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Nucleophilic Acylation with -Acyl Enamines.

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pounds exhibiting sp3 configuration at the aldehydic C atom.
The CH acidity of sp2 configurated C atoms is known to be
greater than that of sp3 configurated C atoms. However, this
phenomenon can hardly be exploited in the case of the aldehyde itself, since addition to the carbonyl group proceeds
considerably faster than dissociation of the aldehyde proton.
Having observed that 1,4-dihydronicotinamide derivatives
( I ) can be deprotonated at C-2r41 we attempted to perform
nucleophilic acylations with functionally substituted aldehydes. For this purpose we converted the P-acyl aldehydes
(2) into the enamines (3); the nonparticipating carbonyl
group was not protected. The first experiments with various
bases showed, however, that in compounds of type (3) Michael
addition and addition to the carbonyl group are faster than
deprotonation. Nevertheless, it was also observed that the
temperature dependence of these competing reactions differs.
Below -100°C deprotonation is faster so that (3) affords
the P-acylvinyl anion (4)[51almost quantitatively. Presumably,
complex formation with the neighboring carbonyl group plays
a role hereC4].Once formed, the anion ( 4 ) is stable at least
up to room temperature. It can be deuterated with CH30D,
alkylated with alkyl iodides, and acylated with esters to give
polyfunctional components (Table l)@J.
Our observations demonstrate that the Co-C bond of
enzyme-bound ( I ) is not alternately closed and broken during the catalytic reaction with the substrate. If this were
so, irradiation of the enzyme complex should not have had
any significant effect on the rate of the subsequent enzymatic
reaction in the dark.
The present results do not necessarily support the currently
popular idea that coenzyme B, dependent enzymatic reactions occur cia organic radicals and that the coenzyme is activated enzymatically by the homolysis of the C
4 bond. On
the contrary, our findings are fully consistent with the previously postulatedr7- heterolytic mechanism of enzymatic
coenzyme B,,-activation"
Received: January 22. 1976 [Z 379 IE]
German version: Angew. Chem. 88,186 (1976)
S. S. Krrwur. 7: A. Smith, and R. H . Ahelrs, J. Biol. Chem. 245, 1169
(1 970).
[2] R. H . Abrles, Adv. Chem. Ser. 100, 346 (1971).
131 G. N . Sando, R . L . Blukley, H . P . C . Hogenkump, and P. J . Hofmann,
J . Biol. Chem. 250, 8774 (1975).
[4] Commercial enzyme, obtained from Pierell S.p.A., Milan (Italy).
[ 5 ] An Hg-vapor lamp manufactured by W. Gates Co. (Model 420-U I),
360 W, was employed for the experiments.
[6] R. G . S. Bunks, R. J . Henderson, and J . M . Pratt, J. Chem. SOC. A 196H,
[7] G. N . Schruuzrr and J . W Sibrrt, J. Am. Chem. SOC.92, 1022 (1970);
G. N . Schraurrr, J . A. Seck, and R. J . Holland, 2. Naturforsch. 28c,
1 (1973).
[XI Vitamin B I Z \ was detected unambiguously by measurements of the
optical absorption spectra and subsequent alkylation with CHJI.
[9] R. Yumodu, S. Shimzu, and S. Fukui, Biochim. Biopbys. Acta 124, 197
(1966).-On photolysis of higher alkylcobalamins which contain hydrogen in the P-position, alkyl radicals are formed initially. These transfer
one electron to the cobalt ion of the corrin with attendant formation
of olefins; see: G. N . Schruuzer, J . W Sihert, and R. J . Windgussen,
J. Am. Chem. Soc. 90, 6681 (1968); G. N . Schraurer, L. P . Lee, and
J . W Siherf, ibid. 92, 2997 (1970).
[lo] G . N . Srhmuzrr and E . A . Srodlhauer, Bioinorg. Chem. 4 , 185 (1975).
[ I l l For light-induced activation of a complex of the dioldehydrase with
other coenzyme B,, analogs, see T Yumane, S. Shimim, and S . Fukui,
Biochim. Biophys. Acta 110,616 (1965).
