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Hydroxylation of Acyclic Alkanes by Oxygen Atoms O(3P)ЦComparison of Ozone and O(3P) Oxidations of Alkanes.

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anomer 10 in quantitative yield. The higher thermodynamic stability of 10 is due to the anomeric and allylic effects['], which are effective in the OH5 conformation of
lo[''. The compounds 9 and 10 have the necessary relative
stereochemistry at C-4 and C-5. After conversion['] into the
lactone 1 1 , reduction with equimolar amounts of diisobutylaluminum hydride (DIBAH) at -70°C affords the lactol. After reaction with terf-butyl(dimethyl)silyl chloride
(TBDMS-CI), the carboxylic acid 13 is obtained by ester
hydrolysis, and the aldehyde 14-an analogue of 1 -by
repeated reduction with DIBAH. The compounds 11, 13
and, in particular, 14 are valuable intermediates for
thromboxane syntheses.
Received: July 20, 1981 [Z 41 IE]
German version: Angew. Chem. 94 (1982) 298
The full manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 616-621
111 a) R. R. Schmidt, R. Angerbauer, Angew.
Chem. 89 (1977) 822: Angew.
Chem. I n t . Ed. Engl. 16 (1977) 783; b) R. R. Schmidt, R. Angerbauer,
Carbohydr. Res. 72 (1979) 272; ibid. 89 (1981) 159, 193: c) R. R. Schmidt,
A. Wagner, Synrhesis 1981. 272.
[ S ] W. Abele, R. R. Schmidt, unpublished results; W. Abele, Diplomarbeit
and Dissertation, Universitat Konstanz 1978 and 198 I , respectively.
[6] See [Ib] and references cited therein.
[7] "H, conformation was also observed in the pseudoglycaluronates 8 and
Table 2. Product distribution [%] in the reaction of O('P) with acyclic hydrocarbons.
Substrate
)-(
3^
'-f-'
&
Tertiary
alcohols
[a1
Secondary and
primary alcohols
+ketones
Epoxides
Ketones
(by C-C
cleavage) [b]
-
64 (97)
2
34
55 (73)
52 (75)
21
13
20
24
45 (82)
15
40
-
(57)
51 (67)
32
17
-
(771
(65)
4 (42)
12 (50)
[a] In parenthesis: relative yields after reduction of reaction mixture with lithium aluminium hydride. [b] In parenthesis: relative yield of C-C cleavage
products formed in the ozone ouidation.
This may be exemplified by the oxidation of 2,3-dimethylbutane, which results in 2,3-dimethyl-2-butanol (64%)
and 1,2-epoxy-2,3-dimethylbutane(340/0), and after reduction with lithium aluminium hydride in 97% of the tertiary
alcohol (Scheme 1). Reaction of 2,3-dimethylbutane and
O3 gave only 35% of the tertiary alcohol in addition to acetone (37%) and 3-methyl-2-butanone (28%)16].
12.
LiAlH4
181 A corresponding reaction sequence has been described: E. J. Corey, M.
Shibasaki, J. Knolle, Tetrahedron Lett. 1977, 1625: 0. Hernandez, ibid.
1978. 219.
I
Scheme 1.
Hydroxylation of Acyclic Alkanes
by Oxygen Atoms O(3P)--Comparison of
Ozone and O(3P) Oxidations of Alkanes**
By Elazar Zadok and Yehuda Mazur*
Ozone oxidation of saturated compounds leads to introduction of O H groups at tertiary positions131.This method
is generally applicable to saturated cyclic hydrocarbons,
but not to acyclic hydrocarbons which give comparatively
large amounts of ketones derived from cleavage of C-C
bonds''].
Looking for an alternative method, we utilized ground
state oxygen atoms (O(3P) atoms) generated by low-pressure microwave discharge of a C 0 2 / H e mixture in a flow
system121.We have recently found that 0 atoms produced
in this way convert saturated cyclohexane derivatives
mainly into tertiary alcohols and epoxides['I.
We have now applied this oxidation method to five
acyclic hydrocarbons and have found that also in these
cases the major products were tertiary alcohols and tertiary
epoxides (Table 2). Since reduction of these epoxides with
LiAIH, leads to the same tertiary alcohols, the reduction of
the total mixture of products gave the alcohols in comparatively high yields. The amounts of ketones derived from
C-C
bond cleavage is considerably lower than in the
ozone oxidation (Table 2).
[*] Prof. Dr. Y. Mazur, E. Zadok
Department of Organic Chemistry, The Weizmann Institute of Science
Rehovot (Israel)
[**I This work was supported by the USA-Israel Binational Science Foundation. Jerusalem.
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 4
Although both ozone and O(3P) hydroxylate saturated
hydrocarbons, they operate by different mechanisms.
Ozonation of hydrocarbons involves electrophilic attack of
O3on C-H bonds, leading to reversible formation of a dipolar intermediate from which alcohols (C-H cleavage)
or ketones (C-C cleavage) are formed. Steric effects play
an important role in the ozone oxidation and are responsible in acyclic hydrocarbons for the fact that not only
C-H- but also C-C-bonds can readily be attacked.
The mechanism for the reaction of O(3P) with hydrocarbons probably involves H atom abstraction to form a radical pair"]. Radical combination in a solvent cage leads to
alcohols, while disproportionation of the radicals gives
olefins which are then epoxidized by 0 atoms. This reaction, which occurs when the 0-atom is colinear with the
C-H
bond, has comparatively small steric demandsl'"l
and does not differentiate between cyclic and acyclic hydrocarbons.
Received: August 6, 1981 [Z 45 I€]
German version: Angew. Chem. 92 (1982) 31 I
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982, 606-615
[ I ] E. Zadok, Y. Mazur, J. Org. Chem.. in press.
[2] E. Zadok, D. Amar, Y. Mazur, J. Am. Chem. Soc. 102 (1980) 6369.
[31 Z. Cohen. E. Keinan, Y. Mazur, T. H. Varkony, J. Org. Chem. 40 (1975)
2141.
161 D. Tal, E. Keinan, Y. Mazur, J . Am. Chem. SOC.I01 (1979) 502.
[lo] P. Andersen, A. C. Lunz, J. Chem. Phys. 72 (1980) 5842,5851.
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
0570-0833/82/0404-0303 $ 0 2 . 5 0 / 0
303
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