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Highly Enantioselective Homoaldol Additions with Chiral N-AllylureasЧApplication to the Synthesis of Optically Pure -Lactones.

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[XI 9 was synthesized from phenyl- I-seleno-8-o-glucoside by transacetalization with benzaldehyde dimethyl acetal and subsequent acetylation. The
' H - N M R coupling constants of the protons on the pyran ring of 9 are
J1.2=10.10, J2., 8.50, and J,,4=J4s=9.35 Hz.
[Y] For the significance of analogous radical-stabilizing effects see: P. S.
Skell, K . J. Shea in J. Kochi: Free Radical,$. Vol. 2, Wiley, New York
1973: D. H. R. Barton, W. Hartwig, W. B. Motherwell, J . Chem. SOC.
Chem. Commun. 1982. 447.
H3C-N
a
NH
M
H3c
4
0
Highly Enantioselective Homoaldol Additions with
Chiral N-Allylureas- Application to the Synthesis
of Optically Pure y-Lactones""
By Hanno Roder, Giinter Helmchen*, Eva-Maria Peters,
Karl Peters, and Hans-Georg von Schnering
Dedicated to Projessor Ulrich Schmidt on the occasion
of his 60th birthday
In favorable cases, the reaction of aldehydes and ketones with hetero-substituted allylmetal compounds 2 proceeds with high regio- and diastereoselectivity
(X = OCONiPr,l'"l, X = NR-CO-NR;"']).
Since the products can be hydrolyzed to aldehydes, which react to lactols
3, compounds 2 function as synthetic equivalents of homoenolates 1. Oxidation of the lactols affords lactones,
many of which are important pheromones, terpenes, or
chiral synthetic building blocks which are accessible via
the "homoaldol reaction" in only one CC coupling step.
1
2
3
We have now developed the first enantioselective homoaldol reaction involving a chiral allyl system of type
212.31.
For this purpose we use as a novel reagent for asymmetric synthesis the cyclic urea derivative 4, accessible in
one step by fusing (-)-ephedrinium chloride with ureaI4l
[55-65%, m.p.= 177--179"C, [ a ] g -44.5 (c=3, methanol)]. Using standard methods, one obtains from 4 the Nallyl derivative 5 [92%, m.p. =68-69S°C, [a]g +22.7
(c = 3, methanol)]. 5 can be smoothly deprotonated with nbutyllithium to the allyllithium compound 6a and transmetalated['"I to 6b ( - 2 0 T , red-orange solution) with
chlorotris(diethylamino)titaniumlsl. Reaction of the titanium compound 6b with the aldehydes 7a-c as well as,
surprisingly, with the methyl ketone 7d leads highly stereoselectively to the homoaldol adducts 8a-d. These adducts have, as expected, a cis-configurated double bond1'S6l
and can be obtained diastereomerically pure by recrystallization['] (Table 1). The pure enamides 8a, b, d are methanolyzed analogously to that described in [lb] to the O-methyllactols 9 a , b, d ; the reagent 4 can be re-isolated in 9598% yield by extraction. The crude compounds 9 can be
directly oxidized with m-chloroperbenzoic acid (MCPBA)
to the y-lactones 10a, b, d (Table 2) using the method de[*I Prof. Dr. G. Helmchen, DipLChem. H. Roder
Institut fur Organische Chemie der Universitat
Am Hubland, D-8700 Wurzburg (FRO)
Prof. Dr. H. G. von Schnering, E.-M. Peters, Dr. K. Peters
Max-Planck-lnstitut fur Festkorperforschung
Heisenbergstrasse I,D-7000 Stuttgart 80 (FRG)
[**I This work was supported by the Fonds der Chemischen Industrie.
898
0 Verlag Chemie GmbH, 0-6940 Weinheim, 1984
8a-8d
6a, M = L i
6b. M = (NEt,),Ti
10a, b, d
9a, b, d
7-10: a, R' = nOct, R2 = JI; b, R1 = Et, R2 = H
c, R' = iPr, R2 = H; d , R' = iPr, R2 = M e
Table I . Reaction of the allyltitanium compound 6b with the carbonyl compounds R 1 R 2 C 0 , 7a-d, to give the homoaldol adducts 8a-d (THF,
-20°C).
Homoaldol
adduct [a]
Yield
[%I [b]
Diaslereosel.
[c]
Yield
[Yo] [d]
Diastereomeric
ratio [d]
8a
8b
8c
8d
96
94
9s
93
94
96
96
98
:6
:4
61
63
2200 : 1
>zoo : 1
:4
:2
81
-
150 : 1
[a] Predominant homoaldol adduct. All compounds were characterized by
C H N analyses (+0.3"/11)as well as hy 'H-NMR (400 MHz) and mass spectra.
