a. Similarly bis(pheno1) 9 and 2-naphthol 10 could be alkylated successfully. Anisole l l was also tert-butylated to afford 17a and 17b, and none of the C-0 bond cleaved product which occurs sometimes when AlCl, is used as a catalyst1' was observed by 'H NMR inspection. Thus silica (16) This is probably due to some interaction between t-BuBr and the phenolic OH gioup. (17) Tsukervanik, I. P.; Nazarova, Z. N. J . Gen. Chem. USSR (Engl. Transl.) 1937, 7, 623; Chem. Abstr. 1937, 31, 5778.
J. Org. Chem., Vol. 49, No. 22, 1984 4163
Silica Gel as Catalyst for Alkylation
Scheme I1
Table IV. Alkylation of 18 in the Presence of Silica Gela no. 18 RX temp, "C time, h product yield,b % refl 24 19 85 1 a t-BuBr' 24 20 47 2 a CzH,(CH3)2CBrc refl refl 24 21 6 3 a p-TolCHzClc 22 57 refl 24 23 83 4 a CH,=CHCH-
(CH,) C1' 5
a CH30CH2ClC
20
5
24a
87
6
(244 a 24cd
20
0.5
7
b 24cc
20
5
24a 25 24b
42 26' 78
"Each 2 mmol of substrate, 2 g of SiOz, and 5 mL of CC14 as solvent were used for all experiments. Isolated yield. e 4 mmol of RX and 6 mmol of NazC03 were used. d12 mmol of RX and 18 mmol of Na2C03 were used. 'Yield calculated from 'H NMR
spectra. gel is a versatile catalyst for use in tert-butylation of polyhydroxybenzenes, too. Other Alkylating Agents Usable on Silica Gel. tert-Amyl bromide, p-xylyl chloride, 3-chloro-l-butene, and chloromethyl methyl ether were also found to be usable as alkylating agents. The results are shown in Table IV, where 2,6-xylenol (Ma) and 2,6-di-tert-butylphenol (18b) were used as substrates. In every case, the substrates were alkylated successfully. When p-xylyl chloride was used as a reagent considerable amounts of 3,4-disubstituted product 22 was obtained together with the expected 21 (no. 3). In the case of Ma, on treatment with 3-chloro-l-butene, the 2-butenyl group was introduced in an almost quantitative yield (no. 4). Reaction of 18b with chloromethyl methyl ether afforded 24b in high yields. All these reactions proceeded quite cleanly and no dealkylation was observed. In contrast, attempted alkylations by tert-butyl chloride, sec-butyl bromide, methyl iodide, and phenacyl bromide resulted in failure. In these cases, extensive dehydrohalogenation of the alkyl halides occurred and most of the substrates were recovered unchanged. Alkylation of Heterocyclic Aromatic Substances. It was well-known that Friedel-Crafts type alkylation usually do not proceed successfully14on heterocyclic aromatic compounds such as furan, thiophene, and so on, because of their instability toward strong Lewis acid or mineral acids. As a potentially useful and interesting application, the present method was extended to alkylation of heterocyclic aromatic compounds. In the presence of silica gel, thiophene, furan, benzothiophene, and 1methylindol were all cleanly converted to the corresponding alkylated products 26-30 in good yields. The results are summarized in Table V. Alkylation occurred a t the 2- and 5-positions of thiophene and furan, a t the 3-positions of their benzo analogues, and at the 3-position of 1-methylindol.
Experimental Section Unless otherwise noted, commercially available silica gel for column chromatography (WakogelC-300) was used throughout this study, after drying at 170 O C for 5 h under reduced pressure (0.1 torr). Each solvent was dried on molecular sieves 4A, 1/16 no. 1
2 3 4 5
16
l'la.Rl=t-Bu,R'=H 17b. R 1 =H,R'=t-Uu
Scheme 111 Si02 in C C I ~ A .
R
19
- 25
U a , R = Me 2 4 b . R= t - B u
Scheme IV
R' 26, x = n,
R I =R:=
27, \ = 0 , 28, I = S .
