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Oxidation of Metal-Coordinated Thioethers with DimethyldioxiraneЧA New Stereoselective Synthesis of Chiral Sulfoxides.

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clearly not acting as a simple acid catalyst. Since both pathways
involve the localization of a positive charge near the rearranging
C-C bond. the catalytic effect of 62C7 might result from selective stabilization of the charge distribution in the transition
state." 'I The catalytic effect does not change significantly between pH 5 and 8. Stabilization of a positive charge could be
mediated either by a carboxylate with a pK, of less than 5 o r by
aromatic resid~es.['~1
Using electrostatic complementarity to the transition state as
a guiding principle for hapten design, we have developed the
first antibody-catalyzed 1.2-rearrangement of C-C bonds.
Since formation of a transient positive charge in the migrating
bond is a general feature of nucleophilic 1,2-shifts. the same
principle should be applicable to the design of transition state
analogues for other rearrangement reactions. We are now investigating improved haptens containing additional features of the
transition state, such as a cyclopropane moiety which mimics
the geometry of the bond migration.
[Y] J-L. Reymond. K. D. Janda. R . A. Lerner. Angekr Choii. 1991. 10.3. 16YO.
A n g ~ Chet71.
.
1n1. Ed. Engl. 1991. 30, 1711.
[lo] K . B. Wiberg, Chern. Ree. 1955. 5s. 713.
[ I l l V. P. Vitullo. N. Grossman. J. Am. Chem. Soc. 1974. Y4. 3844.
[12] A. R. Becker, D. J. Richardson, J. C. Brown. J. ,4171. Chcrir.Sol. 1977. 99, 505X.
[I31 Other anti-3. anti-4. and anti-5 antibodies might f a i l to catalyze the reaction
because they bind intermediate I equally or bettcr than the transition htate.
[14] S. K . Burley. G . A . Petsko. FEBSLerr. 1986,203, 139: M. Levitt. M. F. Perulr.
J. Mol. B i d . 1988. 201. 751.
Esperitnentnl Procedurr
Dedicated to Professor Helmul Werner
on the occasion of his 60th birthriuv
4-Methoxy-2.6-dimethylphenol was obtained in 87 % yield by heating 2.6-dimethylliydi-oquiiione with conc. H,SO, in methanol at reflux [gal. 4-Methoxy-2.6dimethyl[3.5-Dz]phenol(96% D i . 85"/0 yield) was obtained by using D,SO, and
[D Jmethnnol. Treatment with N-hydroxyethyl-4-chloromethylbenzamideand sodium hydroxide in refluxing water gave I ( 2 . 5 % ) [Xb]. and the 0-alkylation (38%)
a n d 2-alkylation (25 ?6)products. Compound 1 was purified by preparative HPLC
( > 9 X % purity. reverse-phase C-18.H,WCH,CN gradient). 1. M.p.130.0131.0 C : ' H N M R (500 MHz. CDCI,): 6 =7.66. 7.16 (?d. ' J = X.2 Hz. 2 x 2 H ) .
(I X8 (t. '.I = 5.3 H I . I H ) . 6.45 ( s . 2H). 3.78 (1. ' J = 4.7 Hz. 2H). 3.58 (dt.
' J = 4.7 H r . 5.3 Hz, 2H). 3.15 (s, 3H). 2.97 (s. 2H). 1.84 (s. hH): " C N M R
( 1 2 5 M H ~CDCI,):
.
0 =1864. 168.3. 145.4, 139.5. 137.9. 132.5. 130.8. 126.5. 75.4.
62.1, 52.X. 46.3. 42.7. 15.8. 15.7
2 . M.p. 1 4 7 0 14X.0 C: ' H N M R (500MHz. CD,CN): (5 =7.66. 7 16 (2d,
Oxidation of Metal-Coordinated Thioethers
with Dimethyldioxirane-A New Stereoselective
Synthesis of Chiral Sulfoxides**
Wolfdieter A. Schenk,* J u r g e n Frisch,
Waldemar Adam,* and F r a n k Prechtl
Enantiomerically pure sulfoxides RS (O)R' play an eminent
role as intermediates and final products.['] Nucleophilic substitution at diastereomerically pure sulfinic acid esters or amides is
especially suitable for their synthesis;[21the stereoselective oxidation of prochiral thioethers is another attractive method.
