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Oxidation of Hydrocarbons with Benzyl(triethyl)ammonium Permanganate.

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t - C H~
fC
&-& - &
%eN-t-CdHB
R
R'
:C=N;C&
' x /
' x /
(1)
\
x
E
/
(4)
(3)
in the dark. After removal of all volatile components in a
rotary evaporator at 30°C the crude oil is separated on a
silica gel medium-pressure column with anhydrous petroleum
ether (60-70°C)/ether (2: 1). The main fraction (IR band
at 2060cm-I) is evaporated in a rotary evaporator; the resulting colorless oil crystallizes. ( 4 a ) , yield after recrystallization
from anhydrous petroleum ether (60--70"C)/ether (1 : 1) 1.6g
(82 %), melts at 146--148"C.
Received: September 4, 1978 [Z I16 IE]
German version: Angew. Chem. 91, 62(1979)
G. Egc, 8. Hahfi, Justus Liebigs Ann. Chem. 763, 39 (1972); cf. also
B. Sclirudcr, Tetrahedron Lett. 1971, 2993.
[2] W. J. MiddLrori, J. Org. Chem. 30, 1402 (1965); N . Obarn. 7: Tukixico.
Tetrahedron Lett. 1969, 3403.
[3] H. J. Dilliiiger, G. Feiigler, D. Scl~i~~iiuii~i,
E. Wimrfcldr, Tetrahedron
30.2553( 1974);7: Tnkizuwa, N.Obotu, Y.Sirzvki, 7: Yn~iugidu,Tetrahedron
Lett. 1969, 3407; A. Krebs, H. Kiiiiliiig, Angew. Chem. 83, 401, 540
(1971); Angew. Chem. Int. Ed. Engl. 10, 409, 509 (1971).
[I]
(5)
1
Table 1. Data for the vinyl ketenimines ( 4 n ) - ( 4 e ) .
X
R
M.p. ["C]
[%]
U V (CH2CIz)
imaX
[nm] (I:)
IR
[cm-'1
'H-NMR (60 MHz, &values;
in
CDC12/TMS
82
326 (8000). 251 (21 200)
2060
391.1 783
1.16 (s, 9H, t-C4H9),3.50 (s, 3H, OCH,),
3.71 (s. 3H, OCH,), 6.4-8.1 (m, IOH, aromat. H) 391.1767
62
372 (8100). 319 (6500).
303 (7600). 264 (373001,
255 sh (30900), 244 (28400)
2060
389.1627
1.32 (s, 9H, r-CjH9). 3.77 (s, 3H, OCH,),
3.95 (s, 3H. OCH,), 7.1-7.9 (m, 8H, aromat. H) 389.1642
Yield
H MS (iit/e)
calc.
obs.
n
H. H
COOCH,
146-148
b
Direct
linkage
COOCH,
30-35
c
C(CHj)z
COOCHi
130-131
63
321 (8600). 266 (8600)
2050
1.33 (s, 9H, I - C ~ H ~1.67
) , (s, 6H, C(CH,)z),
3.47 (s. 3H, OCH,), 3.58 (s, 3H, OCHj),
7.0-7.8 (m, 8 H, aromat. H)
d
CHz-CHz
COOCH,
92-94
53
312 (5600). 260 (19100)
2060
1.27 (s, 9H. f-C4H9),2.4-3.8 (m, 4H, CHzCHz), 417.1940
3.46 (s, 3H, OCH,), 3.56 (s, 3H, OCH,),
417.1929
6.9-7.5 (m, 8H, aromat. H)
e
Direct
linkage
H
oil [b]
43
-
2025
I .34 (s, 9H, r-C4H9),3.90 (s, 3 H, OCH,),
6.9-7.9 (m. 8H. aromat. H), 8.0 (s, 1 H, olefin. H)
[a]
43 I .2096
43 I .2099
[a] Yellow glassy mass. [b] Not pure.
The reaction is initiated by nucleophilic attack of the tertbutyl isocyanide ( 2 ) at the reactive double bond of the cyclopropene ( 1 ) . The dipolar compound (3) is formed, in which
the negative charge on the cyclopropane ring is stabilized
by the electron acceptor R. Subsequent opening of the cyclopropane ring in (3) leads to the conjugated ketenimine ( 4 ) .
