close

Вход

Забыли?

вход по аккаунту

?

Enantioselective DielsЦAlder Approach to Angucyclinones from (S)-2-(p-Tolylsulfinyl)-1 4-naphthoquinone and Substituted Racemic Vinylcyclohexenes.

код для вставкиСкачать
COMMUNICATIONS
details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen(Germany), on quoting the depository number CSD-406176.
Received: December 12, 1996
Revised version: February 17, 1997 [Z9880IE]
German version: Angeii. Chem. 1997, 109, 1692- 1695
Keywords: cobalt . microporosity * phosphonate complexes
solid-state structures zeolite analogues
-
*
M. E. Davis. R. F. Loho, Chem. Muter. 1992, 4, 756; C. Y. Ortiz-Avila, C.
Bhardwaj. A . Cleartieid. fnorg. Cliem. 1994. 33, 2499: B. Z Wan, R. G . Anthony, G 2 Peng, A. Clearfield, J Catal. 1994, t U t , 19; J. L. Snover, M. E.
Thompson. J. 4ni. Chem. Soc. 1994, 116, 765; G. Alberti, M. Casciola, R.
Palombari, A. Peraio, SolidState Ionics 1992,58, 339; J. L. Colon, C. Y. Yang,
A. Clearfield. C . R Martin, J. P h j s . Chem. 1988, 92, 5777: G . Cao, H. Hang,
T. E. Mallouk. Arc. Chem. Res. 1992, 25, 420; D . Deniaud, B. Schollorn, D .
Mansuy. J. Rouxel. P. Battioni, B. Bujoli, Chem. Muter. 1995, 7,995.
K. Maeda, Y Kiyozumi, F. Mizukami, Angew. Chem. 1994, 106,2429, Angeir.
Cheni. lnf Ed Engl. 1994, 33, 2335; K. Maeda. J Akimoto, Y. Kiyozumi, F.
Mizukami. J C'heni. Sor Chem. Coninlun. 1995. 1033: K . Maedd, J. Akimoto,
Y Kiyommi. F. Mizukami. Angeiv. Chrm. 1995, 107, 1313: Angeiv. Cliem. Inr.
Ed Eng/ 1995. 34. 1199; J. L. Bideau. C Payen, P Palvadeau. B. Bujoli. fnorg.
Chmi 1994, 33. 4885.
J. Zubieta. Cnmmennr.~Inorg. Chem. 1994, 16, 153; A. Clearfield, ihid. 1990, 10.
89; H. Byrd. A . Clearfield, D . Poojary. K. P. Reis, M. E. Thompson, Cheni.
Muter. 1996.8.2239; P. Gendrdud, M E. de Roy, J. P. Besse, fnorg. Chum 1996,
35, 6108, K J. Martin. P J. Squattrito, A. Clearfield, Inorg. Chim. Arta 1989,
155. 7: L. J. Sxwrrs, V. J. Carter. A . R. Armstrong, P. G . Bruce, P. A. Wright,
B. E Gore. .I Chmi. Soc. Drrlron Trans. 1996, 31 59; A. Caheza, M. A. G . Ardnda. F. M. Canlero, D Lozano, M. Martinez-Lara, S. Bruque. J. Solid State
Cheni. 1996. 121. 181 ; D M. Poojary. D . Grohol. A. Clearfield, Angeit.. Chem.
1995. 1U7. 1650. Angew Chcm. fnr. Ed. Engl. 1995.34, 1508; D. M. Poojary, A.
C a b e m M A. G. Aranda. S. Bruque, A. Clearfield, fnorg. Chem. 1996, 35,
1468.
V. Soghomonian. R. Diaz. R. C. Haushalter, C. J. O'Connor, J. Zubietd, Inorg.
Chw~r.1995. 34. 4460.
D M. Poojary. B. Zhang, P. Bellinghausen, A Clearfield, Inurg. Chern. 1996,
35. 5254: D. M. Poojary, B. Zhang, P. Bellinghausen, A Clearfield, ihid. 1996,
3.5. 4942. V Soghomonian, Q. Chen, R. C. Haushalter, J. ZUbietd, Angew.
