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First 1 4-Dipolar Cycloadditions of 6-Oxo-3 6-dihydro-1-pyrimidinium 4-Olates to Ketenes and Other Carbonyl Compounds.

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tively. The six internal angles are all within 119.7+ 1.2"
and sum up to 718.1", compared to 120" and 720" in benzene. Hence the six electrons of the C(21)-C(22),
C(4 l)-C(42), and C(61)-C(62) cyclopropane backbon:
are well placed for a circumannular, conjugative interaction via the three carbonyl groups.
In this respect it should be mentioned that the distal cyclopropane bonds in 2 (mean value 144.6 pm) belong to
the shortest single bonds so far found in cyclopropane ring
systems.['*]These bonds, if shortened by interaction with
an electron acceptor are usually in the range 145-150 pm,
whereas the mean bond length in cyclopropane derivatives, calculated from 115 examples is 150.9(2) pm.l'zl The
bond lengths in the six-membered ring of trispirotriketone
2 are also very short when compared to the standard C-C
bond length of 154 pm or the comparable mean internal
C-C length of 152.1 pm in 10.
Received: April I , 1985;
supplemented: May 14, 1985 [Z 1247 IE]
German version: Angew. Chem. 97 (1985) 599
CAS Registry numbers:
2, 96999-00-7: 3, 59078-46-5; 4, 96-48-0: 5, 52412-07-4; 6, 29547-04-4; 1,
96999-01-8; 8 , 89544-84-3; 9 , 96999-02-9.
[I] G. J. Baxter, R. F. C. Brown, F. W. Eastwood, K. J. Harrington, Tefrahedron Lett. 1975, 4283; see also J . L. Ripoll, Tetrahedron 33 (1977) 389.
[2] a) C. Sabieraj, unpublished experiments; h) J.-M. Wulff, H. M. R. Hoffmann, Anqew. Chem. 97 (1985) 597; Angew. Chem. Int. Ed. Engl. 24
(1985) 605.
[3] The base-catalyzed rearrangement of certain non-enolizable 1,3-cyclobutanediones into 1,3,5-cyclohexanetrioneshas been ob%erved: J. L. E.
Erickson, F. E. Collins, Jr., B. L. Owen, J. Org. Chem. 31 (1966) 480: J.
L. E. Erickson, G. C. Kitchens, ibid. 27 (1962) 460. However, 3 has four
spiroactivated methylene carbons, and on treatment with nucleophiles
presumably suffers homoconjugate Michael addition.
(41 Cf. H. W. Pinnick, Y. H. Chang, S . C. Foster, M. Govindan, J. Org.
Chem. 45 (1980) 4505: P. M. Warner, D. Le, ibid. 47 (1982) 893; E. G. E.
Jahngen, D. Phillips, R. J. Kobelski, D. M. Demko, ihid. 48 (1983) 2472;
I. Reichelt, H.-U. Reissig, Chem. Ber. 116 (1983) 3895; Liebigs Ann.
Chem. 1985, 650; L. A. Paquette, C. Blankenship, G. J. Wells, J . Am.
Chem. SOC.106 (1984) 6442.
[5] a) Preparation of 8 by another route: J. P. Barnier, G. Rousseau, .I.M.
Conia, Synthesis 1983, 915; P. Bruylants, Bull. SOC.Chim. Belg. 32 (1923)
358. b) Cf. also L. Fitjer, Chem. Ber. 115 (1982) 1035; we thank Professor
Fitjer for a sample of 9 .
161 Other recent applications of this technique: H. M. R. Hoffmann, K.
Haase, Synthesis 1981, 715; H. M. R. Hoffmann, L. Iranshahi, J . Org.
Chem. 49 (1984) 1174 and intervening papers.
[7] Experimental procedure: A solution of 9 (17.5 g, 95 mmol) in absolute
acetonitrile (25 rnL) was added dropwise to a suspension of zinc (18.7 g,
0.29 mol) and copper(1) chloride (0.28 g, 2.9 mmol) in acetonitrile
(25 mL), previously warmed to 40°C. During addition of 9 the reaction
mixture was allowed to reflux. The mixture was refluxed for a further
30 min, allowed to reach room temperature and the products were extracted with pentane. Column filtration (silica gel, pentane) furnished
white crystals (3.9 g, 61%) of 2 3 (molar ratio 2 : 3 = 2 : 3 by 'H-NMR).
The bulk of 3 was removed by sublimation, leaving 2 which was purified by chromatography on silica gel. Spectroscopic data of 2: IR (KBr):
3120 (w). 3020 (w) (cyclopropane C-H), 1668 ( s ) (C=O), 1358 ( s ) , 1 1 10
( s ) c m - ' . 'H-NMR (CDCI,): S= 1.98 ( s ) . "C-NMR (CDC13): S=29.26
(6CH2), 40.68 (3 spiro C ) , 202.22 (3C=O): 'JcH=169 Hr.