R ' = \ l e , R'= I - B i t R I = R'=
r-Rit
29. \ = S 311. \ = SYC
I-Bo
before use. Commerciallyavailable anhydrous sodium carbonate was powdered finely and used directly. All 'H NMR spectra were recorded at 60 MHz on JEOL PMX 60 SI or Hitachi R-24 spectrometers,in CDCl, solutionscontaining tetramethylsilane as an internal standard. Analytical GC was performed with a Varian Aerograph Model 90-P gas chromato-
Table V. Alkylation of Heterocyclic Aromatic Compounds in the Presence of Silica Gel substrate, mmol t-BuBr, mmol SO2, g NaZCO3,mmol CC14, mL temp, "C time, h product thiophene, 4 12 1 12 4 78 40 26 2-methylthiophene, 4 16 1 16 6 78 24 27 furan, 8 42 4.3 72 16 b 48 28 benzothiophene, 4 24 1 9 4 78 24 29 1-methylindol, 4 16 1 16 4 78 24 30
"Isolated yield. *The reaction was carried out at 25
"C for 24 h and then at 78 "C for another 24 h.
yield," %
98
61 51
78 50
4164 J . Org. Chem., Vol. 49, No. 22, 1984 in. graph. The GC column used was 5% SE30, 10 f t X General Procedure for tert -Butylation of Phenol in the Presence of Si02,A1203,and Molecular Sieves (Table I). To a mixture of phenol (2 mmol) and the inorganic support (1 g) in dry CH2C12(5 mL) was added t-BuBr (4 mmol) and the mixture was then stirred for 24 h at 30 "C. The inorganic support was filtered off and washed thoroughly with diethyl ether. The washings and the filtrate were combined, and the solvent was removed. The products were analyzed by well established GC methods and 'H NMR measurements. General Procedure for tert -Butylation of Phenol in the Presence of S i 0 2 (Table 11). To a mixture of phenol (2 mmol), SO2,and, if necessary, Na2C03in a dry solvent was added t-BuBr, and the whole mixture was stirred for 24-48 h at 30-80 "C. Silica gel was filtered off and washed thoroughly with diethyl ether. The washings and the filtrate were combined and the solvent was removed. A small portion of the raw product was analyzed by GC method and the remainder was dissolved into 40 mL of CH2C12 and washed with 50 mL of 1N aqueous NaOH. The organic layer was dried over anhydrous Na2S04and the solvent was removed under vacuum. The residue was fractionated by Si02 column chromatography. Representative results (Table 11, no. 3) of fractionation are as follows. From elution with n-hexanelbenzene (3/1) was obtained a mixture (52.5 mg) of 2,4,6-tri-tert-butylphenol 5 and 2,6-di-tert-butylphenol 4, and elution with n-hexane/ benzene (1/1)yielded 2,4-di-tert-butylphenol3 (45.8 mg). Elution with benzene afforded 2-tert-butylphenol 1 (42.7 mg). The last fraction eluted by CH2C12was 4-tert-butylphenol2 (1.1mg). The data for 1-5 follow. 