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Catalytic Asymmetric CarbonylЦEne Reactions.

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can be produced with stable projectiles and accessible targets.
Spontaneous fission does not yet predominate. Thus, seen
in the light of nuclear stability. the limit of the periodic table is
not yet in sight. This limit will finally be reached when nuclei d o
not hold together at all but immediately break into two fragments.
The process that produce heavy nuclei remain more difficult
to judge. They are not yet well understood, and what is known
about fusion reactions in lighter systems cannot be applied.
Thus. one relies upon empirical extrapolations; the 15 picobarn
production cross section of the nucleus *"I 10 opens exciting
perspectives. of course. The cross section extrapolated for element 112 is about three picobarn, that for element I 1 3 and
element I14 one picobarn."] if zinc-70 ( Z = 30) or germanium76 (;I
= 32) are fused with lead or bismuth- all within reach of
the SHIP group. However. the center of stability, the mountain
lake ;iround element 114. cannot be reached from lead-208. As
shown i n Figure 3, the channel of accessible nuclei goes past to
the west. Other strategies would also not lead to success, because
no combination of accessible projectile and target nuclei would
provide cnough neutrons. Nevertheless. it seems not to be
utopian to step onto the broad western beach. If the landscape
would appear there as predicted, one would also catch a glimpse
of that glorious lake.
German version. Air'qm Chrnr. 1995. 107. 1857 1861
Keywords: element 110 . element 111 . nuclear stability
transuranium elements
[I] G. Munrenberg. Rep. ProX P / I ~ J1988. 51. 57-104.
121 G. Herrmann. Anjieii.. Chrin. 1988. 100, 1471 1491 : -Iii,yoi~C h o n
E i i ~ l 1988.
27. 1417-1436.
S. Hofmann, V. Ninov, E P. HeBbcrger. P. At-mbruster. H. Polger. G.
Mdnzenherg. H. J. Schott. A. G. Popeko. A. V. Ycreiiiin. A. N . Andreyev. S.
Saro. R . Janik. M. Leino, %. P/y.s. A 1995. 350. 277 280
[4] S. Hofmann. V. Ninov, F P. HeBbergcr, P. Armbrustcr, H. Folger, G
Munrenberg, H. J. Schott. A. G. Popeko. A. V Yereinin. A. N. Andreyev. S.
Saro. R . Jmtk. M Leino. G'SI Nuchrirhten 1995 ( 2 ) . J is.
[5] a ) Conference: Loll. Eiiergj. N d ( w f l i ~ n u n n ~St.
~ . ~l'etersburg.
1995. April
18-22: Preprint GSI-9.5-2.5 1995; Proceedings in presr h ) S Hofmann. paper
in [ j a ]
161 S. Holinann. V. Ninov. F. P. Henbcrger. P. Arnihl-tihter. H. Folger. G.
Munrenberg. H. J. SchAtt. A. G. Popeko. A. V. Yereniiii. A. N. Andreyev. S.
Saro, R . Janik. M. Letno, Z. P l i u . A 1995. .W,281 7x2.
171 A Ghiorso. D. Lee. L. P. Soinerville. W. Loveland. J. hl Nitschke. W. Ghiorso.
G . T. Seaborg. P. Wilmarth. R. Leres, A . Wydler. M. Nurmia. K. Gregorich,
R Ga)lord. T. Hamilton. N. J. Hanntnk. D. C . Holl'man. C. Jarryiiski. C .
Kacher, B. Kadkhodayan. S. Kreek. M . Lane. A. Lyoii. M . A. McMahan. M
Neu. T. Sikkeland. W. J. Swiatecki. A. Tiirler. J. T. Waltoii. S. Yashtta. Nircleus. W u d ~ wCo//i\ion\
V (Eds.: M. Di Toro. E. Migneco. P Ptatelli) ( . W w / . P / q s.
A 1995. 583. 861- X66).
[ X I Yu. A. Lararev. paper in [ja]. Quoted from S. Hofmami. pcraonal communication.
[9] J. V. Kratz. Ac/inirLs-Y3 (Ed,: D. L. Clark. D. E Hohiit-l. J Fuger) ( J Aliqrs
Conipd. 1994. -7/3.'2/4,20-27): D. C. Hoffman. C h i i G i g . ,Yew\ 1994. 72
(18). 24-34.
[lo] Transfermium Working GroupoflUPACand lUPAP([) H Wilkinson. A. H.
Wapstra. I . Ulehla. R. C. Barber. N. N. Greenwood. 4 Hrynkiewicz, Y. P.
Jcannin. M. Lefort, M. Sakai. Purr Appl. C%rni.1993. 6.5. 1757- 1814).