When microorganisms o r isolated enzymes are employed, high
expectations regarding yield and selectivity are often not fulHowever, oxidation of alkyl aryl sulfides with enantiomerically pure o x a ~ i r i d i n e sand
l ~ ~ especially with tBuOOH in
the presence of asymmetric titanium catalysts, methods devel'J=X.3Hr.2~2H).7.08(b~.lH).6.67(~.lH).5.64(~,lH).4.03(~,2H),3.70(~,
oped by Kagan et al.[51and Uemure et al.['' are well proven.
3H). 3.5Y(m. 3H). 3.41 (m, ZH),3.15 (t, ' J = 4.5 Hz. 1 H ) . 2.21. 2.06 (2s, 2 x 3H);
" C NMR (135 MHz. CD,CN): 6 =168.6, 152.1, 147.6. 146.2. 132.8. 129.1. 128.0,
Dialkyl sulfides. on the other hand, are generally oxidized with
126.1. 125.7. 123.X. 112.0, 61.6. 56.6, 43.1. 32.2. 17.0. 12.9.
only poor enantio~electivity.[~-'~
We report here on a new
~
in lOOmM NaCI. 5 0 m ~
Assay conditions: 5 0 - 1 5 0 0 p ~substrate 1, 8 p antibody
methodology for solving this selectivity problem. The prochiral
either bis-tris(bis(hydroxyethyl)~minotris(hydroxymethyl)meth~~ne)
or 1,3-bisthioether is first coordinated to an enantiomerically pure transi[tris(hydroxymethyl)methylamino]propane.37 "C. Product formatron was followed
tion metal complex fragment, which is then oxidized with a
by reverhe-phase HPLC (Vydac C-18 21XTP54, 0.45 x 22 em. 1.5 mLmin-'.
lR(l) = 5 02 min. I&?) =7.14min: 28% CH,CN. 72% H,O. and 0.1 "h
reactive oxygen transfer reagent.
CF,COOH). The pD (98% D 2 0 ) values were obtained by adding 0.4 to the pHIt has been known for some time that the three-coordinate
electrode reading.
sulfur in thioether complexes is still susceptible to electrophilic
attack, for example, by [Me,0]+.[71Dimethyldioxirane (DMD)
Received: March 28, 1994 [Z68071E]
German version: Angew. Chem. 1994, 106. 1694
has proven to be an exceptionally effective. predominantly electrophilic oxygen transfer reagent,[*] which can also be used in
the oxidation of organometallic substrates.['1 Therefore. we first
[ I ] a ) R . A. Lerner. S. J. Benkovic. P. G. Schultr. Science 1991.25, 659-667: b)
tested whether the readily available thioether complexes 1 a, b
P. G. Schultz. R . A. Lerner, A c t . Chern. Re.s. 1993. 26. 391.
121 D. Hilvert, A u Cl7wr. Rfr. 1993. 26, 552.
and 2a, b can be oxidized by D M D in acetone (Scheme 1 ) . [ l o 1
[3] a) D Hilvert. K. W. Hill. K . D. Nared. M.-T. M. Auditor. J. Am. Cheni. Soc.
Indeed, the sulfoxide complexes 3a. band 4a. b were obtained in
1989. 111. 9261, b) A . C Braisted. P. G. Schultz. ;hid. 1990. 112. 7430: c) V. E.
high
yields. The identity of the products was established spectroGrouverneur, K. N. Houk, B. de Pacual-Teresa. B. Beno. K. D. Janda, R. A.
scopically and by independent synthesis. By crossover experiLerner. Science 1993. 262,204.