[8] X-ray .wucfure analysis: P2,/c, a=8.550(2), b = 15.665(6), c=8.408(2)
p= 118.49(3)", p'.,,<=1.370 g cm-', 1355 observed of 1746 independent
reflections 112 1.250(f)], R =0.048, Syntex-P2,-diffractorneter,MoK, radiation (d=0.71069
28,.,,=50". Further details of the crystal structure investigation are available on request from the Director of the Cambridge Crystallographic Data Centre, University Chemical Laboratory,
Lensfield Road, Cambridge CB2 IEW (England).
[9] H. M. R. Hoffrnann, M. B. Hursthouse, L. New, Tefrahedron 37 (1981)
1967.
[lo] H. M. R. Hoffrnann, M. B. Hursthouse, J . Am. Chem. SOC.98 (1976)
7449.
[ I I] H. R. Buys, H. J. Geise, Tetrahedron Lett. 1970, 2991; R. Bucourt, Top.
Srereochem. 8 (1974) 159.
[I21 Review: F. H. Allen, .4cta Crystallogr. 836 (1980) 81.
First 1,4-Dipolar Cycloadditions of
6-0xo-3,6-dihydro-l-pyrimidinium4-Olates to
Ketenes and Other Carbonyl Compounds**
By Hans Gotthardt* and Karl-Heinz Schenk
Dedicated to Professor Rolf Huisgen on the occasion of
his 65th birthday
6-0xo-3,6-dihydro- I-pyrimidinium 4-olates of type 3
are capable of undergoing [4 21-cycloadditions to certain
CC-multiple bond systems,l'I and even to singlet oxygen;"]
such additions have opened up interesting entries to pyridone derivatives and heterobicycles. In contrast, analogous [4+2]-cycloadditions of 3 to CO double bonds have
so far never been described. We report here on an improved synthesis of 3 and on the first 1,4-dipolar cycloadditions of 3 to ketenes, formaldehyde, hexafluoroacetone,
and mesoxalates. These reactions lead to the formation of
novel stable primary adducts in high yields.
The synthesis of compounds 3a, bI3] unsubstituted in
position 5 has hitherto only been accomplished by reaction
of the amidines 2 with carbon suboxide. The preparation
of carbon suboxide from malonic acid, however, is somewhat expensive and yields of only 10-20% are ~ b t a i n e d . ' ~ ]
More advantageous is the synthesis of 3a, b via modification of the known methodi5] of heating a dry equimolar
mixture of 2 and bis(2,4,6-trichlorophenyl) malonate 1 to
140--170"C/ <0.01 torr, whereby the liberated 2,4,6-trichlorophenol is immediately distilled off from the melt. Recrystallization of the melt from ethanol affords 3a or 3b.
The new compounds 3c-e (Table 1) and 7I6l are obtained
analogously from 2 or 6, respectively, and bis(2,4,6-trichlorophenyl) methylmalonate 1 .
+
R~CH(CO~C,H,CI,),
PhNH
+
NPh
\c4
I
R1
1
2
- 2 CBH,C1,OH
.
+
A,
A),
608
0 VCH V e r l a g . ~ g e . ~ e i ~ ~mhH,
c l i a ~0-6940 Weinheim. 1985
Table 1. 6-0x0- 1,3-diphenyl-3,6-dihydro-l-pyrimidinium4-olates 3 from
bis(2,4,6-trichlorophenyl) malonates 1 and N,N'-diphenylamidines 2.
3
R'
R2
Yield
M.p. ["C] [a]
[4/01
[b]
b [b]
a
C
d
e
Me
Ph
H
Me
Ph
H
H
Me
Me
Me
79 (71)
65 (76)
71
98
78
248-249(260-261)
255-257 (255-257)
229-230
286-287
291-292
IR (KBr)
v(C=O) [cm-'1
1670
1655
1678, 1640
[a] Decomposition. [b] Data quoted in the literature [3] given in brackets.
['I
Prof. Dr. H. Gotthardt, DipI.-Chem. K.-H. Schenk
Lehrstuhl fur Organische Chemie der Universitat
Gauss-Strasse 20, D-5600 Wuppertal I (FRG)
[**I This work was supported by the Fonds der Cbemischen Industrie and
by Bayer AG.