[I 11 D k BriicrrnirirR&r sc/\tcri E/e~lrnleiitc~
107, 1/18 rind I l N ( E d . : P. Armhruster).
Geaellschaft fur Schwertonenforschung, Darnistadt, 1993
[I21 IUPAC Commission on Nomenclature of Inorganic ('hemistry (A. M.
Siirgeson. Chair, Purr .4ppl. Chcrii. 1994. 66. 2419- 2421)
[I31 P. Armhruster. Nudrr. Cheni Tech Luh. 1995, 43(1). 53.
[14] D. C. Hoffman. personal communication. 1995.
1151 Quoted from M. Freemantle. C h m . En!: Netri 1995. Y ( I 9 ) ~7.
[i6] R. Smolancruk. A Sobicrewski. paper in [5a].
1171 P Moller. .I. R. Nix. W. D. Myers. W. J. Swiatecki. 4 1 . h r r r :Vur/. Dutu Trrhic
1995. SY. 1135-381.
Catalytic Asymmetric Carbonyl -Ene Reactions
David J. Berrisford* and Carsten Bolm*
As one of the fundamental bond-forming reactions, the carbony1 -ene reaction between an aldehyde and an alkene bearing
an allylic hydrogen attracts considerable attention"] from the
synthetic community. Given the versatile chemistry of the resulting hoinoallylic alcohols, both the intra- and intermolecular
versions of asymmetric carbonyl -ene reactions are valuable
processes.[" Within the field of catalysis[31the continuing improvements in the efficiency of chiral Lewis acids and the development of novcl ene chemistry occur in concert. We wish to
highlight a number of these developments.
I*]Dr. I).
.I. Hzrrt\lbrd
Dep'it titictit ( i t ('hemisrry
U n i r o r \ i t y 01 Manchester Institute of Science and Technology
1'0 t k i x 88. (il3-Manchestei M60 lQD (UK)
T e l e l a ~ In(.
code +(161) 236-7677
P I - O DI-.
~ c.. nl,iill
Pachhereich <'hcmie der Universitit Marhurg
0 - 3 5 0 3 1 Mat-hui-r (Germany)
A recent publication by Carreira et al.'41 documents further
advances i n this already topical area. The authors describe a
titanium-catalyzed asymmetric carbonyl -ene reaction of the
commodity chemical 2-methoxypropene ($49.30 L- '/Janssen)
with aldehydes (Scheme 1). When a catalyst prepared in situ
(R)-l (20mol%),
Ti(O/Pr), (10 mol%)
66-98% ee
from the tridentate ligand (Rj-1 and Ti(OiPr), in a 2:l ratio is
used, the yields and enantioselectivities of the new process are
generally high (Table 1). The most encouraging results, up to
98 YUre, are obtained with r,/J-ynals. Thus. this reaction offers
an alternative catalytic method for the synthesis of propargylic
alcohols. The reaction with benzaldehyde proceeds with only
modest selectivity, 66% ce, which is unusual for asymmetric
addition processes. The only %-branched aldehyde reported to
undergo addition, cyclohexanecarboxaldehyde, affords a
product with 75 YUee.
Table I . Yields and enantiomeric excesses o f the Ti-catalyzed asymmetric carbonyl- ene reaction [5] (see Scheme I )
Yield ["A] (81
Ph(CH,)3- C = C - C H O
Ph C d - C H O
ric variants using milder Lewis acids as catalysts have been
restricted to especially reactive aldehydes in intermolecular processes or to intramolecular reactions. For example. Yamamoto
et al. used the aluminum-based chiral Lewis acid (R)-2 in catalyzed asymmetric carbonyl-ene reactions (Scheme 3) .[81 However, the choice of enophile is limited to highly electron-deficient
aromatic aldehydes such as pentafluorobenzaldehyde and
chloral. Both simple 2,2-disubstituted alkenes and vinyl sulfides
undergo enantioselective reaction with a maximum c'e of 88 o/o
even with catalytic quantities (20 mol%) of the Lewis acid.
R = CSFs; 20 mol Yo (R)-2
R = C02Me; 0.5 mol% (RJ-3
88% yield, 88% ee
94% yield, 99% ee
\ \ o
The vinyl ethers obtained from asymmetric ene reactions are
valuable precursors for synthetically important optically active
compounds (Scheme 2). Acid hydrolysis affords the corresponding methyl ketones, thus providing an alternative to asymmetric methyl ketone aldol additions.[', 61 Oxidative cleavage of
the enol ethers with ozone affords the corresponding P-hydroxy
esters. and osmium-catalyzed dihydroxylation with N-morpholine-A'-oxide (NMO) gives ketodiols.