[4] a ) D. Hilvert. K . D. Nared, J. Ani. Cheni. Soc. 1988, 110, 5593; b) D. Y.
ments it was shown that the reaction does not proceed according
Jackson, J. W. Jxcobs. R. Sugasawara,S. H. Reich, P.A. Bartlett. P. G. Schultz,
to the following reaction sequence: a ) dissociation of the
ihid 1988. 110. 4841; c) D. Y. Jackson, M. N. Liang. P. A. Bartlett. P. G.
thioether. b) oxidation of the uncoordinated thioether, and c)
Schultz. . 4 i r , ~ y i .C'heni. 1992, 104. 196: Angeii'. Chern. I n / . Ed. Erigl. 1992. 31.
coordination of the resulting sulfoxide. Thus, oxidation of an
182, e ) A. C. Braisted, P. G. Schultz. J Am. Chr.m. Six 1994, 116, 2211.
[5] a ) C L e n s T. Kramer. S . Robinson, D. Hilvert, Scimce 1991. 253, 1019: b) J.
A. Abhley, C:H. L. Lo, G . P. McElhaney, P. Wirshing. K. D. Janda. J Arn.
C'ht,rii Srtc. 1993. 11s. 2515.
161 For ecneral discussion. see' J March, Advunt.rd Orgrmn Chemisfr),.4th ed.,
Wiley. N e w York. 1992, pp. 1051 - 1 156.
[7] For review. see: B. Miller, Acc. Chern. Res. 1975. 8, 245: applications: R.
Cassir. M. Scholz, R. Tapia. J. A. Valderrama. Zwcihdron Letr. 1985. 26.
6281. F. M. Hauser. K.-H. Park, J. Org. Chern. 1978,43,113: S. M. Kupchan.
C:K. Kim. K . Miyano. Hc,terocw/es 1976,4. 235: U. Eder. G. Haffer. G. Neef.
K . Prerewowsky, G . Sauser. R. Wiechert. Chem. Ber. 1978. lit. 939: D. J.
Hart. A. Kim. R. Krishnamurthy, G. H. Merriman, A. M. Waltos. Terrohedron
1992. 48. 8179.
[8] a ) H . Greuter. H. Schmid, Hch. C'hirn. Acta. 1972,SS. 2382: b) J. Borgulya. R.
Madeja. P. Fahrni. H. J. Hansen. H. Schmid. ihid.. 1973. 56. 34.
['I
[**I
Prof. Dr. W. A. Schenk, DipLChem. J. Frisch
Institut fur Anorganische Chemie der Universitit
Am Hubland, D-97074 Wurzburg (FRG)
Telefax: Int. code +(Y31)888-4605
Prof. Dr. W. Adam, Dr. F. Prechtl
Institut fur Organische Chemie der Universitit
Am Hubland. D-97074 Wurzburg ( F R C )
Tekfdx: Int. code +(931)888-4606
Sulfur(1v) Compounds as Ligands. Part 21. This work was supported by the
Deutsche Forschungsgemeinschaft (SFB 347 "Selective Reactions of MetalActivated Molecules") and thc Fonds der Chemischen Industrie. Part 20:
W. A. Schenk. A. Khadra, C. Burschka, J Orxunomet. Chuni. 1994. 468. 75.
COMMUNICATIONS
I
P h L R ~
cPp/
\cI
R-S-Me,
NH,PF6
Ph2
Ph2
1'
I
Ru
fp>
\"
S-Me
PF6-
I
R
Ph2
1'
I
Scheme 1. 1 a 4 a : R = Ph: 1 h-4h. R = CH:Ph. The bidentate phosphane ligand
is bis(dipheny1phosphino)methane (dppm) in 1 and 3. and bis(dipheny1phosphino)ethane (dppe) i n 2 and 4.
equimolar mixture of 1 a and 2 b with DMD gave the sulfoxide
complexes 3a and 4 b . No crossover products 3 b and 4 a were
formed. Similarly only 3 b and 4a were obtained from a mixture
of I b and 2a. and no detectable amounts ( 2 2 % . 31PNMR
spectrum) of the crossover products 3a and 4 b were found.