Ch~~tn.
1995. 107. 229: Angen. Chem. fnt. Ed. Engl. 1995, 34, 223; R LaDucd,
D. Rose. J. R. D. DeBord. R. Haushalter, C. J. OConnor, J. Zubietd. J Solid
Srrire C'licnf. 1996, 123, 408; G . Bonavia, R C. Haushalter, C J. O'Connor, J.
Zubieta, fno,x Clwm. 1996,35,5603; G . Alberti, U. Costantino. F. Marmottini,
R. Vivani. P Zappelli, Angex.. Chem. 1993, 105, 1396; Angeiv. Chem. Int Ed.
L+igI. 1993. 32. 1357.
S Drumel. P. Janvier, 8. Bujoli, J Chem. S o t . Chem. Commun. 1995, 1051
S. C. Sevor. Angew. Cheiii 1996, 108, 2814; Angeri, Chcm fnt. Ed. Engl. 1996,
35. 2630
Enantioselective Diels-Alder Approach to
Angucyclinones from (S)-2-(p-Tolylsulfinyl)1,4-naphthoquinone and Substituted Racemic
Vinylcyclohexenes**
M. Carmen Carreiio,* Antonio Urbano, and Jean Fischer
Angucyclines are a large group of naturally occurring
quinones of microbial origin"] that display a broad range of
biological activities.'*] This family of antibiotics shares a benz[a][*] Dr. M. C Carreiio, D r A. Urbano
[**I
Departamento de Quimica Orginica (C-I)
Universidad Autonoma
Cantohlanco, E-28049 Madrid (Spain)
Fax Int code +(1)397-3966
e-mail. carmen.carrenno@ruam.es
Prof J Fischer
Laboratoire de Cristdliochimle. UA 424
Universite Louis Pasteur, Strasbourg (France)
This work was supported by the Direccion General de Investigacion Cientifica
y Tecnica (grant no. PB95-0174)
A n g m . Chiw? Inr. E d EngI. 1997, 36, No. 15
C VCH
anthracene framework of decaketide origin,'31 ;is well as a
methyl group a t C3 and an oxygen functionality at C1. The
main structural differences among the members are found in the
aromatic or hydroaromatic nature of the A and/or B rings.
Some examples of angucyclinone antibiotics are ( +)-emycin A,
SF 2315A, and SF 2315B.
(+)-ernycioA
SF 231 5A
SF 23158
These challenging structures and their diverse biological activities have stimulated many synthetic studies of these comp o u n d ~ , [including
~]
several total syntheses.[51The most general
strategy employed for the regioselective construction of the angular tetracyclic core was the Diels-Alder reaction between a
substituted naphthoquinone and a vinylcyclohexene. Efficient
asymmetric syntheses were achieved by Sulikowski et a P d *
from appropriately functionalized chiral dienes obtained from
(-)-quinic acid, and by Larsen et aI.,["I who used a chiral catalyst in the cycloaddition step that allowed kinetic resolution of
the diene partner. To our knowledge no chiral dienophile has yet
been used in asymmetric angucyclinone syntheses.
We studied the dienophilic behavior of enantiomerically pure
sulfinyl quinones,L6]and found a high ability of the sulfoxide to
control the regiochemistry, endo selectivity, and rr-facial selectivity of cycloadditions with a wide range of dienes. We established the domino[7' Diels-Alder reaction/pyrolytic sulfoxide
elimination as a general one-pot strategy to enantiomerically
pure polycyclic dihydroquinones. This sequence could be applied to the synthesis of angucyclinones provided that substituted vinylcyclohexenes such as 2 (Scheme 1) reacted in a
diastereoselective manner. We here report the first enantioselective approach to angucyclinones in which the homochiral
sulfinyl quinone 1 is used to discriminate between both faces of
a racemic vinylcyclohexene with a bulky alkoxy substituent at
the allylic position.
