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Asymmetric Nucleophilic Acylation via Metalated Chiral Amino Cyanides Enantioselective Synthesis of 3-Substituted 4-Oxoesters by Asymmetric Michael Addition.

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for 2a, b, 38 h at 100"C in 30 mL of NEt, with 250 mg of (Ph,P),PdCI,, 250 mg
of CuI. and 500 mg of Ph,P; for la, c, 180 and 43 h, respectively, in 20 mL of
NEt, with 100mg of (Ph,P),PdCI,, 100mg of CuI, and 250 mg of Ph,P).
Workup was performed by treating the reaction mixture with petroleum ether
(PE, b.p. 30-70°C) or ether, followed by filtration. The filtrate was washed
with 2 M hydrochloric acid as well as with saturated aqueous sodium chloride
solution, dried over magnesium sulfate, filtered, and evaporated to dryness
under vacuum. Products la-c were purified by flash chromatography on
100 mL of silica gel 60(E.Merck, 230-400mesh; eluent PE/ethyl acetate (EE)
lOO/l) and repeated crystallization from acetone and heptane. The
triphenylenehexaynes 2 a, b were each purified by column chromatography on
400 mL of silica gel 60 (E.Merck, 70-230mesh; eluent PE/EE lOO/l) and
subsequent recrystallization (2a, 2 x from acetone, 1 x from heptane, 3 x from
acetone containing 30% 1,2-dichlorobenzene, and 6 x from acetone; 2b, 1 x
from acetone containing 30% 1,2-dichlorobenzene and 20 x from acetone).
The phase transition data were obtained by polarizing microscopy (PM, Leitz
Laborlux 12 Pol with a Mettler FP 82 hot stage, usual rate of heating
1 K min-') and by DSC (Mettler TA 3000/DSC 30 S and Graphware TA 72,
usual heating rate 5 K min-I).
The hexaynes 1 and 2 described here are multimorphic in the solid phase with
reproducible solid/solid transitions and/or form4epending o n the thermal
history of the sample-metastable modifications. The value given as the melting
point refers in each case to the highest-melting crystal modification; if necessary. !his modification was obtained by suitable thermal pretreatment of the
samples (e.g., annealing or a second heating). K = crystalline, N, = nematicdiscotic. I = isotropic phase.
Hexakis[(4-pentylphenyl)ethynyl]benzene1 a (C,,H,,, M , = 1099.7): Yield
46%. yellow crystals from heptane, m.p. (K + N,) = 169.5'C (PM), 170.4"C
(DSC. AH = 44.1kJ mol-I), clearing point (N, + I ) % 187'C (PM, owing to
the strong tendency of this compound to decompose, only an approximate
transition temperature could be measured. after determining the rough transition temperature, a fresh sample was placed in the hot stage at a temperature
just below this value and the sample was heated at 10K min-I), 184.9"C (DSC,
AH = 0.2kJ mol-'. heating rate 10 K min-I). IR (CCI,): V [cm-'1 = 2220
(C-C) UVjVlS (Cary 118,hexane): L,,, [nm] (Ig E ) = 373 (sh, 4.946). 350
(5.199).'H NMR partial spectrum (Bruker WH 400,CDCI,): 6 = 7.6and 7.2
(2d, 'J(H,H) z 8 Hz each; phenyl H ortho and meta to C-C); 2.6 (t,
'J(H.H) = 7.5Hz; a-CH,), 1.7(tt, ,J(H,H) = 7.5Hzeach; B-CH,). I3C NMR
(Bruker AM 270.off resonance, CDCI,): 6 = 143.89(s; phenyl C-CH,), 131.83
and 128.48(2d ; 2 x phenyl CH each), 127.37 and 120.66 (2s; 2 x phenyl
C-C-C).99.42and87.20(2s;C-C),35.99,31.50,30.88,22.52,and13.98(4t.
1 q; pentyl C) 1 b, c were obtained analogously; their spectra are in good
agreement with those of 1 a.
