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Hydroxylation of Acyclic Alkanes by O(3P) Comparison of Ozone and O(3P).

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respectively /4/. Larger yields of the methyl cleaved ketone, Z-methyl-
Dieses Manuskript ist
zu zitieren als
Angew. Chem. Suppl.
This manuscript is
to be cited as
Angew. Chem. Suppl.
1982,606-615
1982,606-615
These ketones amounted to a very large fraction of the products (between
Comparison of Ozone and 0( 3 P )
4 2 and 72%).
**
Since the undersirable C-C cleavage products were found only in small
have recently found /I/ that methylcycloalkanes could be oxidized.
in the liquid phase, with O ( 3 P ) atoms formed by low pressure microwave
flow systems /2/.
rendering ozonation unsuitable as a method of hydroxylation
of acyclic hydrocarbons (Table I).
Elarar Zadok and Yehuda MaZUr *
a
(Table I).
dramatic increase in the yield of ketones formed by cleavage of
C-C bonds was observed by 11s in the ozonation of acyclic alkanes 161.
Hyaroxylatlon of Acyclic Alkanes by O(3Pl
discharge o f mixture of C02 and He in
cyclohexanes / 5 / .
A
0 Verlag Chemie GmbH. D-6940 Weinheim. 1982
0721-4227/82/0404-0606S02.50/0
We
cyclohexanone, were obtained on ozonation of 1,Z-cis
- and --dimethyl-
The products
are tertiary cyclohexanols, accompanied by secondary cyclohexanols,
cyclohexanones and epoxycyclohexanes.This method of hydroxylation is
comparable to ozonation, which alzo results in tertiary alcohols /3/.
amounts in the 0(3P) oxidations of methylcyclohexanes /l/, we also
expected the respective ketones not to be formed extensively in the
oxidations of aliphatic hydrocarbons. Thus, reaction of 2.3-dimethylbutane with O(3P)
atoms in neat liquid at -80" using the method described
previously / 2 / resulted in 2,3-dimethylbutan-Z-o1 (64%) and 1,2-epoxy2,3-dimethylbutane (33%) (Scheme I).
Scheme
One of the significant differences between the two methods is that ketones
I
derived from C-CH? bond cleavage in the O3 reactions were obtained only
in minute amounts in the oxidation with O(3P)
Li A l HL,
atoms. Thus, ozonation of
t
I
methylcyclohexane led to ca. 5% of cyclohexanane, while that of 1,4-&
#OH
+
03= &(OH
+
and e-dimethylcyclohexanes gave 7 and 11% of 4-methylcyclohexanone,
>--(
*Prof. Dr. Yehuda Maiur; Elazar Zadok, M.Sc. Department of Organic
4
+
Chemistry, The Wcizmann Institute of Science, Rehovot, Israel.
On the other hand, reaction of the same hydrocarbon with O3 / 6 / gave
**This work was supported by the U.S.A.-Israel Binational Science
only 35% of the tertiary alcohol and 65% of acetone and isopropylmethyl
Foundation, Jerusalem.
ketone, the C-C bond cleavage products (Scheme I, Table I)
- 606 -
- 608 -
Table I
Ketones formed by C-C bond cleavage from ozonation
f saturated hydrocarbons
Cleaved productsa
Substrate
Q
5'
Q
0
b
ref.
H
64 (97)
4
7-
55
'y'
11
this
work
Ho28
Ivl
4
3
8
37
tertiary
alcohols"
substrate
16
H
Product distribution in the reaction of O(3P)
with acyclic hydrocarbons
4
7
16
AA
Table I 1
9;
An
sec. and prim
alcohols +
ketones
epoxides
C-C
cleavage
products
2
34
(73)
21
20
4
52
(75)
13
24
12
45
(82)
40
51 (67)
17
A
1
9
a)in paranthesis: relative yields after reduction of reaction mixture
with lithium aluminum hydride.
'y'
L
3"
of the total reaction products.
- 607 -
- 609 -
Table 111
Ratios of tertiary
YS.
In Table I1 we have summarized the results of O(3P) oxiddtion of
secondary oxidation products nnd
five ;acyclic hydrocarbons, which shows that cleaved ketones were datpcted
relative reactivities (per H) in thp reactions of O 3 and
O(3P) with cyclohexane derivatives.
only in two cases and then i n low relativa yields. The major products of
these oxidations were tertiary alcohols and tertiary epoxides. Since
lithium aluminium hydridc reduction of these epoxides leads mainly to
the same tertiary alcohols, the reduction of the total mixture of products
resulted in a comparatively high yie?d of these alcohols (Tahle 11).
O(3P) oxidation 1s therefore a convenient method for the preparative
conversions of acyclic saturated hydrocarbons to tertiary alcohols.
Aiming to clarify the differences between the two reagents, we have
compared the product distributions in the reactions with 2 and
=-
1,Z-dimethylcyclolirxanes. Table Ill shows the ratios of tertiary v s .
secondary oxidation products formed in the reactions with 0, snd O(3P)
atoms, respectively. These results indicate similar preferences of these
two reagents f o r the tertiary positions.