A first test of this possibility was the ready reaction of (+)l[*]
with (+)-3-vinyl-2-cyclohexenol (2a;Ig1Scheme I ) . We isolated 3a (28%) and 4 (51%) by flash chromatography. The
stereochemistry of 3a, which resulted from spontaneous pyrolysis of the sulfoxide in the initially formed adduct, fulfilled the
expectations based on previous work with semicyclic di4 was derived from 3a in a frage n e ~ . [ ~ ~ . Anthraquinone
'.'~]
mentation process[4",
probably promoted by the free hydroxyl group and favored by the long reaction time required
(3 d). The enantiomeric excess and absolute configuration of 3a
could not be determined at this stage due to its facile transformation into 4 under the experimental conditions necessary for
preparing the corresponding Mosher esters." To avoid the
formation of 4 we thought of preparing a more stable derivative
of 3a en route to the angucyclinone functionality. Thus, treatment of 3a with m-chloro peroxybenzoic acid (m-CPBA) afforded epoxide 5a (90 Oh)by the exclusive attack of the oxidant from
the x face (cis to H12b).['21 The Mosher esters["] of 5a confirmed the absolute configurations shown In Scheme 1 for 3a
and 5a. Nevertheless, the observed ee of 50 %I for 5a[I3]reflected
low selectivity in the cycloaddition step.
The lability of 3a and the low diastereoselectivity obtained
with hydroxydiene 2a prompted us to check a bulkier alkoxy
substituent on the diene moiety to better differentiate the diene
Verlag.sjiesrllsc1ia~mbH. 0-69451 Weinhenn, 1997
5a3
~157I)-~833i97i36/5-162tS
17 .W+ 50.0
1621
COMMUNlCATlONS
Table 1. Selected physical and spectroscopic data for 3b, 3d,5b, Sd, 7b, and 7d.
[a]:' = +106.4 (c = 0 5 in CHCI,); ' H N M R (200MHz,
CDCI3):~=8.06(m,2H),7.67(m,2H),5.57(ddd,J=1.2,2.7,3.9Hz,1H),3.75
(ddd,J=3.9,5.2,9.2Hz,lH),3.37(dt,J=3.6,9.2H~,lH),3.41(ddt,J=1.9,
3b. M.P. 141-142°C;
24.5, 3.9 Hz, 1 H), 3.09 (dddd,J = 1.7,2.7, 5.2,24.5 Hz, 1 H), 2.4-1.3 (m, 6 H ) , 0.72
(S, 9 H ) , -0.12 ( s , 3H), -0.36 (s, 3H); I3C NMR ( S O MHz, CDCI,): 6 = 184.3,
183.9, 144.7, 141.1, 137.8, 133.2, 132.9, 132.8, 131.6, 126.4, 125.8, 115.1, 78.0,44.8,
36.9, 34 3, 26.1, 25.5 (3C), 25.2, 17 7, -4.9, -5.1.
(+)-5a-d
4:R=H
+
1
R'ouR2
6:R=Me
mCPBA
CH&
0 OC,4h
3d: M.p 189-190°C; [a];' = 3.5 (c = 0.5 in CHCI,); ' H N M R (200 MHz, CDCI,): 6 = 8.04 (m, 2H), 7.68 (m, 2H), 5.56 (t, J = 2.9 Hz, 1 H), 3.69 (ddd, J = 3.8,
5.1,9.5Hz, l H ) , 3 . 3 6 ( d t , J = 3 . 6 , 9.5Hz, l H ) , 3.40(ddt, J = 1 . 8 , 24.5, 3.9H2,
l H ) , 3.09 (dddd, J = l . S , 2.7, 4.3, 24.5Hz, l H ) , 2.30 (m, 1 H ) , 1.95 (m, l H ) ,
1.8-1.4(m,3H),1.00(d,J=5.7Hz,3H),0.72(s,9H),
-0.13(s,3H), -0.40(s,
3H); "C NMR (SOMHz, CDCI,): 6=184.3, 183.9, 144.9, 141.1, 137.1, 133.2,
133.1, 132.9, 131.7, 126.5, 125.9, 115.4, 77.1,45.6,44.4,42.7, 33.2, 25.8,25.5(3C),
21.8, 17.8, -4.9, -5.1.