Hexakis[(4-hexylphenyl)ethynyl]benzene 1 b (C,,H,,,,
M , = 1183.8): Yield
57%. yellow crystals from acetone, m.p. (K N,) = 123.7"C (PM), 124.4"C
(DSC. AH = 38.9kJ mol-I), clearing point (N, t I) = 142.0"C (PM).
142 9 C (DSC, A H = 0.2kJ mol-I).
Hexakis[(4-heptylphenyl)ethynyl]benzene 1 c (C,,H,,,, M , = 1268.0): Yield
52%. yellow crystals from acetone, m.p. (K + N,) = 98.2"C(PM), 99.0"C
(DSC. A H = 44.4kJ mol-I), clearing point (N, + I) = 131.2"C (PM),
132.6 C (DSC, A H = 0.4kJ mol-I).
2,3,6.7.10,11
-Hexakis[(4-pentylphenyl)ethynyl]triphenylene 2 a (C,,H,, , M , =
1249.7):Yield 35%. bright yellow crystals from acetone, m.p. (K 4 N,) =
156.2'C(PM). 156.8"C(DSC, AH = 36.7kJ mol-I), clearing point (N, + I)
= 236.6 C (PM, owing to the strong tendency of this compound to decompose,
only an approximate transition temperature could be measured; after determining the rough transition temperature, a fresh sample was placed in the hot stage
at a temperature just below this value and the sample was heated a!
10 K min-'), 237.1"C (DSC, AH = 0.1kJ mol-I). IR(CC1,): V [cm-'1 = 2220
(CE C) . UVjVIS (heptane): A,, [nm] (Ig E ) = 367 (sh, 5.176),345.0(5.370).
314.0(sh. 5.001). 'H NMR partial spectrum: 5 = 8.6(s; triphenylene H), 7.6
and 7.2(2d. 'J(H,H) % 8 Hz each; phenyl H ortho and meta to C=C), 2.6(t,
'4H.H) = 7.8Hz; a-CH,), 1.7 (tt, 'J(H,H) = 7.5Hz each; B-CH,). "C
NMR: 0; = 143.18(s; phenyl C-CH,), 131.99and 128.30( 2 d ; 2x phenyl CH
each), 127.97and 124.77(2s; inner and outer triphenylene C without assignment, 126.67(d; triphenyleneCH), 120.79(s; phenyl C-C=C), 94.62and 88.41
(2s: C=C). 36.04,31.68,30.99.22.64,and 14.13(41, 1 q ; pentyl C). Compound 2 b was obtained analogously; its spectra are in good agreement with
those of 2a.
2,3,6.7.lO.ll-Hexakis[(4-heptylphenyl)ethynyl]triphenylene 2 b (C,08H,20,
M, = 1418.2): Yield 23%, bright yellow needles from acetone, m.p. (K
N,) = 121.3'C (PM), 122.0"C(DSC, AH = 41.1kJ mol-I), clearing point
(N, I ) = 174.8"C(PM), 176.6"C(DSC, AH = 0.1 kJ mol-I).
10.1 I-Hexakis(1-heptyny1)triphenylene (C,,H,,,
M, = 793.2): Yield
14-20%. bright yellow, partly crystalline oil. IR (CCI,): V [cm-'1 = 2235
( C E O . 'H NMR partial spectrum: 6 = 8.5 (s; triphenylene H), 2.5 (I,
'J(H.H) z 7 Hz; C=C-CH,) 1.7 (It, 'J(H,H) % 7 Hz each; P-CH,). I3C
NMR: 6 = 127.96 and 125.35 (2s; inner and outer triphenylene C without
assignment), 126.99(d; triphenylene CH), 95.12and 79.65(2 s; C=C), 31.19,
28.55.22.31,19.77,and 14.01(4t, 1 q ; pentyl C).
10,ll-Hexakis(l-decyny1)triphenylene (C,,H,,, , M, = 1045.7):Yield
13%. bright yellow crystals after flash column chromatography (silica gel 60,
-
--f
-
A n p i Chem. In!. Ed. Engi. 29 (1990) No. 2
0 VCH
heptane/ethyl acetate 150/l), m.p. (K + I) = 37°C (PM), 41.0-C(DSC,
A H = 63.0kJ mol-I). IR (CHCI,): C [cm-'1 = 2235 (CEC). 'H NMR partial
spectrum: 6 = 8.5 (s; triphenylene H), 2.5(t. 'J(H,H) % 7 Hz; CsC-CH,). 1.7
(tt, 'J(H,H) zz 7 Hzeach; P-CH,). "CNMR: 6 = 127.96and 125 37 (2s;inner
and outer triphenylene C without assignment) 126.96(d; triphenylene CH).