1: bp 220 "C; 'H NMR (CDCI,) 6 6.50-7.40 (m, 4 H), 4.90 (br, 1H), 1.37 (s, 9 H).18 2: bp 235 "C; 'H NMR (CDCl,) 6 6.67-7.28 (q,4 H), 4.75 (br, 1 H), 1.29 (s,9 H).l8 3: mp 57 "C; 'H NMR (CDCl,) 6 6.35-7.45 (m, 3 H), 4.60 (br, 1H), 1.39 (s,9 H), 1.28 (s,9H).I8 4: mp 37 "C; 'H NMR (CDC13)6 6.65-7.30 5: mp 131 "C; 'H NMR (m, 3 H), 5.12 (s, 1 H), 1.31 (s, 18 (CDC13) 6 7.20 (9, 2 H), 5.00 (9, 1H), 1.44 ( ~ , 1 H), 8 1.29 ( ~ , H)." 9 tert-Butylation of 1,2-, 1,3-,and 1,4-Dihydroxybenzene (6, 7, and 8) with the Use of S i 0 2 (Table 111). Reactions were carried out by two methods. Method A. To a mixture of the substrate (2 mmol) and Si02 (1g) in CH2C12(4 mL) was added 2 mmol of t-BuBr and the mixture was stirred for 24 h at 30 "C. S O 2was filtered off and washed thoroughly with diethyl ether. The washings and the filtrate were combined and the solvent was removed. After analysis by 'H N M R spectroscopy the raw product was fractionated by preparative thin-layer chromatography (Si02/Merck60 PF) using CH2C12as a developing solvent. From 6 (2 mmol) were obtained 12a (10 mg, 3%) and 12b (19.9 mg, 6%) and 152 mg of 6 was recovered. The data for 12a and 12b follow. 12s: mp 55 "C; 'H NMR (CDC13)6 6.60-6.90 (m, 3 H), 5.70 (br, 2 H), 1.36 (s,9 H).19 12b: mp 54 "C; 'H NMR (CDC13)6 6.95 (m, 1 H), 6.84 (m, 2 H), 5.20 (br 2 H), 1.21 (s, 9 H)." From 7 (2 mmol) was obtained 13a (29.9 mg, 19%) and 148 mg of 7 was recovered. The data for 13a follow. 13a: bp 140 "C (2 torr); 'H NMR (CDCl,) 6 6.20-7.10 (m, 3 H),5.80 (br, 2 H), 1.36 (s,9 H).20 From 8 (2 mmol) was obtained 14a (49.8 mg, 15%) and 142 mg of 8 was recovered. The data for 14a follow. 14a: mp 128 "C; 'H NMR (CDC1,) 6 6.80 (m, 1 H), 6.59 (m, 2 H), 5.70 (br, 2 H), 1.30 (s, 9 H).Is Method B. To a mixture of substrate (2 mmol), SiOz (1 g), and Na2C0, (9 mmol) in CC14 (7 mL) was added t-BuBr (6 mmol), and the mixture was stirred for 24 h at 70 "C. Si02was filtered off and washed thoroughly with diethyl ether. The washings were combined with the filtrate and the solvent was evaporated. The crude product was purified by recrystallization from cyclohexane to afford 12c (386 mg, 87%) from 6, 13b (377 mg, 85%) from 7, and 14b (408 mg, 92%) from 8. The data for 12c, 13b, and 14b follow. 12c: mp 99 "C; 'H NMR (CDCl,) 6 6.86 (d, 1 H), 6.68 (d, 1 H), 5.24 (br, 2 H), 1.39 (s, 9 H), 1.21 (s, 9 H).18 13b: mp 118 OC; 'H NMR (CDC13)6 7.15 (s, 1 H), 6.13 (s, 1 H), 5.05 (br, 2 H), 1.35 (s, 18 H).lS 14b: mp 219 "C; 'H NMR (CDCl,) 6 6.53 (s, 2 H), 6.40 (br, 2 H), 1.29 (s, 18 H).l8 (18) "Handbook of Chemistry and Physics", 52nd ed.; Chemical Rubber Co.: Cleveland, OH, 1971-1972. Pouched, C. J.; Campbell, J. R. "The Aldrich Library of NMR Spectra", Aldrich Chemical Co.: Milwaukee, WI. (19) Phillips Petroleum Co. U.S. Patent 2 544 818, 1945. (20) Chichibabin, A. C. R . Hebd. Seances Acad. Sci. 1934,198, 1239.