5b: M.p. 235-236°C; [a]:'=
47.1 ( ~ ~ 0 in. 7CHCI,); ' H N M R (200MHz,
CDCI,): 6 = 8.05 (m, 2H), 7.68 (m, 2 H ) , 3 77 (dq, J = 9.9, 1.4 Hz, 1 H), 3.58 (dt,
J = 20.2, 1.9 Hz, 1 H), 2 79 (dt, J = 20.2, 1.6 Hz, 1 H), 3.47 (dt, J = 3.8, 9.9 Hz,
1 H), 3.24(q, J = 1.7 Hz. 1 H), 2.1 - 1.3 (m, 6 H ) , 0.65 (s, 9H), -0.11 (s, 3 H ) , -0.43
133.1,
( s , ~ H ) ;"CNMR(50MHz,CDC13):6=184.2, 183.1,144.7,137.9,133.4,
132.4, 131.6, 126.5, 126.0, 75.4, 61.5, 55.9, 44.5, 35.3, 32.6, 25.3 (3C), 24.6, 21.3,
17.6, -4.7, -5.3.
5d: M.p. 235-236T;[a]2 = +72 3 (c = 0 5 inCHCI,); 'HNMR(200 MHz, CDC1,):S = 8.04(m,2H), 7.67(m,2H),3.72(dq, J = l O . O , 1.4 Hz, 1 H),3.57and2.77
( 2 d t , J = 2 0 . 3 , 1 . 6 H ~ , 2 H ) , 3 5 0 ( d t ,J = 3 . 7 , !O.OHz, l H ) , 3.23(q, J = 1 . 6 H z ,
l H ) , 1.94(m, 1 H), 1 8 - 1 . 3 ( m , 4 H ) , l . O 4 ( d , J = 5.9Hz, 3H),0.65(s,9H), -0.11
( s . ~ H ) -O.~S(S,~H);'~CNMR(~OMH~,CDCI,):~
.
=184.3,183.1,144.8,137.9,
133.4, 133.1. 132.5. 131.7, 126.6, 126.0, 74.7, 61.0, 56.0,44.1,43.9,41.1, 28.4,25.4
(3C), 24 6, 21.7, 17.6, -4.6, -5 2.
7b: M.p 111-112°C; [%I;' = - 62.9 (c = 0.5 in CHCI,); ' H N M R (200MH2,
CDCI,): 6 = 8.21 (m, 2H), 8.20 (d, J = 8.1 Hz. l H ) , 7.74 (m, 2 H ) , 7.47 (d,
J=8.1Hz,1H),6.36(dd,J=3.0,35Hz,1H),3-06(m,1H),2.84(ddd,J=6.3,
10.2,17.2Hz,1H),2.3-2.0(m,2H),1.85-1.65(m,2H),0.81(~,9H),0.31
(s,3H),
0.03 (s, 3H); ',C N M R (SO MHz, CDCI,): 6 =185.4, 183.5, 145.9, 141.3, 135.4,
135.0, 133.9, 133.4, 133.2, 132.5, 131.2, 127.3, 126.5, 126.3, 63.2, 31.8, 30.7, 26.0,
18.3, 15.9, -4.3, -5.0.
7d: M p. 125-126°C; [a]:' = - 59.0 ( c = 0.1 in CHCI,); ' H N M R (200 MHz,
CDCI,): 6 = 8.20 (m, 2 H ) , 8.19 (d, J =7.9 Hz, 1 H), 7.74 (m, 2H), 7.46 (d,
J=7.9H~,lH),6.37(t,J=5.9Hz,IH),2.86(dd,J=10.8,15.5Hz,1H),274
(dd, J = 5.1, 15 5 Hz, 1H),2.19 (ddt, J=1.5,13.3, 5.9Hz, 1 H), 2.0-1.8 (m, 1 H),
1.56 (ddd, J = 6.2, 8.7, 13.3 Hz, 1 H), 1.18 (d, J = 6.6 Hz, 3H), 0.77 (s, 9H), 0.17
( s , ~ H ) -0.04(~,3H);'~CNMR(50MHz,CDCI,):6=185.9,183.4,148.1,142.8
,
135.4, 133.9, 133.6, 133.3, 133.2, 132.7, 131.8, 127.3, 126.5, 126.5, 66.3, 40.8, 39.0,
26.9, 26.0, 23.1, 18.1, -4.2, -4.5.