rotation for 7 c indicates an R configuration by analogy with
(S)-MeS(0)nPr ([all,
= - 139) and (R)-MeS(0)iBu ([%ID =
+ 138).C2"1
The high diastereoselectivity of the oxygen transfer is kinetic
in origin. The sulfur atom in thioether complexes usually undergoes rapid pyramidial inversion;"'] for example, only at
-4O'C can separate NMR signals be observed for the two
diastereoisomers of 5b, which are nearly equal in energy (18 %
de). Each diastereoisomer can exist as three different rotamers
with respect to the Ru-S bond. According to the NOE difference spectra (NOE = nuclear Overhauser effect; irradiation
of the Cp resonance frequencies causes comparable enhancement of the SCH, and SCHz signals for both diastereomers of
5 b ) . the energetically preferred rotamer is that with both substituents at sulfur oriented towards the cyclopentadienyl ring. In
this orientation, the lone pair at sulfur is sterically shielded by
the aryl groups of the cheiating phosphane."21 As a result, the
oxygen atom must be preferentially transferred to one of the
other two rotamers of (Rs)-5b. The diastereoselectivity of the
oxidation therefore depends on the difference in energy between
the two higher energy rotamers. which were not observed in the
NMR spectra, as well as on the difference in their reactivities.
Since a large number of C,-symmetric bidentate phosphane ligands are known, many of which are commercially available, our
results open up a novel route for the enantioselective oxidation
of thioethers.
Experimental Procedure
All experiments were carried out with purified solvents and under an inert atmosphere. "I' NMR hpectra were recorded at 162 MHz in [DJacetonc at 25 C. usinp
X 5 % H,PO, as the reference.
5
6
Scheme2 5a. 6 a R
=
Ph. Sh, 6 b R = CHLPh. 5c. 6 c R = iPr
The oxidation with D M D can be applied without problems to
the (S,S)-chiraphos (chiraphos = 1,2-dimethyl-l.2-ethanediylbis[(diphenyl)phosphane]) complexes 5 a-c (Scheme 2). The
sulfoxide complexes 6a-c were thus obtained in nearly quantitative yields. and their identity was corroborated by independent synthesis from [CpRu{(S,S)-chiraphos)Cl].
(R)-7
a
Ph
27(+)
b
CH,Ph
s1 ( + )
299 (-1
c
iPr
93(+)
7(-l
(S)-7
73(-)
Scheme 3
The bound sulfoxides were decomplexed in quantitative
yields with sodium iodide in acetone. The chiral metal fragment
was recovered in a form which would allow it to be recycled
(Scheme 3). Separation of the sulfoxides by HPLC on a chiral
column confirmed the diastereoselectivities determined by
NMR spectroscopy and the stereospecificity of the cleavage
reaction. Thus. for example, enantiomerically pure (S)-7 b was
obtained from (Rs)-6b with retention of configuration at sulfur.
and 7bCza1
follow from the
The absolute configurations of 7aC5"I
sign of the specific rotation. The positive sign of the specific
L. 2 : A solution of0.25 mmol [CpRu (dppm)CI] or [CpRu(dppe)Cl]. 50 mg NH,PF,,
(0.30 mmol). and 1 .OO mmol thioether in 10 mL of methanol was heated for 3 4 h
under reflux. The mixture was then concentrated to dryness and the residue recrystalliLed twice from dichloromethane,diethyl ether. The products were thus obtained
;IS yellow crystalline powders in about 90% ( I a, h) and 75% @a, b) yield (correct
elemental analyses). l a : M.p. 173-175 C : "P N M R : 6 = 7 7. Ih: M.p. 192197 C: "P NMR: i)= 8.8. 2a: M p. 164 167 C : "P N M R : 6 = 7 3 7. Zh: M.p.
218-220 C: "P N M R : d=72.8.