Kamitori e t al.
tert -Butylation of 4,4'-Dihydroxybiphenyl, 2-Naphthol, and Anisole (9,10, and 11) with the Use of SiOz (Table 111). A typical procedure is given below with the case of 9. To a mixture of 9 (372 mg, 2 mmol), Si02(1g), and Na2C0, (1.908 g, 18 mmol) in CC&(7 mL) was added t-BuBr (2.466 g, 18 mmol) and the whole mixture was stirred for 24 h at 70 "C. Si02was filtered off and washed thoroughly with diethyl ether. The washings and the filtrate were combined and the solvent was removed under vacuum. The raw product was analyzed by GC and 'H NMR spectroscopy. In the case of 10 and 11, the products were isolated by column chromatography on SOp. From 10 there was obtained 16 (252 mg, 63%, eluted by CH2Cl2/Eh0(3/2)) and from 11 138 mg (42%) of 17a (eluted by benzene) and 62 mg (19%) of 17b (eluted by n-hexanelbenzene (3/7)). In the case of 15 each product was separated by preparative thin-layer chromatography (Si02/Merck60 PF) using CH2C12as a developing solvent. From the least polar fraction was obtained 15d (57 mg, 7 % ) , from the second fraction 15c (78 mg, l l % ) , from the third fraction 15b (250 mg, 42%), and from the most polar fraction 15a (29 mg, 6%). The data for 15a-17b follow. 15a:%mp 153 "C; 'H NMR (CDC1,) 6 6.51-7.51 (m, 7 H), 4.84 (br, 2 H), 1.47 (s, 9 H). 15b: mp 181-183 "C; 'H NMR (CDCl,) 6 6.57-7.53 (m, 6 H), 4.79 (br, 2 H), 1.43 (5, 18 H).22 15c: mp 184-185 "C; 'H NMR (CDCl,) 6 6.52-7.54 (m, 5 H), 5.18 (br, 2 H), 1.49 (s,18 H), 1.46 (s,9 H).23 15d: mp 185 "C; 'H NMR (CDCl,) 6 7.23 (s, 4 H), 5.10 (br, 2 H), 1.45 (s, 36 H).24 16:21v25mp 112 "C; 'H NMR 6.90-7.87 (m, 6 H), 4.68 (br, 1 H), 1.38 (5, 9 H).25 17a: bp 223 "C; 'H NMR (CDCl,) 6 6.60-7.10 (q, 4 H), 3.63 (s, 3 H), 1.25 (s, 9 H).26 17b: mp 103 "C; 'H NMR (CDC13)6 6.60-7.20 (m, 4 H), 3.68 (s, 3 H), 1.36 (5, 9 H).27 General Procedure for Alkylation of 2,6-Dialkylphenol (18a and 18b) in the Presence of S i 0 2 (Table IV). To a mixture of 18a or 18b (2 mmol), Si02 (2 g), and Na2C03(6-18 mmol) in CCl, (7 mL) were added halides RX (4-12 mmol), and the mixture was stirred for 0.5-24 h at the prescribed temperatures. Si02was filtered off and washed with diethyl ether. The washings were combined with the filtrate and the solvent was removed. After preparative thin-layer chromatography (SO2/ Merck 60 PF) using benzene/CH2C12(9/1) as a developing solvent 21 (27 mg, 6%) and 22 (37@mg, 57%) were isolated. In the case of no. 6, recrystallization of crude products from CHC13afforded pure 24a (108 mg, 42%). In the case of no. 1, 2, 5 , and 7, recrystallization of the crude product from n-pentane yielded 19 (303 mg, 85%),20 (180 mg, 47%), and 24b (331 mg, 78%) and from CHCl, 24a (223 mg, 87%), respectively. In the case of no. 4, pure 23 (165 mg, 47%) was obtained by ball tube distillation (150 "C (10 torr)) of the crude product. The data for 19-25 follow. 19: mp 82 "C; 'H NMR (CDCI,) 6 6.99 (s, 2 H), 4.07 (br, 1 H), 2.24 (s, 6 H), 1.28 (s, 9 H).28 20:21mp 90 "C; 'H NMR (CDC1,) 6 6.90 (s, 2 H), 4.40 (br, 1 H), 2.30 (s, 6 H), 1.30 (s, 6 H), 1.29 (9, 2 H), 0.80 (t, 3 H). 