This ring cleavage opens up a new entry to vinylketenimines
( 4 ) , only one example of which has hitherto been described
in the literature[''.
The constitutionally specific ring-opening of the adduct
(3) rules out intermediary formation of a bicyclobutanone
imine ( 5 ) : the unsymmetrically substituted (3 e ) affords exclusively ( 4 e ) . The structure of ( 4 e ) follows from the long-wave
position of the ketenimine band at 2025cm-' [ ( 4 a ) - ( 4 d ) r
2050 to 2060cm- '1 and thedownfield position of the 'H-NMR
signal of the COOCH3 group at 6=3.90 [ ( 4 b ) : 6=3.95 and
3.771.
Experimental
Synthesis of ( 4 a ) : ( I a ) [ ' ] (1.54g, 5mmol) is dissolved in
anhydrous benzene (30ml), treated with 0.42g (5mmol) (2)
and allowed to stand for three days at room temperature
68
[4] ( l a ) see [I]; ( I b ) : G. Ege, Tetrahedron Lett. 1963, 1667; (fc). ( I d ) :
K. Gilberf. projected Dissertation, Universitlt Heidelberg 1979; ( 1 E ) :
H. Rciiiilinger, Chem. Ber. 100. 3097 (1967).
[5] ( 6 ) : yellow crystals, m.p. 187-189°C (CH30H); UV (CH2C12):412
(12800), 287 (22600). 272sh (34400). 264 (35600). 250 (41000) nm; IR
(KBr): 3240 (NH). 1715, 1645, 1600cm-' (enamino ester); 'H-NMR
(90 MHz, CDCI,): S = 1.37 (s, 9H, f-C4H9). 3.64 (s, 3H. OCH,). 3.68
(s, 3H. OCH,), 3.90 (s, 3H, OCH3), 7.0-7.7 (m, 8H, aromat. H), 9.64
(s, I H, NH. exchangeable).
[6] E . Sofiueutrs, L. Gkosez, J. Am. Chem. SOC.95, 5417 (1973); regarding
a dienylketenimine cr. H. H. Eckhnrdf, H . Persf, Angew. Chem. YO,
497 (1978);Angew. Chem. Int. Ed. Engl. 17, 465 (1978).
Oxidation of Hydrocarbons with
Benzyl(triethy1)ammonium Permanganate
By H.-Jiirgen Schmidt and Hans J. Schafer1.1
C H bonds can be oxidized with permanganate ions; however, the use of this method is greatly ,restricted by the insolubility of the alkanes in aqueous solution['! A further disad-
['I
Prof. Dr. H. J. Schlfer, Dipl.-Chem. H.J. Schmidt
Organisch-chemisches lnstitut der Universitlt
Orleans-Ring 23, D-4400 Munster (Germany)
Aiigew. C1iein. lift. Ed. Eiigl. 111 (1979) No. 1
vantage is that alkylarenes are degraded to arenecarboxylic
acids[']. The advantages of oxidation in organic solvents have
hitherto been exploited only in isolated cases. Olefins can
be cleaved to carboxylic acids with potassium permanganate
in benzene. if the potassium ion is complexed with a crown
etherr3].In pyridine, alcohols and aldehydes can be oxidized
to carboxylic acids with tetrabutylammonium permanganate[4'.
We report here on the oxidation of alkanes with benzyl(triethy1)arnmonium permanganate (1 ) in dichloromethane
or glacial acetic acid (Table 1). ( 1 ) precipitates as a violet
salt on treatment of an aqueous solution of the corresponding
chloride with potassium permanganate[? It is thermally stable
at 100°C. resistant to shock, and readily soluble in dichloromethane and glacial acetic acid (0.3-0.5mol/l), in which it
is relatively stable.
Table I . Product5 of the oxidation of alkanes with henzyl(triethyl)ammonium
permanganate ( I ).
