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Organic Reactions at High Pressure Cycloaddition Reactions of 11-Methylene-1 6-methano[10]annulene.

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The (R,S)-aminal 3 , prepared from glycine methyl ester
hydrochloride, methylamine, and pivalaldehyde,l'"l was
treated with 14 chiral carboxylic or sulfonic acids. In two
cases one of the two possible diastereomeric salts crystallized selectively: the salt from ( -)-2,3 :4,6-di-O-isopropylidene-2-ketogulonic acid [( - )-diacetone-2-ketogulonic
acid] and ( S ) - 3 , and that from (S)-(- )-mandelic acid and
( R ) - 3 . For preparative resolution a single crystallization
with mandelic acid gave enough enrichment so that N-benzoylation and recrystallization of 2 produced the two enantiomers with greater than 98% ee. Mandelic acid is recovered in 95% yield without detectable racemization.
Experimental Procedure
(R.S)-3: Glycine methyl ester hydrochloride (125.6 g, 1 mol) was added to
375 m L o f 8 M ethanolic methylamine (ice-cooled) with stirring. After I5 h at
room temperature, the suspension was concentrated in a rotatory evaporator
(water aspirator). A slurry of the resulting viscous material in 200 mL of
<'H?CI-, was prepared and concentrated three times. A solution of the resldue, pivalaldehyde (235 mL, 1.5 mol, Fluka pract.), and triethylamine
(209 mL. 1.5 mol) in I L of CH2Cl2was then heated at reflux for 10 h with
separation of water. After cooling, the mixture was filtered through a sintered-glass filter and the filter cake was washed with 500 m L of ether. Concentration of the filtrate gave an oil, which was dissolved in 300 mL of
CHIOH. The resulting solution was combined (with cooling and stirring)
with 600 m L of methanol that had been saturated with HCI gas at 0 "C. After
30 min of stirring at 0 "C and 2 h at room temperature, the mixture was concentrated to a syrup, dissolved in 800 rnL of CHIC12, washed with 670 m L of
3 M aqueous NaOH, and then evaporated to glve the crude product 3
(107.5 g, 69%; yellow oil, which crystallizes upon cooling; for characterization of (R.S)-3 see [lo].
Enantiomeric resolution: A mixture of ( R S ) - 3 (70.0 g, 0.448 mol) and
( S ) - (- )-mandelic acid (70.0 g, 0.460 mol) was dissolved in boiling acetone
F a . 170 mL, saturation!). The solution was stirred in order to spread the initially formed crystals in the insulated flask, which was then allowed to cool
slowly ( I n ca. 6 h to ambient temperature), resulting in the separation of the
(R.S)-diastereomeric salt. After 15 h in a refrigerator ( 5 "C), the crystal cake
was pressed and filtered. Drying in vacuo afforded 54.5 g of light yellow, fine
(S)-(+ ) - 2 : A suspension of the (R.S)-diastereomeric salt (54.5 g, 0.177
mol) in 200 mL of CH2C12was shake;; with 92 mL of 2 M aqueous NaOH.
For recovery of mandelic acid, the aqueous layer was acidified with 50%
HLSOI,whereupon the acid crystallized and was filtered off or extracted into
ethyl acetate. The aminal 3 remaining in the CH2C12 layer was N-benzoylated by addition of benzoyl chloride (20.1 mL, 0.173 mol) and 195 m L of I M
NaOH with ice cooling. This afforded 45.8 g of a yellow crystalline material
with [a],, + 107 (c=I, CH2C12).
(R)-(- ) - 2 : The mother liquor from the crystallization above was concentrated (syrup, ca. 0.27 mol of diastereomeric salts) and then dissolved I n
300 mL of CH2C12. The resulting solution was first treated with 2 M NaOH
(140mL) and then with benzoyl chloride (3OmL, 0.26 mol)/l M NaOH
(280 mL) for removal of mandelic acid and N-benzoylation, respectively, as
described above for the (+)-enantiomer. The lumps of brown crystals obtained upon concentration of the CH2C12 phase were recrystallized from
45 mL of ethanol to give 33.6 g of a brownish material with [a],,-109 (c=l,
Further purification of 2 : Each enantiomer was recrystallized twice from
ethanol. Although the crystals were pulverized, the material dissolved only
very slowly in refluxing ethanol (ca. 1.43 mL/g). Finally, the product was
precipitated from a CHzCll solution by addition of pentane and dried for at
least 12 h at 60 "C/O.l torr. This afforded 34.7 g (0.133 mol) of (S)-(+)-2
(60%)) with [a],,+ 127 ( c = l , CH2C12)and 26.4g (0.101 rnol) of (R)-(-)-2
(45%) wirh [ale - 126 (c= I, CHICI?). A sample was recrystallized several
more times and sublimed (135 "C/O.OI torr) to give material with [a][,+ 127.5
and m.p =143-144"C. For spectroscopic data of ( R . S ) - 2 and (R.S)-3 see
19, lo]. The enantiomeric excess of the derivatives was therefore greater than
98% and 99%. respectively.