[b] Relative to 5 . [c] Diastereoselecxivity was determined for 8a, b by HPLC
and for 8 a , c, d by 'H-NMR (400 MHz). [d] After recrystallization from nhexane or n-hexane/ethyl acetate.
scribed by Grieco et a1.Ix1.The configuration of 10a and
lob, whose enantiomers are the pheromones of various
species of beetles"], as well as that of 10d were determined
by comparison of the optical rotations with reliable literature data (Table 2). The configuration of the reagent 4 is
Table 2. Methanolysis of the homoaldol adducts 8a, b, d to the O-methyllactols 9a, b, d and their Grieco oxidation [XI to the optically active y-lactones
IOa, b, d.
y-Lactone
[a1
Yield
["hl [bl
[all,
Absol.
config.
1Oa
10b
1Od
99
79
97
[a]2d'-41.1 [c] (c=5, CH,OH)
[~l]??:'-53.7 [d] (c= 1, CH3OH)
[a]?;-10.5 ( ~ = 3 CH3OH)
,
[a]?? - 10.9 [el ( c = I,CHCI,)
S
S
R [el
[a] Purified by liquid chromatography and kugelrohr distilled. [b] Yield relative to the diastereomerically pure homoaldol adducts 8a, b, d . [c] Rotation
of natural (R)-IOa: [a]$ f 4 1 . 1 ( c = 5 , CH,OH); G. T. Muys, B. van der Ven,
A. P. Dejonge, Appl. Microhiol. I / (1963) 389. [d] Rotation of (R)-lOb prepared from L-glutamic acid: [a]:;' +53.2 ( c = l , CH,OH): for (S)-lob:
[a]?? -53.2 ( c = 1, CH,OH); U. Ravid, R. M. Silverstein, L. R. Smith, Tetrahedron 34 (1978) 1449. [el The ahsolute configuration was determined by
crystal structure analysis of 8c (Fig. I). Rotation of (R)-lOd prepared from
(R)-linalool (92.4% ee): [a]:: - 10.2 (c= 1.07, CHCI,); K. Mori, T. Ebata,
S. Takechi, Tetrahedron 40 (1984) 1761.
0570-0833/84/1111-0898 $ 02.50/0
A n y e w . Chem. Int. Ed. Engl. 23 (1984) No. 11
established by a crystal structure analysis of the enamide
8d (Fig. 1).
,Fig. I. Stereoscopic projection of the structure of 8d in the crystal. Further
details of the crystal structure investigation can be obtained from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2, by quoting the depository number CSD 50966, the names of
the authors and the journal citation.
For rationalization of configurative correlational relationships of the homoaldol addition, we assume that the
reaction proceeds via a chair-like transition state in which
the larger substituent at the carbonyl group preferentially
adopts the equatorial
The homoaldol additions described d o not depend on
the concentration of the reactants and, because of the
ready accessibility and re-isolability of the reagent 4, can
be performed on a large scale. Both enantiomers of 4 are
available. Because of the high stereoselectivity of the reaction and the possibility of subsequent purification by crystallization, the products can be obtained enantiomerically
pure.
General Procedure
8 : n-Butyllithium (0.1 1 mol, ca. 2~ in hexane) is added to 30 mL tetrahydrofuran (THF) (under an inert gas atmosphere at -78°C) and the mixture stirred. A solution of 5 (0.1 mol) in 75 mL T H F is added dropwise to this mixture, and after 25 min a solution of chlorotris(diethy1amino)titanium (0. I 1
mol) in 30 mL T H F is also added dropwise. The mixture is warmed u p to
-20°C and 45 min later a solution of 7 (0.10 mol) in 10 mL T H F is injected
in. After ca. 2 h, water is added and the mixture is taken up in ether and extracted with 10% NaHSO, and with water. The enamides 8 obtained from
the ether solution after drying and concentrating are chemically largely pure
(see Table I).
[4] This reaction has already been performed with (+)-ephedrine, but on
the basis of mechanistic considetdtions, the product was incorrectly assigned the trans-configuration: W. J. Close, J. Org. Chem. I5 (1950)
1131.
[5] M. T. Reetz, R. Urz, T. Schuster, Synthesis 1983, 540.
[6] a) H. Ahlbrecht, Chimia 31 (1977) 391 ; b) A. N. Tischler, M. H. Tischler,
Tetrahedron Lett. 1978, 3407.
[7] An allylmagnesium compound prepared from 6a by transmetalation
with MgBr2' EtzO exhibits high y-regioselectivity but no stereoselectivitY.
[S] P. A. Grieco, T. Oguri, Y. Yokohama, Tetrahedron Lett. 1978. 419.
[9] a) J. W. Wheeler, G. M. Happ, J. Araujo, J. M. Pasteels, Tetrahedron
Letf. 1972, 4635; b) R. M. Silverstein, J. C. Young, ACS Symp. Srr. 23
(1976) 1.
[lo] The change in the notation for the absolute configuration in the series
88-d and 10a, b, d (cf. Table 2) is determined by the alteration in the
substituent priorities.
