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Conversion of 1 2-Diols into Aldehydes Induced by Photolysis of Alkylcobaloximes A Model System for Dioldehydrase.

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W
R
::;;:;
I :o
x so,
(lc),
=
to success in the cases of I-benzothiepin l,l-dioxides ( I ,)['I,
thiepin l , l d i ~ x i d e [ ~ ~ ,I-benzothiepins
and
( I a)12b.41. We have
now accomplished the synthesis of 1-benzothiepin 1-oxides
( 1 b).
oxides ( 5 ) (in nonpolar solvents) is estimated to lie about
40 to 50°C lower than that of the corresponding l-benzothiepins (4).The half-livesare: ( 5 a ) : 1SS+6 rnin (10"C, CDClJ;
( 5 b ) : S 2 + 2 min (54"C,
CDC13); (4a): 180+7 rnin (59"C,
CDCI,)['l; (4b): 66&2 min (89"C, CC14)r71.
Received: August 25, 1975 [Z 318 IE]
German version: Angew. Chem. 87, 843 (1975)
CAS Registry numbers:
(21. 57458-93-2: (3!> 57458-88-5; i l l ! ) . 37014-56-5; i l h ) , 57458-94-3.
/ 5 0 ) . 57458-89-6: i 5 h ) . 57458-90-9. ( 6 ~ 1 .57458-91-0: l 6 h l . 57458-92-1
[I] Seven-Membered Heterocyclic Compounds, Part 17.-This
[2]
Qy$
H,CO
I
/
J
[3]
[4]
1 4 ~ ) 1461
.
[5]
H,CO
161
0YH5
OR
Since it was to be assumed from numerous unsuccessful
attempts at preparation that unsubstituted ( I 6 ) is less stable
than benzothiepin ( I a ) , R = H, we first prepared the substituted I-benzothiepin I-oxides ( 5 a ) and ( 5 b ) both via the
benzothiepinone I-oxide (3) and by direct oxidation of the
benzothiepins (4a) and ( 4 b)r4a,4b1(Table 1). Apart from analytical data"', smooth further oxidation to the l henzothiepin
1,l-dioxides / 6 a ) and iCib)[sland 'H-NMR data afford structural proof of ( 5 a ) and ( 5 b ) .
[7]
work was
supported by the Fonds der Chemischen Industrie. Part 16: ref. [4b].
i s R. F . Lout,, J. Org. Chem. 26, 2728 (1961); 29,
a ) c' J . T r u ~ i ~ r land
366 119641:
,
, bl, H. Hotmunn and H . !4'rs/eriiuchrr, Anrew. Chem. 78.
980 (1966); Angew. Chem. Internat. Edit. 5, 958 (1966): Chem. Ber.
102, 205 (1969).
W L. M o c k , J. Am. Chem. Soc. KY, 1281 (1967).
a ) H. Hofniunii, B. Mewr, and P. Hofniann. Angew. Chem. 84, 477
(1972); Angew. Chem. internat. Edit. / I , 423 (1972); b) H. H~fmuiin.
I f . - J Huhrrstroh, B . A p p l r r , 8. M e w r , and lf. Hrrrrrich. Chem. Ber.
/OR. 3596 (1975); c) D. N . Rrrii/io~rdrand C . G. K o i i i v e i i l ~ o v ~ ~J i.i ,Chem
Soc. Chem. Commun. 1972. 1232; d ) c' .I.
7?uriidi.s, E ~JshihaLvu,J.
C. Sih. and L. J. Miller, J. Org. Chem. 38. 3978 (1973); e) J . M u r u i u ,
7 Tutsuoku. and J . Sugihuru, Angew. Chem. 86, 161 (1974); Angeu.
Chem. internat. Edit. 13, 142 (1974).
Correct elemental analyses were obtained for all new compounds The
( = [ M - S O ] + ) as
mass spectra of ( 5 u ) and ( 5 6 ) contain [M-48]'
the base peak, while the mass spectra of the considerably more stable
sulfones ( 6 u ) and (66) contain the nonfragmented molecular ions.