95.12and79.66(2s; C-C), 31.91,
29.25,29.07,28.69,22.68,19.82,
and 14.09
(6 t, 1 q. aliphatic CH, and CH,).
Received: August 29,1989 [Z3527 IE]
German version: Angew. Chem. 102 (1990)200
[I]B.Kohne, K. Praefcke, Chrmia 41 (1987)196,and papers of other authors
cited therein.
[2] K. Praefcke, B. Kohne, K. Gutbier, N. Johnen. D. Singer, Liq. Crysf.5
(1989)233.
[3] K.Praefcke, B. Kohne, unpublished results. D. Singer, Drplomurhert F 5 5 ,
Technische Universitat Berlin 1989.
[4] M. Ebert, D. A. Jungbauer, R. Kleppinger, J. H. Wendorff, B. Kohne, K.
Praefcke, Liq. Cryst. 4 (1989) 53.
[51 G. Heppke, H. Kitzerow, F. Oestreicher, S. Quentel, A. Rdnft. Mol. Cr-vsr.
Liq. Cryst. Lett. Sect. 6 (1988)71.
16) R. Breslow, B. Jaun, R. Q. Kluttz, C.-Z. Xia, Tetrahedron 3N (1982)863.
[7]D. Demus, L.Richter: Textures ofLiquid Crystals, Verlag Chemie. Weinheim 1978.
[8]For a discussion of further interesting results on the phase transition
N, + I for compounds having the same type of core as in 1 in comparison
to the N + I transition of calamitic/rod-shaped liquid crystals, see [4]
[9] A measure according to Dreiding models: the distance between the centers
of the first elements of the aliphatic side chains lying in the disc plane (with
respect to 1a-c as well as Za, b, cf. formula).
[lo] B. Kohne, K. Praefcke, Chem.-Zfg.109 (1985)121.
[ll]For known cores in noncalamitic, disc-shaped and thermomesomorphic
compounds, see [l, 21 and references therein.
[12]a) H. Ringsdorf, R. Wiistefeld. M. Ebert, J. H. Wendorff, K. Praefcke. B.
Kohne, Adv. Muter. 2 (1990),in press; b) H. Ringsdorf, R. Wiistefeld.
E. Zerta, M. Ebert, J. H. Wendorff, Angew. Chem. fOt (1989)934;Angew.
Chem. I n t . Ed. Engl. 28 (1989)914.
[13]Compare the following excerpt--which supports our opinion-from J.-C.
Dubois, J. Billard in A. C. Griffin, J. F. Johnson (Eds.): Liquid Crystalsand
Ordered Fluids, Bd. 4, Plenum Press, New York 1984,p. 1054:"Interest in
the D, phase (Note: D, = N,) as a model for the carbonaceous mesophases
[H. Gasparoux, C. Destrade, G. Fug, Mol. Cryst. Liq. Cryst. 59 (1980)
109;5 x 10, tons per year] is understood [C. J. Atkmson, J. R. Landes. H.
Marsh, Br. Polym. J. t 3 (1981)11, but until now no pure discogenic hydrocarbon has been made. This void will be filled later."
1141 J. D. Brooks, G. H. Taylor, Carbon 3 (1965)185;J. E.Zimmer. J. L. White,
Mol. Crysf. Liq. Cryst. 38 (1977)177;S. Otami, i b d 63 (19x1)249.