(I), R = A l k y l
Table 1. Compounds prepared [a]
'H-NMR [b]
4.85 (s)
4.73 (s)
4.53 (s)
4.97 (s)
4.95 (s)
7.81 (d)
2.52 (s)
2.93 (q)
8.18-7.20 (m)
7.87-7.22 (m)
150 [d]/IO-'
155 [d]l10-2
2.37 ( s )
["XI [c]
_____ ____ _______ _ _ _ _ _ _ _ _ __ _ _ __ _ _ _ _ _ _
_ _
All compounds gave correct elemental analyses.
6 values; CDCI,, TMS internal standard.
Conversion based on reactant. About 7 M 0 % of the amount formed in each case was isolated.
Furnace temperature on bulb tube distillation.
Nucleophilic Acylation with P-Acyl Enarnines[***'
By Richard R . Schmidt and Jorq Talbierskv[']
Nucleophilic acylation with CH acidic aldehyde derivatives
has acquired considerable preparative significance['3zJ.Important aldehydic intermediates appearing in this connection are
1,3-dithianes['I and P-trimethylsilyloxy cyanidesi3], i.e. com~
[*] Prof. Dr. R. R. Schmidt'"' and J . Talbiersky
lnstitut fur Organische Cheniie, Biochemie und lsotopenforsckung der
Pfaffenwaldring 55, 7000 Stuttgart 80 (Germany)
I**1 Present address: Fachbereich Chemie der Universitat
Postfach 7733, 7750 Konstanz (Germany)
[***] This work was supported by the Fonds der Chemischen Industrie
and by the Deutsche Forschungsgemeinschaft.
Anqew. C h r m . Int. Ed. Engl. i Vol. 15 (1976) N o . 3
N,N-Diethyl-3-pyrrolidinoacrylamides( 5 )
To a solution of (3) (0.78 g, 4 mmol) in anhydrous T H F
(30ml) prepared under N2 is added at -115°C a solution
of tert-butyllithium(4.2 mmol) in n-pentane (ca. ,6 solution),
After 30min the temperature is allowed to rise to - ,05 oc,
After another 2.5h, the electrophileR3,x (8 mmol) is added
to the reaction mixture. The solution is warmed to room
temperature and worked up with chloroform/water after 3 h.
The products ( 5 ) were isolated by distillation (see Table 1).
Received: January, 8, 1976;
supplemented: January 30. 1976 [Z 383 IE]
German version: Angew. Chem. 88. 193 (1976)
CAS Registry numbers:
( 2 ) . 58343-35-4; ( 3 ) . 58343-36-5; / S u ) . 58343-37-6,
( S b ) , 58343-38-7; ( S c ) , 58343-39-8; [SdJ, 58343-40-1 ;
( S e ) , 58343-41-2; H-OCH,.
67-56-1 : D-OCH,,
74-88-4; CH,CH,--I,
75-03-6; C,H,CO-OCH,,
94-08-6: p) I rolidine, 123-75-1
[ I ] p-Acylvinyl Anions, Part 1.
[Z] D. Serbuch, Angew. Chem. 81, 690 (1969); Angew. Chem. Int. Ed. Engl.
8, 639 (1969); Synthesis 1Y69, 17.
[3] K . Deuchert. U . Herfenstein, and S . Hiinig, Synthesis 1973, 777; S. Hiinlg
and G. Wehrier, ibid. 1975, 180, and references cited thereln.
[4] R. R. Schniidr and G. Bergrr, Chem. Ber., in press.
[S] For other attempts to generate 0-acylvinyl anions, see R. R. Schmidt,
Lecture at “Chemiedozententagung”, Stuttgart, April 1974; K . Kondo
and D. Tunernoto, Tetrahedron Lett. 1975, 1007. 1397.
[6] In enamine systems other than (3)/tBuLi, account must also be taken
of the deprotonations of methine groups located CY relative to the enamine
double bond observed by Ahlbrecht [7] and Tlioirlp.w~i[S].
[7] H . Altlhrecht and C . Vonderheid, Synthesis 1975, 512, and references
cited therein.