141 For further methods see 161, p. 697ff.
I51 J. Jacques, A. Colllet, S . H. Wilen: Enantiomers. Racemates and Resolutions, Wiley, New York 1981.
161 J. P. Greenstein, M. Winitz: Chemistry ofrhe Amino Acrds. Wiley, New
York 1961, p 737ff.
171 See ref [I71 in 191; also see: D. A. Evans, E. B Sjogren, Tetrahedron Lett.
26 (1985) 3783; Y. N. Belokon, A. G. Bulychev, S. V. Vitt, Y . T. Struchkov, A. S. Batsanov, T. V. Timofeeva, V. A. Tsyryapkin, M. G. Ryzhov,
L. A. Lysova, V. I. Backhmutov, V. M. Belikov, J. Am. Chem. Soc. 107
(1985) 4252.
[81 U. Schollkopf, Tetrahedron 39 (1983) 2085; U.Schollkopf, U. Groth, M..
R. Gull, J. Nozulak, Liebrgs Ann. Chem. 1983, 1133: U. Schollkopf, Pure
Appl. Chem. 55 (1984) 1799; H. J. Neubauer, J. Baeza, J. Freer, U.
Schollkopf, Lrehigs Ann. Chem. 1985. 1508; M. Grauert, U. Schollkopf,
ihrd. 1985, 1817.
191 D. Seebach, D. D. Miller, S . Muller, T. Weber, Helu. Chim. Acra 68
(1985) 9.
[I01 R. Naef, D. Seebach, Helu Chim. Acra 68 (1985) 135.
Organic Reactions at High Pressure:
Cycloaddition Reactions of
By Frank-Gerrit Klarner,* Barbara M . J . Dogan,
Richard Weider, David Ginsburg, and Emanuel Vogel
The 1,6-methano[IO]annulene route to cyclopropabenzenes"] suggests 1 l-methylene-l,6-methano[
112]as a suitable starting material for the preparation of the
still unknown methylenecyclopropabenzene~31
via cycloaddition of 1 with dicyanoacetylene (DCA) and Alder-Rickert cleavage. However, 1 , unlike the parent 1,6-methano[lO]annulene, exhibits little tendency to react with
DCA.I4' For this reason, we attempted to favor the cycloaddition by increasing the pressure (to 7000 bar). We report
here the partly unexpected results for the reaction of 1
with DCA (Scheme 1).
At normal pressure, reaction of DCA with 1 (60"C, pentane, 24 h in a sealed glass ampule) affords, in addition to
polymers, a 3-4% yield of a crystalline I : 1 adduct
(m.p.= 158"C), which was identified as 2 by its spectral
properties.lS1According to the 'jC-NMR spectrum (cf. Table l), 2 exists in solution as the fluxional rnethylenenorcaradiene-heptafulvene system, 2a/2b, with both components present in similar amounts. The chemical shift of C1,6 (6=73.9, 32°C) of 2 takes an intermediate position between symmetrically substituted methylenecyclopropanes
(e.g., 3 : 6(C- 1,6) = 39.9)"l and heptafulvene (6(C- 1,6)=
138.3).@]To the best of our knowledge, 2a/2b is the first
example of its kind. I n contrast to 2, the DCA adduct of
1,6-methano[1O]annuIene (6(C-1,6)= 38.1) is only present
as a "frozen" norcaradiene, that is, 2a with >CH2 instead
of >C = CH,.""] The similar energy content of 2a and 2b
is presumably due to the fact that the strain energy of the
methylenecyclopropane s u b ~ n i t , ' ' which
is 13.4 kcal/mol
higher than that of cyclopropane, is able to compensate for
the constraining effect of the 1,6-bridge. 2b does not exhiKlarner, Dr. B. M. J. Dogan
Fakultat fur Chemie der Universitat
Postfach 102148, D-4630 Bochum I (FRG)
[*] Prof. Dr. F:G.