0570-0833/8S/0707-0~08S 02.50/0
Angerw. Chem. i n f . Ed. Engl. 24 (19SSj No. 7
When 3a is allowed to react with diphenylketene (molar
ratio 1 : 1.27) in acetonitrile at 20"C, colorless needles of
4a crystallize out whose structure and composition are
consistent with the elemental analysis and spectroscopic
data."] The mode of addition of the ketene in 4a follows
quite clearly from the I3C-NMR spectrum, which shows
the resonances of C - l and C-4 at 6 = 101.11 and 58.24, respectively. The opposite mode of addition would lead to
bonding of the oxygen with the unsubstituted C-atom, and
the "C-resonance would then be shifted downfield to
6=84.80.1'1 In an analogous way, 3b and diphenyl ketene
or dimethyl ketene afford, after crystallization from ethyl
acetatelhexane, 4b and 4c,['I respectively (Table 2).
CRZ
R3 R3
I/
/
I
\/
+
of a thermally allowed [,4, .2,]-cycloaddition to give the
sterically more demanding adducts 4a-c.
6
7
8
Even formaldehyde-generated in situ from paraformaldehyde by depolymerization at 110°C-reacts with 3b-d
or 7 regiospecifically to give the adducts 5a-c and 8,1'21
while hexafluoroacetone already combines with 3d at 0°C
to give 5d . [ I 3 ] Furthermore, diethyl mesoxalate cycloadds
to 3c, e at 110°C with formation of 5e, f.[I4]The uniform
regiochemistry in the adducts 5 follows from the I3CN M R spectra.
Received: December 6, 1984 [ Z I100 IE]
German version: Angew. Chem. 97 (1985) 604
Publication delayed at authors' request
I
*Ph/ R'm
\
Ph/
Ph
R'
\
Ph
CAS Registry numbers:
Table 2. 6,7-Diphenyl-2-oxa-6,7-diazabicyclo[2.2.2]octane-5,8-diones
4 and 5
as primary adducts from 3 and carbonyl compounds.
4a
4b
4c
5a
5b
5c
5d
5e
5f
R1
R2
R'
Yield [%I
M.p. [ T I
Me
Ph
Ph
Ph
H
Me
H
H
H
H
Me
Me
Me
Me
H
Ph
Me
Ph
Ph
Me
H
H
H
C F,
C02Et
C02Et
74
88
93
83
99
68
87
88
74
173.5-174.5 [a]
191-193 [a]
174- 177 [a]
175-177
176.5- I77
224-225 [a]
286-287 [a. b]
130-131
149.5-150 [a]
Me
[a] Decomposition. [b] On heating, decomposes into hexafluoroacetone and
3b, recognired by its melting point.
The solvent has very little influence on the rate constant
k2 of the cycloaddition of 3a to diphenyl ketene; k , shows
an inverse dependence on the solvent polarity, as indicated
by the ratio k,(dioxane)/k2(acetonitrile) = 2.5. This suggests a diminution in charge in the transition state and is
consistent with a concerted mechanism. Analogous inverse
solvent dependencies of the same order of magnitude have
also been observed in the [3 21-cycloadditions of the sydnones to alkynes,['I whereas the k2 values in the multistep
[2 21-cycloadditions of tetracyanoethene, which proceed
via dipolar intermediates, increase with increasing solvent
polarity by factors of u p to 63 OO0.[91
The 1,4-dipolar cycloadditions of 3a, b to the CO-double bond of ketenes are remarkable, since reaction of ketenes with 1,3-dienes usually yields cyclobutanone derivatives according to a [,2,+,2,] process, with the C C double
bond of the ketene functioning as antarafacial component.'"' ] I 1 Since the concerted 14 + 21-cycloadditions of 1,3dienes to the ketene CC double bond are thermally forbidden as a [,4, .2,] process according to the rules of conservation of orbital symmetry,["I ketenes apparently d o not
react with the C C double bond, but specifically and regioselectively with the C O double bond of 3a, b in the sense
+
+
+
Angew. ChiJm.I n f . Ed. Engl. 24 11985) No. 7
l a , 15781-70-1; lc, 15781-71-2; Za, 621-09-0; Zb, 2556-46-9; Zc, 622-15-1;
3a, 33821-87-3; 3b, 33821-84-0; 3c, 96807-23-7; 3d, 61201-42-1; 3e, 6120143-2; 4a, 96807-24-8; 4b, 96807-25-9; 4c, 96807-26-0; 5a, 96807-27-1 ; 5b,
96807-28-2; 5c, 96807-29-3; 5d, 96807-30-6; 5e, 96807-31-7; 5f, 96807-32-8;
6 , 4903-40-6; 7, 96807-33-9; 8 , 96807-34-0: Ph,C=C=O,
525-064;
MelC=C=O, 598-26-5; H 2 C 0 , 50-00-0; (F,C)>CO, 684-16-2; (EtOCO)KO,
609-09-6.