Alkanc
Oxidation products, Yields [a]
Cumene 1 2 ) [b]
2-PhenyI-2-propano1, 28 ",, (98 X ) , acetophenone, I
2-Phenyl-2-butanoI. 12 "4 (61 %,), dcetophenone, 1 "G: propiophenone. 19": ( I methyl-I-phenylpropyl)acetate,2"; ( I 2 ");,
Isobutyrophenone, 26 Yo (51
2-methyl-lphenyl-2-propanol,
3 yo: (3.r-dimethylphenethy1)acetate. 20 'yo (
ri-Butyrophenone, 44 % (
tyl)acetate, 26 (37 %)
3-Pentanone. 12 % (25
tanone, 13 (25 "/;):3-ethyl-3-pentanol, 12 ?lo
(24 %); (1,l-diethylpropy1)aceta
I-Methylcyclohexanol, 23 ":,( 7
ylcyclohexanone. 3 "4
rrrrr1s-9-Decalol. I 1 "/#',(37
rrurwl -decalone, 13 % (43 "i);truris-2-decalone, 3 ",A
<.i.s-9-Decalol.33 7" (67 %)
s"(
-Butylbentene ( 3 J [c]
lsohtitylhenzene ( 4 ) [d
11-Butylbenzene ( S i [e]
3-Ethylpentane (61 [f]
Methylcyclohexane ( 7 ) g]
rruns-Decalin ( X i [h]
cis-Decalin ( Y ) [h]
[a] Chromatographically determined yields, based on original amount of
alkane and (in brackets) on consumed alkane. [b] 50mmol (2). 52mmol
( I ) . 6mmol pyridinr. 3 d at 40°C in CH2C12. [c] 50mmol (31, 50mmol
(1),2dat40"CingIacialaceticacid.[d] 5 0 m m o l ( 4 ) , IOmmol ( I ) , l00mrnol
KMnOl. 4 d at 30°C in glacial acetic acid. [el As in [d] hut only 2d.
[g As in [d] bur at 50°C. [g] As in [d] hut 2d at 60°C. [h] as in [d]
hut only 3 d.
Benzylic methylene groups [ ( 4 ) , ( 5 ) ] are oxidized to the
ketone; cleavage to benzoic acid is suppressed. Tertiary benzylic CH-groups [(2), ( 3 ) ] are smoothly transformed into tertiary alcohols. Some aliphatic methine groups [ ( 4 ) , (6)-(9)]
require higher reaction temperatures and activation of the
permanganate by glacial acetic acid as solvent, whereupon
the alcohol formed is partially dehydrated and/or secondary
methylene groups are also oxidized. Hydroxylation of the
decalins [ ( 8 ) , (911 proceeds stereospecifically with retention
of configuration.
In the oxidation of alkanes with ( I ) the yields obtained
are not as high as those achieved by dry ozonolysis[61;however,
the former method appears to be advantageous for the oxygenation of alkylarenes, which are degraded to alkylcarboxylic
acids by ozone['].
Exprrimenfal
Preparation of benzyl(triethy1)ammonium permanganate
( I ) [ 5 1 : A solution of benzyl(triethy1)ammonium chloride
(227.8 g, 1.00mol) in 200ml water is added dropwise and
slowly to a solution of potassium permanganate (1 58.0g,
1.00 mol) in 4.7 1 water. The violet crystals are recovered by
filtration and dried at 4OaC/0.2 torr. Yield of ( 1 ) 294.8g
(0.947 mol, 95 XI; over 99 '%I pure (iodometrically)); m. p.
(decomp.) 127-1 29°C.
Received: November 6, 1978 [Z 123a IE]
German version: Angew. Chem. YI. 77 (1979)
D. G . Lee in R. L. A i r y u s t i w Oxidation. Marcel Dekker, New York
1969. Val. 1. p. 3.
R. S r r i w r r in K . 5.Wibrrg. Oxidation in Organic Chemistry. Academic
Press, New York 1965, Part A, p. 39; C. F . Cullia, J . W Ludhury.
J. Chem. Soc. 1955, 2850.
D. J . Sum, H . E. Sirnmnrrs, J. Am. Chem. Soc. 94. 4024 (1972); G. W
Gokrl, H . D. Dvrsr, Synthesis 1976. 168.