Received: December 13, 1985 [Z 1585 IE]
German version: Angew. Chem. 98 (1986) 363
[I] G. Nass, K . Poralla, H. Zahner, Naturwrssenschafren 58 (1971) 603; 1.
Wagner, H. Musso, Angew. Chem. 95 (1983) 827; Angew. Chem. Inr. Ed.
Engl 22 (1983) 816.
121 Malonic ester synthesis: S. P. L.Sorensen, Hoppe-Seyler.s 2. Physiol.
Chern. 4 4 (1905) 448: N. F. Albertson, S. Archer, J . Am. Chem. Soc. 67
(1945) 308; N. F. Albertson, B. F. Tullar, ibid. 67 (1945) 502.
131 Strecker synthesis: A Strecker, Jusrus Liebigs Ann. Chem. 75 (1850) 2 7 :
Bucherer variants: H. T. Bucherer, W. Steiner, J . Prakr. Chem. 140
(1934) 291; H. T. Bucherer, V. A. Lieb, rbid. 141 (1934) 5 .
0 VCH Verlagsgesellschaft mbH. 0-6940 Wernherm. 1986
Prof. Dr. E. Vogel, R. Weider
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, 0-5000 Koln 41 (FRG)
Prof. Dr. D. Ginsburg
Department of Chemistry, Israel Institute of Technology
Haifa 32000 (Israel)
This work was supported by the Minister fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen and by the Fond der Chemischen Industrie. We thank Prof. Dr. H Duddeck and Dr. M . Kaiser.
Universitat Bochum, for the recording of the high-resolution NMR
spectra and the help with their interpretation.
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Angew Chem. I n / Ed Engl 25 11986) No 4
CN 20
Scheme I . I he numbering of the centers is only intended for the assignment
of the spectra.
Table I. Selected spectroscopic data for the compounds 2, 3 , 4, 6 [a], and
dihydro-6 [b].
2 : "C-NMR (20 MHz, [D,]acetone, ' H broadband decoupled, 32°C):
0=73.9 (C-I, 6): 48.2 (C-7, 10); 104.9 (C-12): 115.0 (-CzN); 123.7 and 125.0
(C-2, 3, 4, 5 ) : 134.1 (C-8, 9); 140.3 (=C-CN): 142.0 (C-11)
3 : "C-NMR(100.6 MHz,CD3CN):6=39.9(s,C-1,6):45.8(d,C-2,5,7,
108.0 (I. C-12): 115.3 (-C=N): 136.1 (5, =C-CN); 138.3 (d. C-3, 4, 8, 9);
144.1 ( s , C-I I )
4 : " C ~ N M R(100.6 MHz, [DJacetone): 6=39.0 (s, C-I, 6); 50 2 (d, C-2, 5, 7,
10): 59.4 ( s , -C-CN); 125.0 (s, - C z N ) ; 128.3 (t, C-12): 129.6 (s, C-11);
According to its spectral and chemical properties, the
high-pressure product formed in lower yield was characterized as the symmetrical 2 : 1 adduct 3.15]This adduct is
very sensitive to light; it rearranges to the cage compound
4, partly upon recrystallization in daylight and quantitatively upon short irradiation with a sunlamp.[51The photochemical transformation of 3 into 4 proves that both dicyanovinylene bridges in 3 are in anti position with respect
to the methylenecyclopropane ring.
The structural elucidation of the second 2 : 1 adduct
proved to be more difficult insofar as an X-ray structure
analysis led to no definitive result (presumably on account
of crystallographic disorder).I8I By high-resolution 'H- and
"C-NMR spectroscopy along with the use of homo- and
heteronuclear decoupling and 2 D NMR experiments, it
was possible to assign structure 6 to this adduct,l5]significant parts of which proved to be identical with those of the
trapping product of 1,6-methano[ lO]annulene- 1 I -ylidene
with 1,3-diphenyli~obenzofuran.~~~
The presence of 6 is
also revealed by the reduction with diimine, which gives
the dihydro compound[51(selective hydrogenation at C- 1
and C-2, see Scheme 1).
