because of their potential ambifunctional reactivity towards electrophiles and nucleophiles. H. H la. Elektrophile lb. The first alkylidenemalonaldehydes. (1: R1. â.
oo40-4039/89 $3.00 + .OO 3521-3524,1989 Maxwell Pergamon Macmillan plc
Tetrahedron Letters,Vol.30,No.27,pp Printed in Great Britain
SYNTHESIS
AND
STRUCTURE
OF
NOVEL
ALKYLIDENEMALONALDEHYDES:
2-(DIFORMYLMETHYLENE)-1,3_DITHIANE AS
WELL
CHRISTIAN MICHAEL Fachbereich
AS
AND
-1,3-DITHIOLANE
(2,3-DIPHENYLCYCLOPROPEN-1-YLIDENE)MALONALDEHYDE
REICHARDT,:: SCHULZ,
2
Chemie
BERND-VOLKER WERNER der
Hans-Meerwein-StraOe,
2
HERGET, and
MASSA,
’
STEFAN
PESCHEL
Philipps-Universitzt D-3550
Marburg,
Fed.
Rep.
Germany
Summary : The alkylidenemalonaldehydes 4,4-diformyl-1,2-diphenyltriafulvene (41, 2-(diformylmethylene)-1,3-dithiane and -1,3-dithiolane-(8) have been synthesized by various methods, isolated as crystalline substances and studied X-ray analysis.
(11, by
Monosubstituted malonaldehydes are valuable C s-synthons which are completely enol lzed; their reactivity corresponds to that of vinylogous carboxylic acids. Non-enolized alkylidene-malonaldehydes and 2,2_disubstituted malonaldehydes, however, are genuine aliphatic dialdehydes with an enhanced chemical reactiviAs cross-conjugated n-systems, alkyl idenemalonaldehydes J_ are particularly ty. interesting because of their potential ambifunctional reactivity towards electrophiles and nucleophiles.
H
3
H Elektrophile
lb
la
The first alkylidenemalonaldehydes (1: R1 q H; R2 q COzR) have been prepared in situ by Woodward et al. 4 and Used as intermediates in his cephalosporine C synthesis. 5 Alkylidenemalonaldehyde-bisCdimethylacethylacetals) have been synthesized by Reichardt et al., 6 followed by the first syntheses of isolable alkylidenemalonaldehydes by Reichardt et al. 7~8 (benzylidene7 and cycloheptatrienylidene-malonaldehyde 8 and by Arnold et al. 9,lO (aryland diarylalkylidenemalonaldehydes); see reference 1 for a survey of older 1 iterature, and references ll,l* for recent reviews on the chemistry of alkylidenemalonaldehydes.
In syntheses enough cation results.
continuation of our work on aliphatic dialdehydes, of further substituted alkylidenemalonaldehydes to be isolated as crystals and studied by X-ray of Gompper et al. ‘3 gives rise to this preliminary
The idea that structure lb into lidenemalo6ldehyde,
delocalization an aromatic led
to
of ring the
the 14
positive should
synthesis
of 3521
charge stabilize stable
1 we now report which are stable analysis. A recent communication in
the
dipolar
the corresponding C2,4,6-cycloheptatrien-
on
the
publiof our
mesomeric alky-
3522
I-ylidene)malonaldehyde, membered aromatic lonaldehyde. 3 with the subsequent method g brownish-yellow
ring
8 An should
analogous also give
charge delocalization a resonancestabilized
Indeed, acid-catalyzed condensation trimethinium salt 2 in Ac,O/HClOb (70 hydrolysis with lN_HCl at tj5 “C gives (2,3-diphenylcyclopropen-I-ylidene)malonaldehyde crystals with m.p. 183 184 OC
into a threealkylidenema-
of 2,3-diphenylcyclopropenone %> at room temperature - according to Arnold’s 4 with 52% (from cyclohexane).
and yield
as
(I It HCLO, in AczO, - H,O ~21~2H~O~,-2~MeNH,1”C10~ .
,,,C 52 %
0 3
2
4b
4a
The structure of 4 was proven spectrum, and X-ray analysis I> is with I37 pm slightly (Fig. double bond (ca. 134 pm), indicating
mass
Fig.
1.
Crystal 1825
structure reflections).
of
4 ‘5-
by elemental analysis, IR, ‘H, (cf. Fig. 1). The C-l/C-4 bond longer as expected for a normal a small contribution of the
(space
group
PC;
2
=
2;
wR
=
0.056
and
13C
NMR,
length of C(sp2)=C(sp2> dipolar
for
4
3523
form tive
4b. G
The the
plane
of
the
cyclopropene
malonaldehyde
(Z-Diformylmethylene)-1,3-dithiane lithiated Z-trimethylsilyl-1,3-dithiane methylacetal) (5) 16 in extraction with-dichloromethane
(1) tetrahydrofuran-at as follows:
n
OCH,
s f
* H&O
OCH,
Li
slightly
twisted
by
3.5”
x
Illin
s
been obtained by addition to mesoxalaldehyde-1,3-bis(di-70 “C, subsequent hydrolysis
rela-
After
removal of the washed with diethyl m.p. 90 92 OC,
and
12)+ H30@, Room temp. 65 - 75 %
Si(CH,J,
solvent, ether,
of
n
THF, - 78’C
H
6
5
times with
has (6)
0 H&O
is
ring
moiety.
H 7
the to
partially give -7
as
crystalline fine, yellowish
Corresponding 6,6-diformyl-1,3-dithiafulvenes have reaction et al., ‘3 however, starting with “umpol ed” sodium salt of malonaldehyde and 2-methylthio-1,3-dithiolium
product was crystals
been obtained partners such salts.
several (73%)
by Gompper as the
There is even a simpler way to get these alkylidenemalonaldehydes, analogous to Pak et al .: ‘7 direct nucleophillc attack of carbon disulfide by the malonaldehyde anion, followed by a two-fold alkylation reaction of the intermediate anion with l,n-dib;gmoalkanes leads to = 3) and -8 (n = 21, -7 (n however, in rather low yields.
0 K@
DMF.+K,CO,
illin +
S=C=S
12l+Br-ICH4,-~~ II-
IL%
n=2:
8
n=3:
7
The C-2/C-7 bond length of 7 (Fig. 2) is with 139 pm again larger as expected for a normal ~Z(sp~>=C(s~~) double bond (ca. 134 pm), indicating a significant contribution of the dipolar form lb. The SCHAKAL drawing of 7 2) indicates steric interactions betweenthe sulfur and oxygen atoms, (Fig. thus leading to a slightly twisted conformation of 7. The angle between the best planes IC-2/C-7/C-8/O-S/C-9/0-93 and (S-l/C-2/T-3/C-71 is 3.8(Z)“. and C-6 may falsify the geometry of this Disorder of the ring atoms C-4, C-5, region. Acknowledgement: For first successful attempts to synthesize the alkylidenemalonaldehyde 7 in Marburg 1975/76 we thank Dr. E.-U. Wtirthwein, now Professor at tEe Institute of Organic Chemistry, University of Miinster. For the help with the crystal structure determinations we thank Mrs. S. Wocadlo, Marburg. - This work has been supported by the Fonds der Chemischen Industrie, Frankfurt (Main).