0 ~ 0 4 NMO
acetone, H 2 0
Scheme Z
(R)-3:X = H, Y = CI
(R)-4:X = Y = Br
Scheme 3
The asymmetric carbonyl -ene reaction has also been developed further by Mikami et al."b."l The reaction of glyoxylate
enophiles with the readily available Lewis acids [TiX2BtNOL][''
(X = CI, Br), for example ( R ) - 3 (Scheme 3). gives outstanding
enantioselectivities. Many of the earlier developments have been
thoroughly reviewed."] However, a number of important recent
advances are worth highlighting.[lo-'sl Extremely low catalyst
loadings (0.5 mol%)) can be used with vinyl sulfides and selenides in the glyoxylate-ene reaction.["] Changing the Lewis
acid to ( R ) - 4 enables certain trisubstituted alkenes to be used
with excellent enantio- and diastereocontrol.[' Vinyl ethers,
which are more reactive than their thioether counterparts, undergo ene reactions with high enantioselectivities when ( R ) - 3 is
employed as catalyst.["I Thus, addition of 2-phenoxybutene to
chloroacetaldehyde in the presence of 10 mol% of (R)-3 gives
the corresponding ene product in 53% yield with 9 7 % e~
(Scheme 4) .L'zl Under these Lewis acidic conditions phenoxy
[a] The corresponding 0-hydroxy ketones. which wei-eobtained by treatment ofthe
reaction mixture with E t 2 0 ; 2 h HCI. were isolated and analyzed.
Et2O I
chiral catalyst
molecular sieves
The recent work by Carreira et al. is an extension of earlier
studies"] in which a titanium(iv) catalyst prepared in situ from
the tridentate ligand (R)-1 and Ti(OiPr), was used to achieve
Mukaiyama aldol additions with high enantioselectivities. The
chiral ligand used in both the ene and aldol chemistry is prepared from 3-broino-5-tcrr-butylsaIicylaldehydeand '-amino2'-hydroxy-l,l '-binaphthol. This enantiomerically pure amino
alcohol is obtained from the convenient oxidative coupling procedure['] of Smri-ina et al. We expect further applications of this
valuable chiral biaryl ligand.
Usually intermolecular ene reactions of simple aldehydes with
otherwise inactivated 1 ,I -disubstituted alkenes require stoichiometric amounts of powerful Lewis acids."] Therefore, asymmetScIierne 4.
(R)-4 (10 mol %)
4A MS. 0°C.
84% yield, 94:6 s y n m t i ,
syn 89% ee
p ) - 3( 1 0 mol %)
48, MS, OOC.
nioicctilxr cievea.
53% yield, 97% ee
cthers are more stable than the corresponding hexyl and methyl
Owing to the impressive levels of stereocontrol achieved with
this method. a number of concise syntheses"] of important
bioactivc targets can be devised. Recent studies by the Mikami
group focus on two fragments of the immunosuppressant rapamycin" -31 and the prostacyclin analogue isocarbacylin; the latter
appli~;i!ion is notable for using a forinaldehyde-ene reaction." 'I
An enc mechanism is also implicated in the asymmetric "aldol"
additions of ketene silyl acetals of thioesters to aldehydes1151
of silyl enol cthers to glyoxylate esters (Scheme 5).[l6]The lack
of accompanying silyl transfer is in contrast to other asymmetric
Mukxiyuna-type aldol reactions." 'I
67% yield, 95:5 Z:f,
Z: >99% ee
Schenic C
The new methods developed by Carreira. Mikami, and others
widen the scope of asymmetric catalytic ene reactions. Studies
on new
often provide the necessary mechanistic
insights from which further developments in reaction protocol
ensue. With a high degree of confidence we can predict that
discoveries of even more practical chiral Lewis acid catalysts,
displaying wider substrate tolerance and requiring lower catalyst loadings, will continue apace.
Gel-man version. diiyew. C'hr1n. 1995, i07. 1862 - 1864
[I] a ) B. B. Snidcr in Cwnprrlii~ns~w
Or:,unii, . S > / i f h i m \ . I ol 2 (Eds.: B M Trost,
1. Fleming), Pergamon. Oxford, 1991, p. 527; ihid Lhi. 5 . p 1. h) K . Mikami.
M. Shimiru. C l i i ~ ~Rn..
1992. 97. 1011: c ) K M Terxia. S.
Nartsawa. T. Nakai. Sinlei/ 1992, 255: d) R M. Bor/illeri. S. M Weinreb,
$j~nthe\is 1995. 347.