W S/eg/ichand G. Hour, Angew. Chem. 81, 1001 (1969); Angew. Chem.
internat. Edit. 8, 981 (1969).
R. Heidrich, Diplomarbeit. Universitat krlangen-Nbrnberg 1975.
Conversion of 1,2-Diols into Aldehydes Induced by Photolysis of Alkylcobaloximes:
A Model System for Dioldehydrase[**]
By Bernard 7: Golding, Terence J . Kernp, Enrico Nocchi, and
William P . Watson[*]
5'-Deoxy-5'-adenosylcobalamin(AdoCbl) acts as a coenzyme for the conversion of certain 1,Z-diols into aldehydes
catalyzed by the dioldehydrase of Aerobacter aerogenes"!
In these reactions enzymatically-induced homolysis of the
cobalt-carbon bond of AdoCbl is followed by attack of the
Table I.Preparation of 1 3 ) . ( 5 a ) , ( j h ) , ( 6 ~ )and
.
(6h).
Cpd.
Preparation
'H-NMR [a]
Yield
[''lo]
M.p.
i ('1
(31
(5u)
(56)
(6u)
(66)
from ( 2 ) ; with m-chloroperbenzoic acid (molar ratio 1 :I)in CH,C12, 12 h at -20°C [b]
from(3):with AcZO/Et,N/p-dimethylaminopyridine[6],24hat -30"C:precipitated from CH,C12
at -20°C with light petroleum
from ( 4 u ) : with in-chloroperbenroic acid (molar ratio I : 1 ) in CH2CI,, 5 b at -20°C [b]
from (3): with K O t B u h e t h y l fluorosulfate in THF, 5 h at - 120°C [c]
from ( 4 h ) : with in-chloroperbenroic acid (molar ratio I : I) in CH,Cl,, 1 2 h at -20°C [c]
from ( 5 ~ ) as
: for ( 5 h ) from ( 4 b )
from ( 4 ~ ) with
:
in-chloroperbenzoic acid (molar ratio 1.2) in CH,CI,, 1 2 h at -25°C
from ( 5 h ) . as for ( 5 6 ) from ( 4 h i
from 1 4 h ) . as for ( 6 u ) from ( 4 a )
3.85
95
71
I32
72
(dec )
4.61
3.37
3.96
89
86
80
85
85
70
81
105
I52
142
[a] 2-H (s); CDC13, T values in ppm.
[b] Precipitated with light petroleum
[c] Crystallized from methanol.
Expectedly, ( 5 a ) and ( 5 b ) are thermally less stable than
the parent I-benzothiepins (4a) and ( 4 b ) . O n warming in
an inert solvent they readily eliminate SO to form the naphthalenes ( 7 a ) and ( 7 b ) respectively[4h1without formation of
any further reaction product being detectable in the 'H-NMR
spectrum. From a comparison of the half-lives for thermal
decomposition of ( 5 a ) and ( 5 b ) with those of ( 4 a ) and
(4 b), respectively, the stability range of I-benzothiepin 1-
[*I
I'[
Dr. B. T. Golding [ '1. Dr. T. .I. Kemp, Dr. E. Nocchi. and Dr. W.
P. Watson
Department of Molecular Sciences. University of Waruick
Coventry CV4 7AL (England)
T o whom correspondence should be addressed.
[**I
Financial support was given by the Science Research Council (to M! P. M:)
and by the Academia Narionale dei Lincei (to E . N . under the auypices
of the Royal Society European Exchange Scheme). -We acknowledge excellent technical assistance from L. C Curr and C . ,Yonn.