+
b: R' = TBS;
0
R2 = H
c: R' = H; R2 = M e (cis)
d: R' = TBS; R2 = M e (cis)
(+)-I
0
(+)-3a-d(J1,72b= 9-10 H Z )
I
p
j.
R'O
(-)-2a-b
(-)-7b:R = H
(-)-7d:R = M e
Scheme 1. DBU = 1,8-diazabicyclo[5.4.O]undec-7-ene;TBS = tert-butyldimethylsilyl; R T = room temperature.
faces.[g1The Diels-Alder reaction of (+)-I with (+)-1-terfbutyldimethylsilyloxy-3-vinylcyclohex-2-ene(2b)19' afforded 3b
(75 YO)as the exclusive reaction product (Table 1) together with
unchanged diene. After flash chromatography we could recover
40 O
h of optically active (-)-2b ([a];' = - 38, c = 1 in CHCI,),
showing that kinetic resolution had occurred during the cycloaddition. The ee value of greater than 97 YOfor 3b1I4]indicated excellent diastereoselectivity for the Diels-Alder reaction between (+)-1 and 2b. The m-CPBA epoxidation of 3b again gave
the sole epoxide 5b (90 %). In contrast, desilylation of recovered
(-)-2b with TBAF afforded diene (-)-2a ([a];' = - 47, c = 1
in CHCI,) whose Mosher esters showed an ee value of 50% and
( S ) configuration at C1 (Scheme 1).
To extend these positive results and open an easy access to the
substituted A ring of several angucyclinones, we investigated the
behavior of dienes cis-2c and cis-2d with a methyl group at C5.
Cycloaddition of (+)-1 with (~)-5-methyl-3-vinylcyclohex-2enol ( 2 ~ ) ~afforded
"~
3c (26%) and 6 (SO0/,) after flash chromatography. The m-CPBA oxidation of 3c gave epoxide 5c
(82 YO)whose Mosher esters'"] again showed the absolute configuration depicted in Scheme 1 and 50 % diastereoselectivity
On the other hand, (i-)-1-tertfor the initial cy~loaddition."~]
butyldimethylsilyloxy-5-methyl-3-vinylcyclohex-2-ene(Zd), ob~'
chloride (TBSCI), imtained from 2 ~ ' ' (tert-butyldimethylsilyl
idazole, N,N-dimethylformamide (DMF), 87 %), reacted with
(+)-1 to yield exclusively 3d (73 O/O), whose epoxidation afforded 5d (86 %, ee > 97 "/.) .[I4] This high enantiomeric excess indicated total stereocontrol in both the Diels-Alder reaction and
epoxidation. Moreover, the absolute configuration of 5d was
confirmed by X-ray
Enantiomerically pure epoxides 5b and 5d could be useful synthetic intermediates for the
1622
0 VCH P2rlagsgeseIlschaft mbH, 0-69451
Weinherm, 1997
synthesis of antibiotics SF 2315A and SF 2315B that are lacking
a hydroxy group at the C8 position.
The approach to the anthraquinonic skeleton of (-)emycin A required the aromatization of B ring of 3b and 3d
without affecting the stereogenic moiety. Therefore, treatment
of 3b or 3d with 1,8-diazabicyclo[5.4.O]undec-7-ene(DBU) in
CH,Cl, at room temperature"'] afforded anthraquinones 7b
(62%, ee>97%)[14] and 7d (58%, ee>97%),"41 respectively.
According to the model proposed for (S)-p-tolylsulfinylquinone cycloadditions[6b-dland the known behavior of
dienes such as 2,15',f,101
the absolute configuration of the new
stereogenic centers should result from the matched endo approach of (R)-2 from the face containing the less sterically demanding pseudoaxial substituent at the allylic position and towards the face of the quinone with the lone electron pair at
sulfur in the s-trans conformation of 1 (Scheme 1).