Asymmetric Nucleophilic Acylation via Metalated
Chiral Amino Cyanides:
Enantioselective Synthesis of 3-Substituted
4-Oxoesters by Asymmetric Michael Addition **
By Dieter Enders,* Peter Gerdes, and Helmut Kipphardt
Since the pioneering work of Huuser et al.[ll in the early
1960s, metalated amino cyanides
have been used as d'
synthonsl3] for umpolung of the classical a' reactivity of
carbonyl compounds141and amines.l5] Examples include the
syntheses of u-hydroxy ketones,I6I amino
and
a-amino ketones!" Compounds A are of particular synthetic value as equivalents of acyl carbanions B, especially since
conjugate additions of A to 1,4-unsaturated ketones," b.
cyanides,"'.
and ester^^'^.'^. ''I have been developed
'
[*I
[**I
Prof. Dr. D. Enders, Dip1:Chem. P. Gerdes, Dr. H. Kipphardt
Institut fur Organische Chemie der Technischen Hochschule
Professor-Pirlet-Strasse 1, D-5100Aachen (FRG)
This work was supported by the Fonds der Chemischen Industrie. We
thank Boehringer Mannheim GmbH, BASF AG, Bayer AG, and Hoechst
AG for donation of chemicals.
Vertagsgeselfschaft mbH, 0-6940 Weinhem, t990
0570-0833/90/0202-0179$02.5010
179
to prepare 1,4-dIcarbonyl compounds.[' Numerous applications of optically active amino cyanides have been published in recent years." 3--231 Surprisingly, however, their
synthetic potential for asymmetric nucleophilic acylation has
Table 1. Oxoesters (R)-6 of high enantiomeric purity prepared by conjugate
nucleophilic acylation.
6
R'
RZ
Overall
yield [%I
zz3 ["I
(neat)
a
CH,
CH,
C,H,
n-C,H,
p-C,H,CI
2-fury1
p-C,H,F
CH,
CH,
n-C,H,
C,H,
CH,
n-C,H,
CH,
69
65
- 566
a
b
c
A
d
e
f
6
hardly been exploited so far. Here we report an efficient
enantioselective synthesis of 3-substituted 4-oxoesters by
asymmetric Michael addition of lithiated chiral amino
cyanides to a$-unsaturated esters (Scheme 1).
In this approach, aldeydes 1 are first allowed to react with
the enantiomerically pure secondary amine (S,S)-3[241
[(S,S)-3.HCI, KCN, H,O, 0°C; 1.3 equivalents R'CHO,
0 "C + room temperature, 3 - 14 h, 90 -98 YO]to give the
epimeric amino cyanides (S,S,R/S)-$ which are then meta-
47-71
%
(€1 - 2
1
51
66
61
71
41.2
+ 28.1
i
62.6
i
18.25
i
93
92
2 95
t 95
t 95
90
296
Configuration [b]
(R)
(9ICI
(R)
(R)
(R)
(R)
( R)
[a] Determined by 'H NMR shift experiments with Eu(hfbc),. [b] The absolute
configurations are based on an X-ray structure analysis of a crystalline adduct,
5, as well as on polarimetric measurement after chemical correlation with compounds of known configuration [25]. [c] (R.R)-3 was used as chiral auxiliary.
As exemplified for 6f (R' =p-C,H,F, RZ = CH,), the
enantiomeric excesses may be determined in a facile and
relatively exact fashion from the 'H NMR shift of the sharp
methoxy singlet of the ester function (Fig. 1). The racemic
oxoester rac-6, required as a reference compound, was pre-
;z
0
IR) -6
ee= 90-296%
H3C CH,
Hz 0
KCN
41
+ 57.2
+ 51.9
ee [%] [a]
O*O
/-
HCl
90 - 98 %
1. E t z O , LDA
2. (€)-2, -1OOOC
3 . NH,CI , HzO
c
R2
( S,S,R/S
IS,5,R, R 1- 5
1 -4
Scheme 1
lated with lithium diisopropylamide in ether. Addition of the
cr,a-unsaturated ester (E)-2 at - 100 "C results in formation
of the partially crystalline, highly diastereomerically pure
Michael adducts (S,S,R,R)d,which, as crude products, are
hydrolyzed without racemization by addition of saturated
copper sulfate solution and tetrahydrofuran as cosolvent.
Distillative or chromatographic workup affords the 3-substituted 4-oxoesters (R)-6 in good overall yields (47-71 YO)and
with high enantiomeric excesses (ee = 90 to 2 96%; Table
1). Up to 91 % of the chiral auxiliary reagent (S,S)-3
may be
recovered from the aqueous phase, after basification, by extraction with ether.