813
resulting 5'-deoxy-5'-adenosyl radical on the substrate (SH)
giving 5'-deoxyadenosine and the radical S*.The latter is somehow transformed to radical P' which abstracts a hydrogen
atom from 5'-deoxyadenosine, thereby regenerating the 5'deoxy-5'-adenosyl radical and producing a 1,I-diol (PH), from
which product aldehyd? arises[21.
similar reactions which ensue followWe have pointed
ing attack of hydroxyl radicals on 1,2-di0ls[~l,e . g . :
HOCH,CH,OH
- OH
H O C H ~ ~ H OH+
(a)
H z 0 + *CH,CHO
An even more compelling model system would achieve
the nonenzymatic formation of an aldehyde from a 1,2diol
with the help of an alkyl radical R' derived from an alkylcobalt
compound like AdoCbl:
R ~ C H O H C H ~ O-%
H
-
R~CHOHEHOH
H-atom
H,o + R ~ ~ H C H O
(b)
R'CH,CHO
acetic acid in the presence of oxygen, only a trace of pentanal
was obtained (50.5 % yield). The main product derived from
the 4,s-dihydroxypentyl group of (2) in anaerobic photolyses
was 1,2-pentanediol ( N 50 % yield).
We propose that pentanal arises as follows in the anaerobic
photolysis of (2): Photoinduced homolysis of the Cobond of (2) gives the 4,s-dihydroxypentyl radical which mainly
becomes 1,2-pentanediol, but partly undergoes a specific hydrogen transfer (favored by a six-membered cytlic transition
state"]) to generate the radical n-C3H7CHOHCHOH; acidcatalyzed re~rrangementL3~
4a1 of this radical can give the radical n-C3H ,CHCHO which produces pentanal after a hydrogen
atom abstraction (from a source to be determined).
Although enzymatic reactions involving dioldehydrase and
AdoCbl are not photochemically inducedt8],we submit that
the clean, rapid photohomolysis of alkylcobalt compounds
justifies the use of photolyses in model experiments. We predict
that the 4,5-dihydroxypentyl radical plays a similar role to
the 5'-deoxy-5'-adenosyl radical in the enzymatic system, by
performing a selective hydrogen atom abstraction on a 1,2di0l[~1.
\""me
We now report our experiments in the pH range 2-3,
which apparently demonstrate transformations of the type
in eq. (b).
A de-aerated solution of methyl(aquo)cobaloxime (
(4mM)in aqueous KCI/HCl buffer (pH 2.0) containing 1,2-ethanediol (1.0 M) was photolyzed [h= 380+ IS nm, chargetransfer band of (Z)]. The disappearrince of ( I ) followed
the classical form [IT(- 1)=0.14+0.01] giving Co;:,
free
ligands, and acetaldehyde [isolated as its 2,4-dinitrophenylhydrazone: yield N 10 % (estimated by NMR spectroscopy);
5 % isolated]. No acetaldehyde was produced in reaction
mixtures kept in darkness for the duration of photolyses
(45 min)16].The yield of acetaldehyde given is based on cobaloxime and is 250 x lower when related to 1,2-ethanediol. This
is evidently due to the low probability of intermolecular attack
of methyl radicals on 1,2-ethanediol and/or to the lack of
?n efficient chain process emanating from the radical HOCH,CHOH. As the concentration of 1,2-ethanediol increases,
so does that of acetaldehyde, presumably due to the increasing
efficiency of the captur: of methyl radicals with production
of the radical HOCHzCHOH and hence of acetaldehyde (cf.
eq. (a) and refs. [4a, 4cl).
Received: August 13. 1975:
in abbreviated form: September 2, 1975 [Z 312 IE]
German Qersion:Angew Chem. 87. 841 (1975)
CAS Registry numbers:
Methyl(aquo)cobaloxime, 25360-55-8; 1.2-ethanediol, 107-21-1 ;
acetaldehyde, 75-07-0: 4.5-dihydroxypentyl(pyridine)cobaloxime,
57031-36-4; pentanal, 110-62-3
Cf. H. A. Burkw, Annu. Rev. Biochem. 41, 55 (1972).
[2] T H. Finlay, J . Vulinskr, K . Saro, and R. If. Abdes, J. Biol. Chem.
247, 4197 (1972).