We have reported the first asymmetric approach to the tetracyclic skeleton of angucyclinones from a chiral dienophile. The
sulfinyl group on the quinonic framework promoted a double
induction in Diels-Alder cycloadditions leading to efficient kinetic resolution of (+)-2. Further studies on the latter process
and total syntheses of angucyclinones are in progress.
Received: January 30, 1997 [Z l0052IE]
German version: Angtw. Chem. 1997, 109, 1695-1697
0570-0833/97/361S-1622S 17.50 + SOjO
Angew Chem. Int Ed. Engl. 1997, 36, No 15
COMMUNICATIONS
-
Keywords: angucyclinones antibiotics
. cycloadditions quinones
-
- asymmetric synthesis
[I] a) R. H Thomson, Naturally Occurring QuinonesIV, 4thed., Blackie, London, 1996; b) J. Rohr, R. Thiericke, Nat. Prod. Rep. 1992, 9. 103-137.
[2] a) S. Kondo. S. Gomi, D. Ikeda, M. Hamada, T. Takeuchi, H Iwai, J. Seki, H.
Hoshino. J Antihiof. 1991, 44, 1228-1236; b) M. Ogasawara. M. Hasegawa,
Y. Hamagishi. H. Kamei, T Oki, ihid. 1992, 45, 129-132.
[3] S. J. Gou1d.X C Cheng,C. Melville,J Am. Chem. SOC.1994, 116, 1800-1804,
and references therein.
[4] Recent work: a ) K. Kim. J Reibenspies, G. Sulikowski, J Org. Cliem. 1992,
57. 5557 - 5559. b) K. Krohn. F. Ballwanz, W. Baltus, Liebig.$ Ann Chem.
: c ) K Krohn.K.Khanbabaee,ibid. 1994,1109-1112;d) F. L.
. Larsen, Tetrahedron Lett. 1994, 35,8693-8696; e) K. Krohn,
W. Dr6ge. F. Hintze, Ann. Quin7. 1995, 91, 388-393; f) V. A. Boyd. J. Reibenspies, G. A. Sulikowski, Tetrahedron Lett. 1995,36,4001-4004, g ) K. Kim, Y
Guo. G A. Sulikowski. J Org. Chem. 1995,60, 6866-6871; h) D. S. Larsen,
M. D. O'Shea. ihid. 1996, 61, 5681 -5683.
[S] Recent work a ) D. S. Larsen, M. D. O'Shea, Tetrahedron Lett. 1993, 34,
1373 1376: b) K. Krohn, K. Khanbabaee, Angew. Chem. 1994, 106, 100102: 4 i I p l ' . (%em. Int. Ed Engl. 1994, 33, 99-100; c) D. S. Larsen, M D.
O'Shed. J C h ~ mSoc Perkin T,.ans. 1 1995, 1019-1028; d) K. Kim, G. A.
Sulikowski. A n p i < . Chem. 1995. 107, 2587-2589: Angew Chem. I n [ . Ed. Engl.
1995. 34, 2396-2398; e) V. A. Boyd. G. A. Sulikowski, J A m Chem. SOC.
1995, 117, 8472 8473. f) D. S. Larsen, M. D. O'Shea. S. Brooker, Chem.
Commun. 1996. 203-204; g) G. Matsuo, Y. Miki, M. Nakata, S. Matsumura,
K. Toshima, h i d . 1996. 225-226.
Overview of o u r work: a) M C. Carreiio, Chem. Rev. 1995, 95, 1717-1760;
recent work. b) M. C. Carreiio, J. L. Garcia Ruano, M. A. Toledo. A. Urbano,
V. Stefani. C. L . Remor, J Fischer, J Org. Chem. 1996,61,503-509;~) M. C.
Carrefto. J. L. Garcia Ruano, A. Urbano, M. A. Hoyos, ihid 1996, 61. 29802985: d ) M. C. Carreiio, J. L. Garcia Ruano, A. Urbano. M. I. Lopez-Solera,
ihid. 1997. 62. 976-981.
a ) L. F.Tietze. U. Beifuss, Angel%.Chem. 1993, f05,137-170; AngeM. Chem.