The 1 : 1 adduct is formed by Diels-Alder reaction, the
question remaining open whether the [IOIannulene or its
norcaradiene valence tautomer serves as the diene partner
of DCA. The low yield of 2, which could not be improved
by high pressure, thus far has not allowed a detailed study
of the thermolysis. Preliminary investigations show, however, that 2 fragments upon heating (130°C in benzene
( I h) or 400°C in a flow system), but, aside from phthalonitrile, mainly phenylacetylene is formed, which is probably a secondary product of the primarily formed methylenecyclopropabenzene.
139.7 (d, C-3, 4, 8, 9)
6 : 'H-NMR (400 MHz, [Dnlacetone):6=3.22; 3.32 (AB spectrum, 12,12'-H,;
J(12,12')= 19.3 Hz); 3.59 (m, 3-H; f(3,4)=2.2 Hz; J(3,IO)= I Hz): 3.83 (dd,
7-H: J(7,8)=6.1 Hz; 5(7,9)=0.9 Hz); 4.43 (d, broad: 10-H: J(9,10)=6.2 Hz:
5(8,10)= 1.2 Hz: J(2,10)=0.8 Hz): 6.00 (d, broad; 2-H); 6.07 (d, 5-H:
J(4,5)=5.6 Hz): 6.14 (dd, 4-H); 6.62 (m. 9-H: J(8,9)=8.5 Hz); 6.73 (m,
(100.6 MHz, [D6]acetone): 6=42.6
(d, C-10;
J(C-H)= 146.9 Hz); 43.1 (1, C-12; J(C-H)= 137.3 Hz); 45.8 (d, C-7:
J ( C - H ) = 139.5 Hz);61.2 (d, C-3; J(C-H)= 154.2 Hz); 63.9 ( s , C-I 1); 64.4
(s, C-6): 113.1: 113.9: 115.0; 116.2 (s, -C=N); 126.2: 131.8; 132.3: 135.7 ( s ,
=C-CN): 129.9 (d, C-5: J(C-H)= 167.9 Hz); 131.5 (d, C-8; J(C-H)= 174.6
Hz): 132.1 (d, C-9; J(C-H)= 176.8 Hz); 135.3 (d, C-2; J(C-H)= 178.8 Hz):
135.9 (d, C-4; J(C-H)= 166.3 Hz); 140.0 (s, C-I)
Dihydro-6: "C-NMR (100.6 MHz, [D,]acetone): 6=27.0 (I, C-2); 36.9 (d,
<-'-I); 43.0: 44.8 (d, C ~ 7 10);
51.0 (1, C-12); 51.2 (d. C-3); 55.5 (s, C-l I ) ; 66.3
(s, C-6): 112.7; 113.6; 115.8; 116.2 (s, -C=N); 129.2; 131.0; 132.6; 134.7 (s,
=C-CN): 129.0: 131.5: 133.1; 139.1 (d, C-4, 5 , 8, 9)
[a] The assignment of the 'H-NMR signals was made on the basis of a COSY
2D NM R spectrum. The coupling constants were determined by double resonance experiments (irradiation of the signals of H-3, H-7, 2nd H-10 with a
second RF field). A NOESY 2D NMR experiment allowed the determination of the spatial proximity of the noncoupled atom H-3 with H-2 and H-I2
(endo) and a "C,'H correlation the C,H connectivities. [b] Hydrogenated on
the centers marked I and 2 in 6 .
bit any significant heptafulvene character, which is understandable since the conjugation of the methylene group
with the cycloheptatriene system is sterically strongly hindered.
When 1 is allowed to react with DCA at high pressure
(7000 bar, 8O"C, toluene, 4 h), two 2 : 1 adducts, which can
be separated by fractional crystallization, are obtained in
the ratio of I : 4 as determined by 'H-NMR spectroscopy
[yields of the isolated adducts: 1 1 and l6%, respectively;
m.p. = 223 "C (dec.) and 242"C, respectively].
Angew Chem. Int. Ed. Engl. 25 (1986) No. 4
In order to elucidate the mechanism of formation of the
2 : 1 adducts 3 and 6 , we showed by reaction of isolated 2
with DCA at 7000 bar that both adducts could arise from
2. The course of the addition of DCA to 2 is apparently
controlled by the valence tautomeric equilibrium 2a ~ 2 b .