21: mp 82-84 "C; 'H NMR (CDCl,) 6 6.75-7.10 (m, 6 H), 4.40 (br, 1H), 3.75 (s, 2 H), 2.30 (s, 3 H), 2.15 (s,6 H).29 22:21mp 111-113 "C; 'H NMR (CDCl,) 6 6.70-7.20 (m, 9 H), 4.50 (br, 1 H), 3.92 (s, 2 H), 3.29 (s, 2 H), 2.29 (s,6 H), 2.21 (s, 3 H), 2.10 (s,3 H). 23: bp 150 "C (10 torr); 'H NMR (CDCl,) 6 6.80 (s, 2 H), 5.30-5.60 (m, 2 H), 4.60 (br, 1 H), 3.20 (br, 2 H), 2.20 (s,6 H), 1.70 (br, 3 H).,O 24a: mp 175 O C ; 'H NMR (CDCl,) 6 6.75 (s, 4 H), 5.30 (br, 2 H), 3.65 (s, 1 H), 2.20 (s, 12 H).,' 24b: mp 154 "C; 'H NMR (CDCl,) 6 7.01 (s, 4 H), 5.01 (s,2 H), 3.85 (s,2 H), 1.43 (s, 36 H).29 25:32 'H NMR (CDCl,) 6 7.00 (s, 2 H), (21) Satisfactory analytical data (f0.4% for C, H) were reported for these compounds. (22) Tashiro, M.; Fukata, G. J. Org. Chem. 1977, 42, 428. (23) Tashiro, M.; Fukata, G. Org. Prep. Proced. Int. 1976, 8, 241. (24) Kharasch, M. S.; Joshi, B. S. J. Org. Chem. 1957, 22, 1435. (25) Buu-Hoi, N. P.; Le Bihan, H.; Binon, F.; Rayet, P. J. Org. Chem. 1950, 15, 1060. Layer, R. W. Tetrahedron Lett. 1974, 38, 3459. (26) Olson, W. T.;Hipsher, H. F.; Buess, C. M.; Coodman, I. A.; Hart, I.; L m n e k , J. H., Jr.; Gibbsons, L. C. J. Am. Chem. SOC. 1947,69,2541. (27) Stork, G.; White, W. N. J. Am. Chem. SOC.1956, 78, 4606. (28) "Atlas of Spectral Data and Phisical Constants of Organic Compounds", 2nd ed. Chemical Rubber Co.: Cleveland, OH, 1975. (29) Miller, B. J. Am. Chem. SOC.1974, 76, 7155. (30) Mervell, E. N.; Logan, A. V.; Friedman, L.; Ledeen, R. W. J. Am. Chem. SOC.1954, 76, 1922. (31) This compound was not isolated. (32) Auwers, K. Chem. Ber. 1907, 40, 2528.
J. Org. Chem. 1984,49,4165-4171 4.50 (s, 2 H), 4.20 (br, 1 H), 2.22 ( 8 , 6 H).33 General Procedure for tert -Butylation of Heterocyclic Aromatic Substances (Table V). To a mixture of thiophene (336 mg, 4 mmol), SiOz (1 g), and Na2C03(1.272 g, 12 mmol) in CC14 (4 mL) was added 12 mmol(l.644 g) of t-BuBr. The mixture was stirred for 40 h at 78 "C. The reactions of 2-methylthiophene, benzothiophene, and 1-methylindol were carried out quite similarly. The furan reaction was carried out a t 25 "C for 24 h and then a t 78 "C for another 24 h. In each case SiOz was filtered off and washed with CHzCl2thoroughly. The washings were combined with the filtrate and the solvent was removed. Crude materials were analyzed by GC and 'H NMR. Purification for microanalyses by ball tube distillation afforded 26 (768 mg, Sa%), 27 (376 mg, 61%), 28 (734 mg, 51%), 29 (539 mg, 78%), and 30 (374 mg, 50%). The data for 26-30 follow. 26: bp 120 "C (20 torr); 'H NMR (CDC13)6 6.45 (8, 2 H), 1.30 ( 8 , 18 H).% 27: bp 160 "C (20 torr); 'H NMR (CDC13)6 6.50 (9, 2 H), 2.42 (s, 3 H), 28: bD 80 "C (12 torr); 'H NMR (CDCl,) 6 5.77 1.32 (9. 9 (s,2 H), 1.23 (s, 18 H).$ 29 bp 150 "C (6 torr); 'H NMR lCDCl3) (33) Wakelman, M.; Robert, J. C.; Decodta, G.; Vilkas, M. Bull. SOC. Chim. Fr. 1973, 1179. (34) Kuta, M. W.; Corson, B. B. J . Am. Chem. Soc. 1948, 68, 1477. (35) Messina, N.; Brown, E. V. J. Am. Chem. SOC.1952, 74, 920.