180
a VCH Verlugsgesellschufi mbH, 0-6940 Weinhelm. 1990
pared in each case by a route analogous to that in Scheme 1
with achiral pyrrolidine instead of (S,S')-3. The optical antipodes ( 9 - 6 are correspondingly obtained by using the
enantiomeric auxiliary (R,R)-3 [for example, (R)-6a/(S)-6a].
The absolute configurations given here are supported by
an X-ray structure analysis of a crystalline adduct, 5 g
(R' =p-H,COC,H,, R2 = CH,), and by polarimetric measurement after chemical correlation with known compounds
as well as by the assumption of a uniform reaction mechani~m.['~I
This new procedure of conjugate nucleophilic acylation of
enoates with metalated amino cyanides, which occurs with
0570-0833~90j0202-0t803 02.50iO
Angew. Chrm. Int Ed. Engl. 29 (1990) No. 2
0
6f
--t-d =6
6 =6
Fig. 1. Determination of the enantiomeric excess by 'H NMR shift experiments (methoxy singlet). Samples: 50 mg 6 f + 200 mg Eu(hfbc), In 1 mL
CDCI,. Left: rac-6f. ee = 0%. Rlght: ( R ) - 6 f ,ee 2 96%.
high asymmetric induction, opens a simple route to 3-substituted 4-oxoesters 6 [ 2 6271
, of high enantiomeric purity. Preliminary investigations with other Michael acceptors, such as
a$-unsaturated phosphonates and sulfones, show that the
new method has a wide scope of application.125b1
Experimental Procedure
6 : A solution of ( S , S , R / S ) 4(10 mmol) in 75 mL of ether was added dropwise
to a stirred solution at -78 "C of lithium diisopropylamide (11.0 mmol; prepared from 6.9 mL of a 1.6 N solution of butyllithium in n-hexane and 1.1 g of
diisopropylaminein 25 mL of ether at 0 "C). The reaction mixture was allowed
to warm over 0.5 h to 0° C and then cooled to - 100°C. (a-2(10mmol) was
slowly added to the vigorously stirred solution, which was then stirred for an
additional 1 h, allowed to warm over 2-3 h to - 20°C and worked up with
20 mL of saturated NH,CI solution and 30 mL of ether. The organic phase was
separated, washed with 2 x 10 mL of saturated NaCl solution, dried over
Na,SO,, and evaporated under vacuum. The crude Michael adducts 5 were
hydrolyzed with 20 mL of saturated CuSO, solution and 40 mL of T H F as
cosolvent by stirring at room temperature (2-16 h, TLC monitoring; 5d-f, 3 h,
reflux). Ether (1 50 mL) was then added and the aqueous phase was separated
and extracted with 2 x 50 mL of ether. The combined organic phases were
washed with 2 x 10 mL of saturated NaCl solution and dried over Na,SO,.
After removal of the solvent, the oxoesters (R)-6 were purified by kugelrohr
distillation or flash chromatography (petroleum ether:ether 1: 1). The chiral
auxiliary (S,S)-3 can be recovered (2.0 g, 91 %) by addition of 3 g of K,CO, to
the aqueous phase followed by extraction with 3 x 50 mL of ether.
[lo] a) E. Leete, M. R. Chedekel, G. B. Bodem, J. Org. Chem. 37 (1972) 4465;
b) W. Miiller, R. PreuO, E. Winterfeldt, Angew. Chem. 87 (1975) 385;
Angew. Chem. Int. Ed. Engl. 14 (1975) 357; c) E. Leete, G. B. Bodem, J.
Am. Chem. Sac. 98 (1976) 6321.
[ l l ] a) J. D. Albright, F. J. McEvoy, D. B. Moran, J. Heterocycl. Chem. 15
(1978) 881; b) F. J. McEvoy, J. D. Albright, J. Org. Chem. 44 (1979) 4597,
c) W. E. McEven, A. V. Grossi, R. J. McDonald, A. P. Stamegna, ibid. 45
(1980) 1301; d) H. Schick, F. Theil, H. Jablokoff, S. Schwarz. 2. Chem. 21
(1981) 68; e) 0 . Tsuge, K. Ueno, S. Kanemasa, K. Yorozum Bull. Chem.