[?] a) S. Sakane, K. Maruoka. H . Yamamoto. 7c/rahcr/ro/r L ? i t . 1985. 26. 5535;
b) rL'/ru/zi&o/r 1986, 40. 2203. c) K . Narasaka. Y Haqaslii. S. Shirnxia. Chrni.
L<,/t. 1988, 1609.
[3] a) K Maruoka. H. Yamamoto in Cu/rr/i(11 . A . ~ i ~ i ~ ~ i i .Si~w//ic,.\;.s
v i ~ m
I . Ojima). VCH. Weinheim, 1993, p. 413; b) R. Noyori. . 4 , \ \ / i i / i i i ~ f r i~i ~' u / t i / v . s ~ \
rii Orxunir Si~nt/ic~i.s,
Wiley. NeN York, 1994; c ) K . Niirasiiki. Si~ni/\
1991. 1.
141 E. Carreira. W, Lee, R. A. Singer. J. An?. Uiiw Soc. 1995. 117. 3649.
[5] E. Carreira. R. A. Singer, W. Lee, J. Am. Cliwii. Sot 1994. ii6. 8837.
[6] Catallred Mukaiyama-type aldol reactions of silyl e n d cthcrs or silyl kctene
acetals with aldehydes lead to the same products For reccnt advances see:
G. E. Keck. D Krishnainurthy. J. .4m.Chrwi. Soi.. 1995. 117. 2363. and references therein.
[7] a) M Smri.tna. M. Lorenc. V. Hanus. P. Sedmera. P. Koi.ov\k?. .I Or,y C ' h i .
1992. 57. 1917: h) M. Smri-ma. J. Polikova. S VyskoCil. P. Kotov\ky, ihid.
1993. SX. 4534.
[XI K . Maruokn. Y. Hoshino, T. Shirasaka. H. Yamamotu. / c ~ i ! - u / w / r mLi e / / . 1988.
79. 3967.
[9] The formulae in this article merely imply the stoichioinetric composition rather
t h a n the solution structure. For recent investigations o f t h e structures ofchiral
Ti complexes see: a) T. J. Boyle. N . W Eilerts. J. A. Heppert, F. Takusagawa.
1994. 13. 2218; b) E. J. Corey. M . A . 1 etavic. M . C. Noe, S.
Sarshar. Trirrrihrdwii L i d / / . 1994, 35. 7553. c ) K . V. Gothclf. R . G. H~irell,K . A
Jmgensen. J A m . CArm Soc. 1995, 117, 4435.
[lo] lV, Terada. S. Matsukahii. K.Mikami. J. Chim S o i ( ' l i w i ! . C'o~iiii?roi.1993.
[ l l ] a ) M . Terada. Y .Motoyama. K . Mtkami. 7 i ~ / r d i c ~ i / i ~Lt,ri.
~ ! i 1994, 35, 6693;
h) K . Mikami. Y. Motoyama. M.Terada. Iriorg C h i . 4crti 1994. 333. 71.
[12] We thank Professor Mikami, Tokyo Institute ofTechnoIogy. Ibr helpful discussions iind disclosure of unpublished material. a ) K . Mikaini, E. Saka, M .
Terada. unpuhlished results. b) E. Snwa. .Wasriv'\ Tiit,\/.\, Tokyo Inatitute 01'
Technology, 1992.
[I31 d ) K . Mikami. A Yoshtda. f i ~ i r a ~ i r t l r uLc,i/.
1994. 13. 77Y3: h) K. Mikami.
S. Narisawii. M . Shirnim. M . Terada. J. 4/12. C.//twi .SOL 1992. /i4. 6566,
[14] K. Mikami. A. Yoshida. Sj,ri/i>ft 1995. 29.
[15] K . Mikami, S . Matsukawa. .I A m C'hiwi. SOL 1994. / / h , 4077.
[16] a) K. Mikami, S. Matsukawa. J. A I J I .Chtwi. Soc. 1993. 115. 7039: h) 7e/rahrr/roii Lc//. 1994. 3.5, 3133.
[17] T. K. Hollis. B. Bosnich. .I .4ni C'hcm. S o . . 1995. /Iq. 4570
[18] For a new type ol'highly a c t t x titanium catalysts for ,ir)minetric glyoxylatc
etie reactions: a ) M . Terada. K Mikami. .L Chiwii. S oi. C h i . C I J I I I I H I ~ .
1994, 833, b) D. Kitamoto, H . Imma. T. Nakai. / i > / r d w / r o t i Lc//. 1995. 30.
Keywords: asymmetric syntheses . carbonyl -ene reactions .
catalysis chiral auxiliaries . titanium compounds
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