4165
6 7.15-8.16 (m, 4 H), 7.06 (s, 1 H), 1.43 (9, 9 H).37 30: bp 170 "C (0.1 torr); 'H NMR (CDCl,) 6 6.83-7.90 (m, 4 H), 6.54 (s, 1 H), 3.60 (s, 3 H), 1.40 (8, 9 H).%
Registry No. 1,88-18-6;2,9864-4; 3,96-76-4; 4, 128-39-2;5, 732-26-3; 6, 120-80-9; 7, 108-46-3;8, 123-31-9;9, 92-88-6; 10, 135-19-3; 11,100-66-3; 12a, 4026-05-5; 12b,98-29-3;12c, 1020-31-1; 13a, 2206-50-0; 13b, 5374-06-1; 14a, 1948-33-0;14b, 88-58-4; 15a, 91798-62-8; 15b, 60803-40-9; 1 5 ~61514-62-3; , 15d, 128-38-1;16, 1081-32-9; 17a, 2944-48-1; 17b, 5396-38-3; Ha, 576-26-1; 19, 879-97-0; 20, 91798-63-9; 21, 55563-86-5; 22, 91798-64-0; 23, 21104-18-7; 24a, 5384-21-4; 24b, 118-82-1; 24c, 107-30-2; 25, 28193-66-0; 26, 4789-40-6; 27, 15146-95-9; 28, 1689-77-6; 29, 35181-78-3; 30,46270-99-9;C6H50H,108-95-2;SOz, 7631-86-9; A1203, 1344-28-1; t-BuBr, 507-19-7; CZH5(CHJzCBr,507-36-8; p-TolCH,Cl, 104-82-5;CH&HCH(CH,)Cl, 563-52-0;thiophene, 110-02-1;2-methylthiophene, 554-14-3; furan, 110-00-9;benzothiophene, 95-15-8; l-methylindole, 603-76-9. (36) Brown, W. H.; Wright, G. F. Can. J. Chem. 1957, 35, 236. (37) Cooper, J.; Scrowston, R. M. J. Chem. SOC.,Perkin Trans. 1 1972, 414. (38) Janetzky, E. F. J.; Lebret, M. C. Recl. Trav. Chim.Pays-Bas 1944, 63, 123.
Photochemical Transformations and Laser Flash Photolysis Studies of 1,4and 1,2-Epoxy Compounds Containing 1,2-Dibenzoylalkene Moieties' B. A. R. C. Murty,2aC. V. Kumar,2 V. Dabral,2a P. K.