A Binuclear, Mixed-Valence Mov"v-Complex;
The Crystal Structure of I(C9H21N3)2M02V'051(Br3)2
By Karl WieghardP, Gabriele Backes-Dahmann,
Willy Herrmann. and Johannes Weiss
Binuclear, 0x0-bridged complexes of molybdenum(v1IV)have been discussed as active centers in the enzymes nitrate-reductase, sulfite-oxidase, and xanthine-oxidase['].
ESR spectra of the active forms of these enzymes indicate
an O,N,S-coordinated MoV center, thus suggesting that
mixed-valence complexes of the type MoV/Mo'" or MeV'/
Mo" could be present. For the former type there is only
one well characterized example[21;we report here on the
characterization of the first mixed-valence MoV'/MoV
complex.
Oxidation of LMo(CO)~"' with semiconcentrated nitric
acid furnishes the yellow, diamagnetic cation
[L2M02v10s]2' 1 , where L is the facially coordinated
N,N',N"-trimethyl-l,4,7-triazacyclononane
ligand. Salts of
1 with (Br3)0, PFF and ClO," have been isolated in the
crystalline statel4I.
According to the X-ray structure analysis of 1 (Br3)2151
a
binuclear, ~ ~ - o x o - b r i d g ecation
d
with two pseudooctahedrally coordinated molybdenum(v1) centers is present (Fig.
Received: July 23, 1984 [ Z 933 IE]
German version: Angew. Chem. 96 (1984) 895
CAS Registry numbers:
4, 92841-65-1 ; 5, 92720-98-4; 6a, 92720-96-2; 6b, 92720-97-3; 7a, 124-19-6;
7b, 123-38-6; 7e, 78-84-2; 'Id, 563-80-4; 8a, 92720-99-5; 8b, 92721-00-1; Sc,
92721-01-2; 8d, 92721-02-3; 9a, 92721-03-4; 9b, 74577-87-0; 9d, 92721-04-5;
10a, 69830-92-8; lob, 41035-07-8; 10d, 92721-05-6; CH2=CHCH2CI, 107-05I; (Et2N)3TiCI,6607-37-0.
[ I ] a) D. Hoppe, F. Lichtenberg, Angew. Chem. 96 (1984) 241; Angew.
Chem. Int. Ed. Engl. 23 (1984) 239 and literature cited therein (since
1979); b) T. Hassel, D. Seebach, ibid. 91 (1979) 427; 18 (1979) 399.
[2] The alkylation of some chiral reagents of the type 2 has already been
studied: a) H. Ahlbrecht, G. Bonnet, D. Enders, G. Zimmermann, Tetrahedron Lett. 21 (1980) 3175; b) T. Mukaiyama, H. Hayashi, T. Miwa, K.
Narasaka, Chem. Lett. 1982. 1637.
[ 3 ] Related chiral d'-synthons (dllylsilanes and allylboranes): a) T. Hayashi,
M. Konishi, M. Kumada, J . Org. Chem. 48 (1983) 281, and literature
cited therein; b) H. C . Brown, P. K. Jadhav, Tefrahedron Left. 25 (1984)
1215; and literature cited therein: c) R. W. Hoffmann, Angew. Chem. 94
(1982) 569; Angew. Chem. I n f . Ed. Engl. 21 (1982) 555; d) R. W. Hoffmann, B. Landmann, ibid. 96 (1984) 427; 23 (1984) 437; e) P. G. M.
Wuts, S. S. Bigelow, J . Chem. Sor. Chem. Commun. 1984, 736.
Anyew. Chem. Int. Ed. Engl. 23 (1984) No. 11
[A]
Fig. 1. Structure of 1 in the crystal of 1 (Br3)Z;selected bond lengths
and
angles ["I. Mo-Ol 1.694(7), Mo-02 1.696(7), Mo-03 1.898(1), Mo-NI
2.325(8), Mo-N2 2.355(8), Mo-N3 2.290(9); 0 I-Mo-02 104.7(4), 02-Mo-03
103.6(2), 01-Mo-03 104.4(3), NI-Mo-03 90.0(2), Nl-Mo-N2 73.2(3), N2Mo-N3 74.2(3), NI-Mo-N3 74.3(3), Mo-03-Mo' 180.0.
[*] Prof. Dr. K. Wieghardt, DipLChem. G. Backes-Dahmann,
Dipl.-Chem. W. Herrmann
Lehrstuhl fur Anorganische Chemie I der Universitat
Postfach 102148, D-4630 Bochum I (FRG)
Prof. Dr. J. Weiss
Anorganisch-chemisches lnstitut der Universitat
Im Neuenheimer Feld 270, D-6900 Heidelberg (FRG)
0 Verlag Chemie GmbH. 0-6940 Weinheirn, 1984
0570-0833/84/1 I 11-0899 $ 02.50/0
899
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chiral, allylureasчapplication, synthesis, optically, lactones, additional, homoaldol, enantioselectivity, pure, highly
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