Sac. Jpn. 60 (1987) 3347.
[12] For the use of 2-(N-methylanilino)acrylonitrileas a doubly "umpoled"
acetaldehyde, see H. Ahlbrecht, K. Pfaff, Synthesis 1980. 413; H.
Ahlbrecht, M. Ibe, ibid. 1988, 210, and references therein.
1131 a) K. Weinges, G. Graab, D. Nagel, 8. Stemmle, Chem. Ber. 104 (1971)
3594; b) K. Weinges, B. Stemmle, ibid. 106 (1973) 2291 ; c) K. Weinges, G.
Gries, 8. Stemmle, W. Schrank, ibid. 110 (1977) 3098; d) K. Weinges, G.
Brune, H. Droste, Liebigs Ann. Chem. 1980, 212; e)K. Weinges, H.
Blackholm, Chem. Ber. 113(1980) 3098; f) K.Weinges, H. Brachmann, P.
Stahnecker, H. Rodewald, M. Nixdorf, H. Irngartinger, Liehigs Ann.
Chem. 1985, 566; g ) K. Weinges, U. Reinel, W. Maurer, N. Gissler. ibid.
1987, 833.
[I41 S. Yamada, S. Hashimoto, Chem. Lett. 1976, 921.
[15] K. Hiroi, K. Nakazawa, ibid. 1980. 1077.
[I61 a) D. Enders in H. Nozaki (Ed.):, Current Trends in Organic Synthesis,
Pergamon Press, Oxford 1983, p. 151; b) D. Enders, H. Lotter, N.
Maigrot, J.-P. Mazaleyrat, Z. Welvart, Nouv. J. Chim. 8 (1984) 747.
[17] D. M. Stout, L. A. Black, W. L. Martier, J. Org. Chem. 48 (1983) 5369.
1181 a) N. Maigrot, J.-P. Mazaleyrat, Z. Welvart,J. Chem. Sac. Chem. Commun.
1984.40; b)J. Org. Chem. 50 (1985) 3916.
1191 a) H. Kunz, W. Sager, Angew. Chem. 99 (1987) 595; Angew. Chem. Int. Ed.
Engl. 26 (1987) 557; b) H. Kunz, W. Sager, W. Pfrengle, D. Schanzenbach,
Tetrahedron Lett. 29 (1988) 4397.
[20] a) J. L. Marco, J. Royer, H.-P. Husson, Tetrahedron Lett. 26 (1985) 3567;
b) Synth. Commun. 17 (1987) 669; c) D. J. Aitken, J. Royer, H.-P. Husson,
Tetrahedron Lett. 29 (1988) 3315.
[21] D. Dopp, M. Pies, J. Chem. Sac. Chem. Commun. 1987, 1734.
1221 A. Delgado, D. Mauleon, Synth. Commun. 18 (1988) 823.
[23] E. Zeller, D. S. Grierson, Heterocycles 27 (1988) 1575.
[(S,S)-3]
[24] (4S,5S)-( )-2,2-Dimethyl-5-methylamino-4-phenyl-l,3-dioxane
may be prepared from commercially available (4S,5s)-( +)-5-amino-2,2dimethyl-4-phenyl-l.3-dioxane
in molar amounts by a two-step reaction
(1) HCO,CH,, reflux, 3d; crystallization (Et,O); (2) LiAIH,, THF, reflux;
overall yield 84%: b.p. 77-8O0C/O.05 Torr, a;' = + 61.8" (neat) [a];' =
+ 46" ( c = 1.5, benzene). (R,R)-3may be obtained analogously: H. Lotter,
Dissertation, Universitat Bonn 1985.
[25] a) G. Boche, D. Enders, P. Gerdes, K. Harms, M. Marsch, H. Ahlbrecht,
H. Sommer, unpublished; b) P. Gerdes, Dissertation. Technische Hochschule Aachen 1989.
[26] Alternatively, the oxoesters 6 may be obtained with high enantiomeric
excess by a-alkylation of (S)/(R)-aminomethoxymethylpyrrolidine hydrazones (SAMP-/RAMP-hydrazones) with BrCH,CO,R: D. Enders, U.