In Table IV we have compared the distribution of the epimeric
tertiary alcohols formed in these reactions. It may be seen that although
both reagents result in high retention of configuration, they differ in
aperformed by adsorbing the substrate on silica gel (1% w/w)
and passing
selectivity towards axial and equatorial H-atoms. Assuming the same
O3 (35 in 02)at -78* for 0.5-2 hrs.
bperformed by passing O(3P)
atoms produced by microwave discharge of
He/C02 mixture ( l 0 : l ) at 4 torr. on neat liquids at -40"- -78" for
1-2 hrs.
reactivity o f the tert-axial H-atoms in both epimeric hydrocarbons, we
have calculated the relative reactivity of O 3 and O(3P) atoms for
equatorial vs. axial H-atoms to he 7 , 3 : 1 and 1,2:1 respectively /7/.
- 610 -
- 612 -
'Thus C 3 has much higher steric demandsLhanO(3P)
Table IV
Distribution of tertiary alcohols from O(3P) oxidation
and =-I,?
dimethylcyclohexanes
and ozonation of
atoms, in accord with
the mechanism proposed f o r these reactions.
The mechanism for the oxidation of saturated hydrocarbons with O(3P)
atoms involves 11-abstraction /8/ to form an alkyl and Ofi radical pair
/1/
0 reaction products
substrate
b
0.'
I : I mixturea
b4.H
96
WH
4
(Scheme 11).
Combination of the radicals in a solvent cage /1,9/
0(3P) reaction products
6 . H
90
Scheme II
WH
10
leads to alcohols. Part of the radicals disproportionate inside the cage
to give H 2 0 and olefins which, on reaction with O?P)
atoms, form
epoxides. The escape of alkyl radicals from the solvent cage leads t o
1
'
.99
<2
.98
olefins, which are also converted to cpoxides 111.
The rate limiting step in this reaction is the abstraction process,
81
19
53
47
which occurs when an O(3P) atom is calinear with the C-H bond
m/.
This
colinearity may explain the comparatively smaller steric demands observed
in the O(3P) reactions.
We have suggested that oionntion of saturated hydrocarbons proceeds
through reversible formation of a dipolar complex, /ll/, whose
decomposition involves a bulky transitions state having ionic character,
which leads either to oxygen insertion into C-H bonds, or O3 insertion
to C-C bonds (Scheme 111). The former pathway leads to alcohols and the
latter to trioxides which are cleaved to ketones /3,11/. It thus appears
that in the dipolar transition state for the reaction of O3 with
hydrocarbons there exists relatively larger availability of tertiary C-C
- 611 -
- 613 -
Scheme
a
,
~
5
trrt;.iry
.
(.-I1 bonds
one,.
11115
le;id-
tn
I
.
Dieses Manuskript ist
zu zitieren als
Angew. Chem. Suppl.
This manuscript is
to be cited as
Angew. Chem. Suppl.
7982,616-621
7982,616-621
0 Verlag Chemie GmbH, D-6940 Weinheim, 1982
0721 -4227/82/0404-0654S02.50/0
the acyclic hydrocarbons than in the cyclic
preferential attack of O3 on tertiary C-C bonds in
10
Hetero-Diels-Alder-Reaktionen
zur Synrtese von
.~
~~
the . r < v r l i c conpounds and the formation of cleaved products.
___
yoromboxan-Zwischenstu<en _ ++
_
Procedure.
Richard R. Schnidt
Reaction of 3 rth\ I-pmtane with ground state oxygen atoms:
p a s s e d through
suhstr:ite.Onc
I
r h o neck flask containing 2 g. of magnetically stirred
i l r c l of
the flask was connected to the vacuum pump through
d r y - i L c - a c e m n e condenser and the other to the microwave generator
ikiv:! W - 2 ,
3
hrs.
at
24SO MIlz,
100 watt) through a
gas
discharge cavlty. After
-78"t'.t h e reaction mixture was reduced urino lithium aluminium
hydrjcle ~n rrh?i
'The products were separated an silica gel column to
g i v e 1.li R. of i t.thyl-3-pentano1,
0.2 g. of 3
ethyl 2-pcntanol and
2. Zadol.. I:.;
sem Wege zuqanglich sein sollten /2/. ?n dieser Synthesekonzept sind die Verbindungen 1 und
2
wichtige Zielmolekule.
2
durch Hetero-Diels-
Y.;
3
mit einem Substituenten R ' aus
zwei C-Atomen, der die stereospezifische EinfShrung der Hy-
Mazur, Y.; J. h e r . Chem. Sac.,
3. Cohcn, Z.; Kr~nan,E.; Maarur,
(19751,2142.
"2,
(1980) 6369.
Varkony, T.H.; J . Ora. Chem., ",
F., Ph.D. Thesis, Feinberg tiraduate School, The Weizmann
Institute of Science, Rehovot, Israel (19?7).