and M. V. George*2
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India, and Radiation Laboratory and Department of Chemistry, University of Notre Dame, Notre Dame, Indiana 46556
Received February 14, 1984 Photochemical transformations of a few 1,4- and 1,a-epoxy ketones have been investigated. Irradiation of a benzene solution of 1 gave a mixture of 3 (32%) and dibenzoylacetylene(DBA, 6,13%), whereas the photolysis of 8 in methanol gave a mixture of the ester 12 (56%) and DBA (22%). Irradiation of 14 in benzene gave a mixture of the isomeric lactone 17 (25%), 1,3-diphenylisobenzofuran(20,20%), and o-dibenzoylbenzene(23,10% ). The photolysis of 24 in both benzene and methanol resulted in isomerization to the anthracene derivative 25 (6% and 20%). The same product (25,38%) was obtained in the thermolysis of 24. Plausible mechanisms for the formation of the various products have been discussed. Laser flash photolysis (337.1 nm) of 1,8, and 14 in benzene and methanol led to the observation of short-lived transient species, characterized by absorption maxima at 405-490 nm and by lifetimes (rT) in the range 0.4-2.0 ks. Pulse-radiolytic observation of the same transients under energy-transfer sensitization as well as detailed quenching studies using oxygen, di-tert-butylnitroxide, azulene, ferrocene, and p-carotene led to the assignments of the transients as triplets. The quantum yields of triplet formation (@T) under direct laser excitation were estimated to be high (0.50.74). Upon laser flash photolysis, 24 produced the anthracene derivative 25 nearly within the laser pulse; the intermediacy of a triplet with 7T -7 ns and aT 1was established in this case by quenching studies involving 1-methylnaphthaleneand 2,5-dimethyl-2,4-hexadiene.
-
Introduction Phototransformations of several 1,&epoxy compounds containing ester substituents have been reported earlier.Thus, 7-oxanorbornadienes on direct irradiation give oxaquadricyclanes, presumably through a [ r 2 s + r 2 s ] addition. In contrast, the sensitized irradiations of oxaquadricyclaneslead to 6-hydroxyfulvenes. Similarly, direct irradiation of benzoxanorbornadienes gives benzoxepine (1) Document No. NDRL-2553 from the Notre Dame Radiation Laboratory. (2) (a) Indian Institute of Technology. (b) University of Notre Dame. (3) Payo, E.; Cortes, L.; Mantecon, J.; Rivas, C.; de Pinto, G.Tetrahedron Lett. 1967, 2415-2417. (4) Prinzbach, H. Pure Appl. Chem. 1968, 16, 17-46. (5) Prinzbach, H.; Argiielles, M.; Druckrey, E. Angew. Chem. Int. Ed. Engl. 1966, 5, 1039. (6) Prinzbach, H.; Vogel, P.; Auge, W. Chimia 1967, 21, 469-472; Chem. Abstr. 1968,68, 10495711. (7) Prinzbach, H.; Vogel, P. Helu. Chim. Acta 1969, 52, 44-45. (8) Eberbach, W.; Argiielles, M.; Achenbach, H.; Druckery, E.; Prinzbach, H. Helu. Chim.Acta 1971,54, 2579-2600.
derivatives,"" whereas, indene derivatives have been isolated in the sensitized irradiation of certain benzoxanorbornadienes." Photochemical transformations of several 1,2-epoxy compounds containing carbonyl substituents have been investigated in detail.12-16 An interesting case is that of (9) Ziegler, G. R.; Hammond, G. S. J . Am. Chem. SOC.1968, 90, 513-514. (10) Ziegler, G. R. J . Am. Chem. SOC.1969, 91, 446-449. (11) Matheson, R. A. F.; McCullough, A. W.; McInnes, A. G.; Smith, D. G. Can. J. Chem. 1977,55, 1422-1431. (12) Venkataramani, P. S.; Saxena, N. K.; Srinivasan, R.; Ors, J. J . Org. Chem. 1976,41, 2784-2785. (13) Lewars, E. G.; Morrison, G. Can. J. Chem. 1977, 55, 966-974. (14) Bertoniere, N. R.; Griffin, G. W. "Organic Photochemistry"; Chapman, 0. L., Ed.; Marcel Dekker: New York, 1973; Vol. 3, pp 115-195. (15) Jeger, 0.; Schaffner, K.; Wehrli, H. Pure Appl. Chem. 1964, 9, 555-565. (16) Padwa, A. "Organic Photochemistry"; Chapman, 0. L., Ed.; Marcel Dekker: New York, 1971; Vol. 1, pp 91-126.
0022-3263/84/1949-4165$01.50/0 0 1984 American Chemical Society