As expected, 2a reacts with DCA in a Diels-Alder type
reaction, resulting in the formation of 3. The ease with
which 3 cyclizes photochemically to give 4 is a consequence of the small distance of the cyano-substituted double bonds, which, ac$ording to force-field calculations of
Ermerf8'is only 2.98 A. The unpredictable formation of the
unsymmetrical 2 : 1 adduct 6 can only be explained by the
reaction of 2b with DCA via the intermediate 5 . The initial step 2 b - 5 may be regarded as an [8+2] cycloaddition, which is known to occur in the parent heptafulvene
system."'] That this cycloaddition occurs in the case of the
geometrically unfavorable 2b, however, is surprising. According to the inspection of models, the double bond between C-1 and C-ll of 5 exhibits a torsional angle of almost 90" (anti-Bredt compound). Accordingly, 5 has significant diradical character and apparently takes advantage of the sterically favorable possibility to stabilize itself
by formation of 6 . Examples of such a butadiene-cyclobutene isomerization are known for cis,cis,truns-cycloheptatrienes[t'l and related, extremely strained compounds."''
The preferential formation of the 2 : 1 adducts 3 and 6
upon reaction of 1 with DCA at high pressure is presumably due to the different activation volumes for the compet-
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ing reactions of 2. The bimolecular [4+2] and [8+2] cycloadditions are certain to have appreciably more negative
activation volumes than the monomolecular Alder-Rickert
cleavage.["' Thus, an increase in pressure should enhance
the rate of the association process strongly in comparison
with the dissociation and the former process should dominate. The example described here clearly reveals the different effects of pressure and temperature on the rate of the
reaction, which can result, as shown here, in the formation
of unusual compounds that are not observed under normal
Received: December 16, 1985;
revised: January 28, 1986 [Z 1590 IE]
German version: Angew. Chem. 98 (1986) 344
[ I ] a) E. Vogel, W. Grimme, S . Korte, Tetruhedron Lett. 1965, 3625: b) E.
Vogel, S. Korte, W. Grimme, H. Giinther, Angew Chem. 80 (1968) 279;
Angew. Chem. Inf. Ed. Engl. 7 (1968) 289; c) B. Halton, B. R. Dent, S.
Bohm, D. L. Officer, H. Schmickler, F. Schophoff, E. Vogel, J . Am.
Chem. Soc. 107(1985j 7175; d) reviews on cyclopropabenzenes: B. Halton, Chem. Reu. 73 (1973) 113; W. €. Billups, Acc. Chem. Res. I 1 (1978)
245; B. Halton, Ind. Eng. Chem Prod. Res. Dev. 1980, 349.
[2] a ) E. Vogel, F. Weyres, H. Lepper, V. Rdutenstrauch, Angew. Chem. 78
(1966) 754; Angew Chem. Inr. Ed. Engl. 5 (1966) 732, b) R. R. Andrea,
H. Cerfontain, H. J. A. Lambrechts, J. N. Louwen, A. Oskam, J . Am
Chem. Soc. 106 (1984) 2531.
[3] Derivatives of methylenecyclopropabenzene: B. Halton, C. J . Randall,
P. J. Slang, J . Am. Chem. Soc. 106 (1984) 6108.
[4] For the cycloadditions to 1,6-methano[IO]dnnulenessee: a) E. Vogel,
Spec. Publ. Cliem. SOC.21 (1967) 113; b) P. Ashkenazi, E. Vogel, D.
Ginsburg, Tetrahedron 33 (1977) 1169; 34 (1978) 2167; this work is regarded by D. C. as Part 90 of his propellane series; c) P. Ashkenazi, M.
Peled, E. Vogel, D. Ginsburg, ibid 35 (1979) 1321; d) P. Ashkenazi, M.
Kaftory, D. Ginsburg, Helu. Chim. Acra 66 (1983) 611; e) P. Ashkenazi,
E.Vogel, D. Ginsburg, ibid. 66 (1983) 615.
151 All new compounds were characterized by their spectra ('H-NMR, "CNMR, IR, UV, MS). Table I contains selected data.
161 R. Hollenstein, A. Mooser, M. Neuenschwander, W. yon Philipsborn,
Angew. Cliem. 86 (1974) 595; Angew. Chem. In,. Ed. Engl. 13 (1974)
(71 S. W. Benson: Thermochemrcul Kinetics. 2nd ed., Wiley, New York 1976,
p. 273, 274.