3 . 4 : a ) The independent synthesis of 3 and 4 was achieved by an analogous procedure starting from the chloro complex and sulfoxide in 80 8 5 % yield. b): To a
solution of 0 15 mmol thioether complex in 3 mL of acetone at 0 C was added
sloml) ii solution of0.60 mmol DMD in acetone[l0]. After45 min all voIotiIes were
removed under vacuum and the residue recrystallized from acetone:diethyl ether.
The products were thus obtained as light yellow crystalline powder? (correct elemental analyses) in yields >90%. No thioether complex could be detected in the NMR
.p. 120-124 C: "P N M R : 6 = 8.5. 5.0, J
spectra of the crude products. 3
(P.P) = 8 5 HL. 3h: M.p. 214-217
' P N M R : 6 = 8.0,7.7, J ( P . P ) = 8 5 Hr. 4 a :
X 4 . p 171 175 C : " P N M R : 6 =
69.9. J(P.P) = 20 H z . 4 b : M.p. 362-165 C:
."P N M R : 0=73 6. 72.9. J ( P . P ) = 22 Hr.
nthesis w'as achieved following the procedure given for 1 and 2: the prodobtained as yellow crystalline powders in > 95% yield (correct elemental
. Sa: M p. 148 153 C. "P N M R . 6 = 82.1. 63.8. J (P,P) = 41 Hr. Sb:
M.p. 212-217 C. " P NMK. 6 = 82.2. 66.X. J (P.P) = 4 0 H / . SC: M p. 187189 C: "P N M R : 0 = Xi..4. 64.3. J (P.P) = 41 Hz.
6: a ) The indcpcndent qnthesis was achieved starting from the chloro complex and
sulfoxide and following the procedure given for I and 2, 6a-c were thus obtained
as pale yellow crystalline powders i n X5-90'X yield (correct elemental analyses).
(RS)-6a:(Ss)-6a = 93:7 ( 8 6 % d c ~ ) : (R,)-6a: "P N M R : 6 = 81.8, 60 3. J (P.P)
=36 Hr: (Ss)-6a: "P N M R : 6=79.1. 62.3, J (P.P) = 36 HL. IKS)-6h: (S&
6 b = 5 0 : 5 0 ( 0 %L).( R S ) - 6 b "P
. NMR: d = 80.9. 61.2. J(P.P) = 37 Hz: (Ss)-6b:
"P N M R : 6 = 80.9. 61.8. J (P.P) = 36 Hr. ( R , ) - ~ c :(Ss)-6c = 12:88 (76"% d e ) .
RS-6c: "P N M R - 0=78.6. 60.4. .I (P.P) = 37 HL; ( S - 6 ~ )"P
: N M R : 6 = 80.6,
57.X. J(P.P) = 37 Hz. h ) The oxidation o f 5 a - c to 6a-c with DMLI \bas carried out
as described above. The extent of reaction and the diastereoisomeric ratios u'
determined from the N M R spectra o f t h e crude reaction mixtures. 6a: Yield 95'
(K,)-ha. (Ss)6a=73.27 (46°C h).6 b : Yield YO
,)-6h: (S,)-6b 2 Y Y : I (98
& ) . 6 c : Yield 95%. (R,)-6c: (SS)-6c=7:93 (86
K i w i o w / of /lie . s i i l / o 4 i a . The sulfoxide complex (0.10 mmol) and 75 iiig sodium
iodide (0 50 mmol) were heated for 15 h under reflux in 5 mL of acetone. The
mixture was then concentrated. The residue w a s taken up into 2 m L of
dichloromethane a n d chromatographed on silica. [CpRiil(S.S)-chiraphos)I] was
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eluted lirsr with dichloromethane and then the sulfoxide with acetone. Upon removal of thc solvent. the product was obtained in pure form and in quantitative
yield (h'MR). The eiiantiomenc ratio was determined by HPLC (Chiracel OD
column. hexane;Z-propanol 9: 1. UV and optical rotation detector).