[l] Review: W. Friedrichsen, T. Kappe, A. Bottcher, Hererocj~c/e.?19 (1982)
1083.
[2] H. Gotthardt, K:H. Schenk, Tefrahedron Lett. 24 (1983) 4669.
[3] K. T. Potts, M. Sorm, J. Org. Chem. 37 (1972) 1422.
[4] A. Stock, H. Stoltzenberg, Ber. Dfsch. Chem. Ges. SO (1917) 498.
[5] T. Kappe, W. Lube, Monarsh. Chem. 102 (1971) 781.
[6] 7: 81%, m.p. 232-233°C (decornp.); I R (KBr): v = 1645 c m - ' (C=O).
[7] 4 a : IR (KBr): v = 1729, 1695 (C=O), 1646 c m - ' (C=C); ' H NMR (90
MHz, CDCI,, TMS): 6 = 1.39 (s, Me), 4.77 (s, 4-H), 7.13-7.60 (m, 4 Ph);
"C{'H) N M R (CDCl3): 6=22.05 (Me), 58.24 (C-4), 101.1 1 (C-I), 164.88
(2C=O) and further signals.-4c: 'H NMR (CDCI3):S = 1.88 ( s , Me),
2.02 (s, Me), 4.85 (s, 4-H), 6.65-7.28 (m, 3Ph).
[El R. Huisgen, H. Gotthardt, Chem. Re) I01 (1968) 1059.
[9] R. Huisgen, Acc. Chem. Res. I0 (1977) 117.
[lo] Cf., e.g.: R. Huisgen, P. Otto, Tefrahedron Left. 1968, 4491; D. Borrmann in Houben-Weyl-Miiller: Merhoden der organischen Chemie, Vol.
V11/4, 4th ed., Thieme, Stuttgart 1968, p. 53.
[ I I] R. B. Woodward, R. Hoffmann, Angew. Chem. 81 (1969) 797; Angew.
Chem. I n [ . Ed. Engl. 8 (1969) 781.
[I21 5a: I R (KBr): v = 1731, 1699 c m - ' (C=O); ' H NMR (CDCI,): fi=4.05
(t. J=1.65 Hz, CHz-CH), 4.60 (d, J = 1.65 Hz, CH2-CH), 6.73-7.27
(rn. 3Ph); MS (70 ev): m / z 370 ( M + , 4%).-5b: 'H-NMR (CDCI,):
6=l.51 (s, Me), 4.02 (s, CH2), 6.52 ( s , 1-H), 7.30 (mc, 2Ph).-5c: ' H
NMR(CDCI,):6=1.23(s,Me),1.52(s,Me),4.13(s,CH2),7.12~7.62(m,
2Ph); '3C{'H} N M R (CDCI,): S=9.69 (Me), 22.62 (Me), 52.13 (C-4),
67.73 (C-3), 99.12 (C-I), 169.23 (2C=O) and further signals.-8: 89%,,
m.p.=149.5-151"C; ' H N M R (CDCI,): b= 1.10-2.10 (m, XH), 1.43 (s,
Me), 2.82-3.10 (m, NCH), 3.91 (s, OCH2), 4.26-4.50 (m, NCH), 6.907.43 (m, Ph).
[I31 5d: I R (KBr): v = 1745, 1718, 1709 c m - ' (C=O); ' H NMR (200 MHz,
CDCI,): 6=1.39 ( s , Me), 1.78 (s, Me), 7.16-7.58 (in, 2Ph): "C('H)
N M R (CDC13): S=9.04 (Me), 22.28 (Me), 55.63 (C-4), 99.30 (C-I),
122.03 (4, Jc,=291.4 Hz, 2CF3), 165.04 (2C=O) and further signals;
MS (70 ev): m / z 458 ( M + , 3%).
1141 5e: IR (KBr): v = 1768, 1745, 1712 c m - ' (C=O); 'H NMR (CDCI,):
6=1.24 (t, J = 7 . 1 Hz, C H ~ - C H I ) , 1.77 (s, Me), 4.31 (q. 5=7.1 Hz,
CH,-CH,), 6.67 ( s , IH), 7.41 (mc, 2Ph); "C{'HJ N M R (CDCI,):
6=9.79 (Me), 13.80 (2Me), 58.45 (C-4), 63.12 (20CH2), 81.36 (C-3),
94.45 (C-I), 164.19 (2C=O), 165.19 (2C=O) and further signals; MS (70
eV): m / z 452 ( M + ,35%).
0 VCH Verlagsgesellschaf, mbH, 0-6940 Weinheim, 1985
0S70-0833/85/0707-0609 $ 02.50/0
609
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dihydro, pyrimidinium, carbonyl, compounds, cycloadditions, first, ketene, olates, oxo, othet, dipolar
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