[S] H . W Thompson and B . S. Huegi, J. Chem. Soc. Chem. Commun. 1973,
We have now succeeded in performing the reverse reactions
of ( 2 a ) and (2b) (X = BF,), respectively, with Co2+and synthesizing the trinuclear complexes ( 1 a ) and ( 1 b ) from the
corresponding cationic monocyclopentadienylcobalt compound. Instead of compounds (2), the salts [C5H5Co{PO(OR)2j3BF]BF4[31obtainable from them can be used as
starting material. Also other transition metal ions M z + react
analogously to Co2 ; hence, trinuclear complexes of the
general composition (C5H5)2C02M[PO(OR)2]6 ((3b),
M = M n ; ( 4 b ) , M=Fe; (5a,b), M=Ni; (6a,b), M=Cu;
(7a,b), M=Zn; (Sb), M=Cd; R=CH3 ( a ) , C2H5 ( b ) ) containing two dflerent metals as coordination centers in the same
molecule are accessible cia this route (see Scheme 1).A suitable
solvent for the reaction is aqueous methanol, in which the
salt-like starting compounds are readily soluble, whereas the
neutral trinuclear complexes are very sparingly soluble. The
syntheses of (3)-(8) are therefore preferably carried out as
precipitation reactions.
Synthesis of Trinuclear Sandwich-Like Cyclopentadienyl Complexes Containing Two Different Metal
Atom Centers[**]
2 (2) + c o x ,
By WoEfgang Klaui and Helmut Werner“]
Reaction of bis(q-cyclopentadieny1)cobalt (cobaltocene)
with dialkyl phosphonates leads to trinuclear complexes of
type ( I ) in almost quantitative yield:
3 C O ( C S H ~+) ~6 HPO(OR),
M = Fe
According to a crystal structure determination carried out
on ( l a ) [ ’ ]the three cobalt atoms are arranged linearly. Two
of them are equivalent, each being coordinated with a cyclopentadienyl ring and the phosphorus atoms of three phosphonato groups; the third (central) cobalt atom is located
at a center of symmetry and is surrounded octahedrally by
six oxygen atoms. ( l a ) and ( l b ) are not attacked by air
and are so stable thermally that they can be sublimed undecomposed at 250°C in a high vacuum.
During investigations on the reactivity of the trinuclear
complexes ( I n ) and ( I b ) we recently found that they react
with concentrated mineral acids HX and undergo protonation
at the oxygen atoms. From conductivity measurements and
NMR data it can be concluded that an equilibrium is established[’] :
Dr. W. Klaui and Prof. Dr. H. Werner[+]
Institut fur Anorganische Chemie der Universitit
Ramistrasse 76, CH-8001 Zurich (Switzerland)
[+]Author t o whom correspondence should be addressed. Present address:
lnstitnt fur Anorganische Chemie der Universitat
Am Hubland, 8700 Wiirzburg (Germany)
[**I This work was supported by the Schweizerischer Nationalfonds zur
Unterstiitzung der wissenschaftlichen Forschung. We thank Herr L . Beck foi
his valuable participation in the experimental work.
1 I7
As the X-ray powder diagrams of ( I b ) and ( 3 b F f 8 b )
illustrate, all these compounds are isotypic and therefore probably have a similar structure to that of (la)“]. The trinuclear
complexes are, with the exception of (4b), light-yellow, easily
crystallizable solids which are stable towards air and moderately to readily soluble in CCI,, CHCl,, and CH2C12. (4b)
is brownish-violet; it is oxidized by air only slowly in the
solid state, but rapidly in solution. Oxidation leads quantitatively to the yellow cation [(C,H5)2C02Fe{PO(OC2H5)2)6]
which formally contains Fe3+ as central atom and can also
be obtained directly by reaction of ( 2 b ) (X = BF4)or [C5H5Co(PO(OC,H,)2},BF]BF, with FeC1, (see Scheme 1).The tetrafluoroborate salt of this cation has solubility properties largely
resembling those of [C5H5Co(PO(OC2H5)2}3BF]BF4,i.e. it
is readily soluble in acetone, methanol, methylene chloride,
but insoluble in CCl, and hydrocarbons.
Like ( I ), the trinuclear complexes (3)-(6) are also paramagnetic. The ’H-NMR spectra of the diamagnetic species
( 7 6 ) and ( 8 6 ) are almost identical and show no influence
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acylation, acyl, nucleophilic, enamine
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