+
MeN02, RT, 44 h
Received- December 2. 1993
Revised version: March 3. 1994 [Z6532IE]
German version: Anjirw. C%eni. 1994. 106. 1699
[ I ] a ) T. Durst i n C'i,iiipr(~//orrti~e
Orguiii< C h ~ m i . s t rCbl.
~ ~ .3 (Eds.: D. Barton. D.
Ollir). Pergamon, Oxford, 1979. p. 121: b) G. Solladie. S~,nfhc.\ir1981, 185;
c ) G H.Posner. .4(c. Clirm. Res. 1987,20. 72: d) The Chrinolr:1.of Sulfoiic.!und
S i i ! / o ~ u k(Eds.:
~~
S. Patai. Z. Rappoport, C. Stirling), Wiley, New York, 1988;
c) ti. K. Andersen in [Id]. p 5 5 : f) G. H. Posner in [Id], p. 823.
[2] a ) K . K Andersen. B. Bujnlcki. J. Drabowiu. M. Mikolajczyk. J. B. O'Brien,
J. O r ~ y .C h ~ i i i 1984, 49. 4070: bj F. Rebiere. 0. Samuel. L. Ricard. H. B.
tia@iin. ihid. 1991. 56. 5991: c) D. A. Evans, M. M. Faul. L. Colombo. J. J.
Bisnhn. J. Clardy. D. Cherry. J. h i . Chcwr. So<. 1992. 114. 5977: d) I. Fernandsz. K. Khiar. J. M . Llero. F. Alcudia. J. Org. Chmr. 1992.57. 6789.
[3] H. L Holland. C ' h m i . RPI.. 1988.HH, 473.
[4] a ) f .A Davis. R. T. Reddy. W. Han. P. J. Carroll. J. Am. Cheni. SOC 1992. 114.
IJ2X. h ) V. Meladinis. U. Verfiirth. R. Herrmann. Z. :V"irur/iirx.h. B 1990. 45.
1 6XV
[5] a ) P. Pitchen. E. Dunach. M . N . Deshmukh. H. B. Kagan. J. A m . Cheni. So<.
1984. 106. X l X X : b) H . B. Kagan, F. Rebiere. 0 . Samuel. Phosphorus Sulfirr
Sr/f< Rr!irr. Eleirr. 1991.58. 89.
[6] N.Komntsu. 'vl. Hashizume. T. Sugita. S. Uemura, J. Org. C'hmi?. 1993. 58.
4529
[7] a ) R D Adams. D. F. Chodosh. J. Ani. Chrnr. Soc. 1978,100. 812: b) R. D.
Adams. C. Blankenship. B. E. Segmuller, M. Shiralian. ihid. 1983. 105. 4319.
[ X I W. Adam. D. Golsch, Aiige~l..Ckcni. 1993. 105, 771: Angebt. Chem. Iut. Ed.
O i g ! . 1993.32. 737. and references therein.
[Y] a ) S Wolouicc. J. K.Kochi. Inorg. C/iem. lY9I. 30. 1215: h) W. A. Schenk. J.
Frisch. W. Admi. F. Prechtl, ihid 1992. 31. 3329: c ) W. Adam. U. Azzena. F.
Prechtl. K . Hindahl. W. Malisch. C h w ~B. w . 1992. 125. 1409: d ) A. Perez-Encabo. S. Perrio. A. M. 2.Slawin. S. E. Thomas. A. T. Wierrchleyski. D. J.
Williams. J. C'htw. Soc. CIIEII?.
C o n i i i i r r n . 1993. 1059: e ) M. C. Fermin. J. W.
Bruno. J. .4w. Chein. Sw. 1993,115, 7511
[lo] W. Adam. 1. Bialas. L. Had,iiclrdpoglou.Cliciii. Ber. 1991. 124. 2377.
[I I ] E. W Ahel. K. G. Orrell. S . K. Bhargava. Prog. I i i o r x . Cheni. 1984. 32. 1.