[S] We thank Prof. Dr. 0 Ermer and Dr. J Lex for the crystal structure
investigations and for the force-field calculations (0.E.j.
191 J. Berkowitz Carlton, R. H. Levin, J. Clardy, J . Am. Chem. Soc. 98 (1976)
[lo] W. von E. Doering, D. W. Wiley, Terruhedron I 1 (1960) 183.
1111 W R. Roth, F.-G. Klarner, W. Grimme, H. G. Koser, R. Busch, B. Muskulus, R. Breuckmann, B. P. Scholz, H.-W. Lennartz, Chem. Ber. 116
(1983) 2717.
1121 M. Christl, U Heinemann, W. Kristof, J . Am Chem. Soc. 97 (1975)
2299, and references cited therein.
[I31 For discussions of the activation volumes of retro Diels-Alder reactions
see G. Jenner, M. Papadopoulos, J. Rimmelin, J . Org. Chem. 48 (1983)
3 Ph,P-C-C-CH,
3 6
3 Ph,PCI
I**]This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, Hoechst AG, Knapsack and Frankfurt, and SKW Trostberg.
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mhH, D-6940 Weinhelm. 1986
+ 2 5 + 3 LiCl +
The allene 1 forms colorless crystals with a melting
point (dec.) of 224"C, which are only sparingly soluble in
halogenated hydrocarbons. The allene structural unit is revealed in the IR spectrum by an absorption at 1890 cm-'.
The presence of the isomeric tetrakis(dipheny1phosphino)propyne is also excluded by the observation that the
3'P-NMR spectrum contains only one signal (6= -6.9). In
the I3C-NMR spectrum, the central allene C atom gives
rise to a quintet ('JP,.=9.8 Hz) at 6=209.7; the flanking C
atoms, on the other hand, give rise to a singlet at 6=89.1.
In solution the Ph2P substituents are apparently free to rotate around the P-C bonds (such as in 2, R = Phl2'), so that
only one set of signals results from the eight phenyl
groups. I n the mass spectrum (electron ionization, 70 eV),
the peak at m/z 776 is due to the molecular ion.
The allene 1 can be converted into the tetraoxide 7a by
careful oxidation with bis(trimethylsily1)peroxide in tetrahydrofuran (THF) (87% yield, m.p. =2S8-26O0C); 7a
Prof. Dr. H. Schmidbaur, DipLChem. T. Pollok
Anorganisch-chemisches lnstitut der Technischen Universitat Munchen
Lichtenbergstrdsse 4, D-8046 Garching (FRG)
+ 3 II-C,H,~
3 ?h,P-C-C-CH,Li
By Hubert Schmidbaur' and Thomas Pollok
3 n-C4H9Li
Ph,P \
Little is known about phosphinoallenes at present,"' and
examples with four phosphino substituents ( 1 ) are totally
lacking. Owing to the partly unexpected reaction behavior
of I , Lbis(dipheny1phosphino)ethene 2 , R = Ph,[" -cyclepropane 3, R = Ph,l3' and -methane 4, R = Ph,[41upon quat e r n i ~ a t i o n , ' ~~. ~x]i d a t i o n , " and
complex formation,[*] we
have synthesized the title compound 1 , R=Ph.
Compound 1 was prepared surprisingly easily by lithiation of I-diphenylphosphinopropyne 5l9I to give 6, followed by reaction of 6 with chlorodiphenylphosphane,
and isolated in highly pure form in satisfactory yield
(60%).['"]The molar ratios given in the two reaction equations clearly show that several transmetalations occur. Apparently, the CH acidity of the intermediates increases
with increasing number of phosphino substituents, thereby
favoring the complete replacement of all propyne/allene
H atoms by Ph2P groups. I n contrast, the reactions of lithium or magnesium propynide (Li,C3 and Mg,C3) with
chlorodiphenylphosphane afforded only tetraphenyldiphosphane." 'I
Tetrakis(diphenylphosphino)allene* *
70: X
7b: X
/ PPh,
= S
7 c : X = Se
Table I. Selected NMR and IR data for the compounds I and 7a-c.
"P-NMR (CDCI,), 6 values
"C-NMR (CDCI,), 6 values
c pz
IR v(C=C=C) [em-']
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methylene, reaction, cycloadditions, annulene, organiz, high, pressure, methane
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