[3] B. T Goldrrzy and L. Rodo~ii,J. Chem. Soc. Chem. Commun. IY73.
939.
[4] a ) B . C. Gilbwt, J . P . Lorkin, and R . 0. C. Norriian, J. Chem. Soc.
Perkin II 1972. 794: b) K . M . Bunsol. M . G r U r A A. Hrrrgkin, and
E . Joriufn, J. Phys. Chem. 77. 16 (1973):c) C Wdlizq and R A. Johri\o~i.
J. Am. Chem. Soc. 97, 2405 (1975).
[5] Alkyl (base)cobaloximesare bis(biacetyldioximato)cobalt complexes with
a o-alkyl group and a Lewis base as axial ligands, used as models
for alkylcobalamins [cf. C . N . Sc/ir.arrzer, Acc. Chem. Res. 1, 97 (196X)l.
Syntheses of ( 1 ) and ( 2 ) : B T Golrliiig ef a/., to be published
[6] In the control experiments mentioned, 20.2"4 yield (based on cobaloxime) of acetaldehyde or pentanal would have been detected.
[7] J . W Wilt in J . K . Kodii: Free Radicals. Wiley-lnterscience, New York
1973. Vol. 1. Chap. 8, p. 380
[S] See, however. T Yumane. S. Shiiiii;ii, and S. Firkui, Biochim. Biophys.
Acta 110, 616 (1965).
[9] IA-Hydrogtn transfer in the 4.5-dihydroxypentyl radical giving the radical n-C3H , C O H C H 2 0 H , followed by acid-catalyzed rearrangement""'.
would yield 2-pentanone which was not detected after photolysis of
(21.
[l]
Thermal Cycloaddition between 3,6-Dijhenyl-s-tetrazine and 9-0xabicyclo[6.1.0]nona-2,4,6-triene; Construction of the Oxonino[4,5-d]pyridazine Frame[**'
By A . G. Anastassiou and S . J . Girgend']
4,5-Dihydroxypentyl(pyridine)cobaloxime (2)[51 contains
both a 1,Zdiol and potential alkyl radical; hydrogen atom
transfer between radical and diol can then bc nn intramolecular
process. Photolysis (h= 380+ 15nm) of a de-aerated solution
of (2) [ 3 . 5 m ~ ]in 0.1 M aqueous acetic acid (pH 3.0) gave
pentanal [isolated as dinitrophenylhydrazone in 3.5 k0.3 %
yield (three experiments)]. Control experiments performed in
the dark [storing the following compounds in 0.1 M acetic
acid : (2) (3.5 mM); 1,2-pentanediol (3.5mM); 1,2-pentanediol
( 2 . 8 m ~ and
)
cobalt(ii) acetate ( 4 m ~ ) ]gave no detectable
pentanalLh1.
Photolysis (h=380* 15 nm) of a de-aerated solution containing biacetylglyoxime (7 mM), cobalt(1r) acetate
(3.5mM), and 1,2-pentanediol (3.5mM) in 0.1 M acetic acid
also gave no pentanal''! When (2) was photolyzed in 0.1 M
814
In an attempt to extend the scope of the pericyclic synthesis
of novel n: systems[" to molecules containing more than one
heteroatom we examined the synthetic potential ofdiphenyltetrazine (2)[" as a pericyclic trap of properly structured molecules. In this report we briefly describe the use of (2) in
the first successful thermally activated cycloadditive trapping
of 9-oxabicyclo[h.l .O]nona-2.4,6-triene (1) to produce an oxa[*] Prof. Dr. A. G. Anastassiou and S. J. Girgenti
Department of Chemistry, Syracuse University,
Syracuse, New York 13210 (USA)
[**I We thank the National Science Foundation (GP-38553X)and the Petroleum Research Fund, administered by the American Chemical Society. for
support of this work.-We
should also like to express our appreciation
to Mr. L. MrCmdless for the determination of the IOOMHz spectra.
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aldehyde, photolysis, alkylcobaloximes, mode, induced, diols, dioldehydrase, system, conversion
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