7: Sulu, M . K Surgerlr. J. Chem. Soc. Chem. Commun. IY78, 253.
1 Cluirsseii, Diplomarbeit, UniversitPt Munster 1977.
Z . Cohen, E. Keiriun. Y .Uuzur, 7: H . Vrrrkori?., J. Org. Chem. 4 0 . 2141
( I 975).
H . Kleiri, A . Stt!i!irnefz, Tetrahedron Lett. 1975, 4249.
[I]
[2]
[3]
[4]
[5]
[6]
[7]
Oxidation of Ethers with Benzyl(triethy1)arnmonium
Permanganate
By H.-Jiirgen Schmidt and Huns J . Schufer[*]
Ruthenium tetraoxide has long been known to be a particularly suitable reagent for the oxidation of alkyl ethers"]. Other
oxidizing agents have also been used. For example, chromium
trioxide''] and trichloroisocyanuric acidr3]oxidize ethers to
esters and lactones, respectively. Reaction with
uranium hexaflu~ride[~],
lead tetraacetatec6I or
as
well as anodic oxidation[*], leads via oxidative cleavage of
the ethers to carboxylic acids, ketones and alcohols. Ruthenium tetroxide is, of course. only suitable for the oxidation
of dialkyl ethers, since aryl groups are oxidatively degraded.
This disadvantage is overcome on oxidation with benzyl(triethy1)ammonium permanganate ( I ),which oxidizes ethers cleanly
and chemoselectively to esters (Table 1).
Table I. Products of the oxidation of ethers with benzyl(triethy1)ammonium
perrnanganate ( I ).
Ether
Oxidation products. Yields [a]
Dibutyl ether ( 2 ) [b]
Dibenzyl ether ( 3 ) [c]
Butyl hutyrate, 58 y,, (80 %)
Benzyl benzoate, 80 ',<, (84
methylene dibenzoate, X"%
Butyl benzoate, 90 '?
Methyl butyrate, 23
Benzyl butyl ether ( 4 ) [d]
Butyl methyl ether (5) [el
Methyl octyl ether (6)
Benzyl (I-ethylpropyl) ether ( 7 ) [g]
[fl
Benzyl methyl ether ( X I [g]
(85 'yo)
Methyl benzoate. 83 '4(84 "")
Bntyl (I-ethylpropyl) ether ( 9 ) [h]
Benzyl (I-phenylethyl) ether ( I O ) [i]
Benzyl phenyl ether ( I I ) h]
Butyl (I-phenylethyl) ether ( 1 2 ) [k]
Butyl phenyl ether ( 1 3 ) [fl
(83 "~:,); acetophenone. 6 'k
Phenyl benzoate, 42 '',<,(94 "6)
Acetophenone,
38",,
(67
(I-phenylethyl)hutyrate.3~~,:
butyl
benzoate, 2 "<,
Phenyl butyrate. I I ",,, (92 "<,)
[a] Yields based on initial amount o l ether and (in brackets) amounts of
ether consumed: determined by gas-chromatography. [h] 30 mmol ( 2 ) ,
IOmmol ( I ) , 50nimol KMnO, in lO0mi H 2 0 , IOOml CH2CI2, 14d at
30°C. [c] 30mmol ( 3 ) . 60mmol ( I ) in Ch2C12. 6 d at - 5 t o 20°C. [d]
As in [c], but 8 d at 0°C. [el As in [b], hut IOd at 42°C. [f] As in [h].
hut at 42°C. [g] A5 in [ c ] , hut 7 d at -5°C. [h] As in [h]. but 30 to
42°C. [i] As in [ c ] . but 9 d at 5°C. b] As in [c], but Yd a t 0°C [k]
As i n [b]. hut 8 d at 25°C.
_ _
[*I
-
Pro[. Dr. H. J. Schlfer, DipLChem. H.-J. Schmidt
Organisch-Chernisches lnstitut der UniversitBt
OrIednS-Ring 23, D-4400 Munster (Germany)
69
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