1121 a).l I Sreman. S . G . Davirs. J. C%riii. SIX C h m Conrnrurr. 1984. 1019;
bj S.C j . Daiie5, J. I . Seeman, TL~rrr/ie(lriroiiLerr. 1984.25. 1845. c) J. I. Seeman.
Piifc 4 p / d ( . / U W I . 1987. 59. 1661.
H
w
2
Me
a:R=H
b:R=Me
Me-C-CH=CH-Ph
8
Scheme 1. Reaction of benraldehyde (1) with 2a (1 5 YO 3a at 60 "/o aldehyde cower%on) and 2b (30% 3b at 2 5 % aldehyde conversion). RT=room temperature.
a typical experiment, benzaldehyde (l), one equivalent of alkene
2. and the solid Lewis acid catalyst EPZ-10J3' were stirred in
nitromethane for 44 hours at room temperature. From this reaction styrene (3a) (15%) or 8-methylstyrene (3b) (30%) were
obtained; these yields are based on conversion rates of 60 and
25 YO,respectively. At higher temperatures or longer reaction
times. better conversions were obtained ; however, the formation of by-products also increased. As known from the literature.I4' 3a dimerized to (E)-l,3-diphenylbut-l -me. At higher
temperature (lOO°C) indenes 5 a ( < l o / , ) or 5 b (lOY0) and increased amounts of polymeric products were formed
(Scheme 2).
+Me&=CHR 2
-
PhCH=O
x. CHgo,
1
-
PhCH=CHR
+
[MepO]
3
[41
I\
+
PhCH-0-X-
6
f
Acid-Catalyzed Olefination of Benzaldehyde
Henk-Peter van Schaik, Robert-Jan Vijn,
and Friedrich Bickelhaupt *
Olefinations of carbonyl compounds are usually performed
under alkaline conditions. The reaction starts with the nucleophilic attack of a negative carbon atom on a carbonyl group.
This applies to the classical WittigrZ1reaction and its variants.12]
We present here an acid-catalyzed olefination. namely the reaction of benzaldehyde with olefins catalyzed by a solid Lewis
acid. This reaction is particularly interesting not only because of
the acid catalysis. First, it is a one-pot reaction with a surprising.
and t o our knowledge hitherto unknown, reaction mechanism.
Second. in spite of having certain inherent limitations, this reaction is attractive from a preparative point of view because the
carbon atom used for the olefination of the carbonyl group
comes from a simple olefin, that is, from an inexpensive raw
material. The principle of this reaction is shown in Scheme 1. In
F.Bickelhaupt, Drs. H.-P. van Schaik
Schcikundig Laboratorium. Vrije Universiteit
D e Boelelaan 10x3. NL-1081 HV Amsterdam (The Netherlands)
Telel;ix' Int code +(20)6461479
[*] Prof- Dr.
Dr. R-.l. Vijn
DSM Rescdrch B. V.. Department Fine Chemical Intermediates
NL-6160 MD (ieleen (The Netherlands)
.4tijim.
< h ui?. Int.
W . Eiigl. 1994,33. No. 1 5 1 6
(('1
Ph - CH-O-X-
I J
RHC-CMQ
+
-
I
9
l
A:RT
0
8
I
J
B : 100°C
Scheme 2. Postulated mechanism of product formation. X correspmds to the caitilyst EPZ-10.
The. at first glance, surprising formation of 3 can easily be
explained by using well-known mechanistic principles
(Scheme 2). It is assumed that the acidic catalyst X and 1 generate the intermediate 6, which adds to 2 leading to the formation
of 7; this corresponds to the first step of the Prins reaction.''J In
the continuation of the Prins reaction, except for some special
VCH Verlri~.~gesrl/.~chu/r
mbH, 0-69451 Weiirheirn, 1994
0570-0H33,'94~/.515-1611S 10.00
+ 25:O
161 1
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Теги
chiral, stereoselective, oxidation, synthesis, metali, thioethers, coordinated, sulfoxide, dimethyldioxirane, new
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