Baus, P. Miiller, unpublished; U. Baus, Dissertation, Universitlt Bonn
1985.
[27] All new compounds gave correct elemental analyses and suitable spectra
(IR, NMR, MS).
+
Received: September 19, 1989 [Z 3552 IE]
German version: Angew. Chem. 102 (1990) 226
[l] a) C. R. Hauser, H. M. Taylor, T. G. Ledford, J. Am. Chem. Soc. 82 (1960)
1786; b) H. M.Taylor, C. R. Hauser, ibid. 82 (1960) 1790, 1960; c) C. R.
Hauser, G. F. Morris, J. Org. Chem. 26 (1961) 4740.
121 Reviews: a) J. D. Albright, Tetrahedron 39 (1983) 3207; b) T.A. Hase
(Ed.): Umpoled Synthons, Wiley, New York 1987.
[3] For d/a nomenclature, see D. Seebach, Angew. Chem. 91 (1979) 259;
Angew. Chem. Int. Ed. Engl. 18 (1979) 239.
[4] Reviews: a) D. Seebach, Angew. Chem. 81 (1969) 690; Angew. Chem. Int.
Ed. Engl. 8 (1969) 639; b) Synthesis 1969. 17; c) D. Seebach, M. Kolb,
Chem. Ind. (London) 1974,687;d) 0. W. Lever, Jr., Tetrahedron 32(1976)
1943; e) D. Seebach, B.-T. Grobel, Synthesis 1977, 357; f) P. Beak, D. B.
Reitz, Chem. Rev. 78 (1978) 275.
[S] D. Seebach, D. Enders, Angew. Chem. 87 (1975) 1; Angew. Chem. Int. Ed.
Engl. 14 (1975) 15.
[6] V. Reutrakul, P. Ratananukul, S. Nimgirawath, Chem. Lett. 1980, 71.
[7] G. Stork, R. M. Jacobson, R. Levitz, Tetrahedron Lett. 1979, 771.
[8] D. Enders, H. Lotter, ibid. 23 (1982) 639, and references therein.
191 a) E. Leete, J. Org. Chem. 41 (1976) 3438; b) G. Sork, A. A. Ozario,
A. Y. W. Leong, Tetrahedron Lett. 1978, 5175; c) H. Ahlbrecht, H.-M.
Kompter, Synthesis 1983,645; d) M. Zervos, L. Wartski, J. Seyden-Penne,
Tetrahedron 42 (1986) 4963; e) M. Zervos, L. Wartski, Tetrahedron Lett. 27
(1986) 2985.
Angen. Chem. Int. Ed. Engl. 29 (1990) No. 2
Synthesis of Tetrachloroammonium Hexafluoroarsenate, NCIFASF? **
By Rolf Minkwitz,* Dirk Bernstein, and Wolfgang Sawodny
is characterized
The chemistry of binary haloamines".
by striking contrasts. Only NF, is thermodynamically stable
(AH" = - 31.44 kcal mol-'13]); even with elemental fluorine, it reacts in the presence of Lewis acids only when energy
is supplied14] to give NFF salts. Pure NCI, (AH" =
54.7 kcal mol-' IS]>, on the other hand, violently explodes
+
[*] Prof. Dr. R. Minkwitz, DipLChem. D. Bernstein
Fachbereich Chemie, Anorganische Chemie, der Universitat
Postfach 500500, D-4600 Dortmund 50 (FRG)
[**I
Prof. Dr. W. Sawodny
Abteilung Anorganische Chemie der Universitat
Oberer Eselsberg, D-7900 Ulm (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0 VCH Verlagsgesellschaft mbH. 0-6940
Weinheim. 1990
0570-083319OjO202-0181$OZ.SO/O
181
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cyanide, asymmetric, oxoesters, michael, amin, enantioselectivity, metalated, chiral, acylation, synthesis, additional, substituted, via, nucleophilic
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