4 . Keinnn,
+
Prof. Dr. R.R. Schnidt, Dr. W. Abele
Fakultat fSr Chemie der Universitat. Postfac!, 5 5 6 0 ,
D-7750 Konstanz 1
++ De novo-Synthese von Kohlenhydraten und verwzndten Natur-
5 . 0zon:ition on S i O z of ~ - 1 , 2 - d i ~ e t h y l c y c l u h e x a n led
e to trans-1,2dimcrhylcyclohcxanol (62%) cis-l,2-dimethylcyclohexanol (o.s\),
dimethylcyi.lol,Pxanoncs (21%!=d
2- nethylcyclohexanone (16%) and that
of c i i - 1 , 2 - d i m r t h y l c y c l o h e x a n e to the Same compounds in 2.5,69, 12,
.
stoffen, 8 . Mitteilung. Diese Arbeit wurde Y o n der Deutschen Forschungsgemeinschaft und vom Fonds c'er Chemischen
Industrie un,terstutzt. - 7. Mitteilung: /1C/.
- 614 -
- 616 -
Ihamrcbpectiualy.
6. lal, 11.; Keinaii, 1.; Mamr, Y.; J. Am. Chem.
SOC.,
0'.
(1978) 5 0 2 .
7. Similar rcsultr were obtained hy Hamilton, G . A . ; Ribner, B . S . ;
Hellmnn, T.M., Adv. Chem. Ser.,
77, (1968), 15, for the ozonation
1,2-dimethyl cyclzexanes in solution.
of
and
a
8.
z e i n t , daR
?
lie kohlenhydratanalogen Thromboxane (wie TXB2, auch auf die-
a ) fin l-Alkoxy-1,3-dien
Y., in publxcation.
Amar, n.;
modifiiierten Kohlenhydraten sind /l/. Schema
Alder-Reaktion sind folgende Verbindungen erforderlich:
Hefererrcch and Note\
~1. Zadol, k , , hla:ur.
Hetero-Diels-Alder-Reaktionen fiihren z u reaktiven Pseudoqlycalen, die niitzliche Zwischenstufen fur kurze Cynthesen von
Zum Aufbau der Pseudoglycal-Struktur
0.6 y . of st:irting material.
and
.
und Wolfgan? Abele
flow ot' C%J2and He (0.7 L/min, 1:12 ratio) a t 2 tort-. was
A steady
,I
+
Pnraslievapoulos, ti.; Cvetanovic, R . J . : J . Phys. Chem.,
2598; Wright, I ' . J . ; J. Chem. Phys., 2, (1963). 950.
g,
z
1
(1977),
Schema 1
9. tlori, A . ; 'Takarnuku,S.; Sakurai, H.; J. Org. Chen., 4 1 , (19721,
2318.
droxygruppe an C-3 und anschliefiend die Anknupfunrj der Sex10 Andersen, I'.;Lmz.
11
A.C.;
J . Chem. Phys., 12 (1980) 5842 and 5851.
Varkony. T.H.; Pass. S.; Mazur, Y . ; J . Chem. Soc., Chem. Comun.,
(1974), 4 3 7 ; C f : Olnh, G . A . : Parker, D.G.; Yoneda, N.; Angew.*.
Int. td. Eng.,9 0 11978) 962; Angew. Chem. Int. Ed. Engl. 22
(1978) 909.
tenkette ermoglicht,
b ) eine Carbonylverbindung $ mit einem
Substituenten R 2 , der die Dienophilie erhbht upd c'ie Ankniipfung der zweiten Seitenkette ermbglicht. Dle elektronische
Polarisation und HOMO/LUMO-Betrachtunqen /3/ an 2 und
4
und
Reaktionen des l-Methoxy-l,3-butadiens mrt CarbonylverbindunReceived August 6 , 1981 / Z 43
S/
gen / 4 /
sprechen fiir eine regiospezifische Bildung des erwar-
teten Adduktes.
Die Synthese wurde mit dern (Z,E)-l-Methoxg-l.3-hexadien
2 /5/,
das an C-4 den erforderlichen funktionellen C2-Substituenten
enthalt, und dem (-1-Glyoxylsaure-menthylester
6
als reakti-
vem Dienophil begonnen. Cycloadditionen unter verschiedenen
Bedingungen lieferten (ohne asymmetrische Induktionl ein Gemisch der Pseudoglycaluronate
8, 9
und _10, die saulenchroma-
tographisch (Silicagel), Elutionsmittel: Petrolether/Essigester = 4:l) bequem getrennt werden konnten. Alkoxydecarbonylierung des Mesoxals3ureester-Adduktes
7
/5/
fuhrte eben-
falls in guter Ausbeute zu einem 1:1-Gemisch aus
2
und
9. 9
wurde durch Bortrifluoridetherat-Katalyse quantitativ in das
- 615 -
- 617 -
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