Int. Ed. EngI. 1993. 32. 131-163; b) L. F. Tietze, Chem. Reit 1996, 96, 115136.
M C Carrefto. J. L Garcia Ruano, A. Urbano, Sjnthesis 1992, 651653.
L. Strekowski. S. Kong, M. A. Battiste, J Org Chem. 1988, 53, 901 -904.
a) M J. Fisher. W. J. Hehre, S. D. Kahn, L. E. Overman, J Am. Chem. Soc.
1988, 110. 4625-4633, b) S. C. Ddtta, R. W. Franck. R. Triphaty, G. J.
Quigley, L. Huang, S. Chen. A. Sihaed, ibid. 1990, 112, 8472-8478.
J. A. Dale. H. S. Mosher, J Am. Chem. SOC.1973, 95, 512-519.
The relative configuration was established by comparison with a similar intermediate prepared by Sulikowski [Sd] in the total synthesis of SF 2315A.
When the cycloaddition was carried out in water the reaction was faster (completed in 12 h at room temperature) but with a lower enantiomeric excess
(2036 )
The enantiomeric excesses were evaluated by ' H N M R spectroscopy using
c h i d lanthanide shift reagents: [Eu(tfc),] for 3b and 5d, and [Yb(hfc),] for 7b
and 7d. The required racemic compounds were obtained from racemic quinone
I [81
S. J. Hecker. C. H. Heathcock, J Org. Chem. 1985, 50, 5159-5166.
The absolute structure was determined by comparing refinements of both configurations, and confirmed by refining Flacks x parameter (G. Bernardinelli,
H. D. Flack. Acto Crystallogr. Sect. A 1987.43,75-78). Crystallographicdata
(excluding structure factors) for (+)-5d have been deposited with the Cambridge Crystallographic Data Centre as suplementary publication no. CCDC100 117. Copiesofthedatacan beobtained freeofchargeon application toThe
Director, CCDC. 12 Union Road, Cambridge CB2 IEZ, UK (fax: int. code
+ ( I 223) 336-033: e-mail deposit@chemcrys.cam.ac.uk).
These results contradict those reported by Sulikowski et a]. [4g]. who described
no reaction for a similar system with DBU in benzene at O'C
Evidence for a Stepwise Addition of Carbenes
to Strained Double Bonds: Reactions of
Dihalocarbenes with Cyclopropenes""
Jurgen Weber and Udo H. Brinker*
Dedicated to Professor William von Eggers Doering
on the occasion of his 80th birthday
The most thoroughly investigated pathway of carbene stabilization is addition to carbon-carbon double bonds. Early studies by Skell and Woodworth['] consider the singlet carbene addition a one-step process in which two new bonds are formed
simultaneously. Even though the addition of singlet carbenes is
concerted, it cannot be synchronous according to orbital symmetry considerations.[2] Jones et al.13] suggested that the concept of nucleophilicity and electrophilicity, as applied to intermolecular additions of carbenes to alkenes, can be interpreted as
the different contributions of the highest occupied and lowest
unoccupied molecular orbitals (HOMOSand LUMOs). For instance, during the electrophilic attack of a dihalocarbene,
charge is transferred from the olefin's HOMO to the empty p
orbital of the carbene (LUMO). Calculations of activated complexesL4]for addition of dihalocarbenes to simple olefins support this direction of charge transfer. These calculations also
show a shorter distance from the carbene carbon to one of the
carbon atoms of the double bond.
Although addition of photochemically generated monohalocarbenes to 1,2-dimethylcyclobutene was postulated to proceed
via z~itterions,*'~
no conclusive evidence of their intermediacyC61 was p r 0 ~ i d e d . lWe
~ ~ present here evidence that charge
transfer during reactions of dihalocarbenes with differently substituted cyclopropenes leads to polarization of the activated
complex or even to an intermediate dipolar species with complete charge separation.
Only few dihalocarbene reactions with cyclopropenes are
known.[" With the exception of perfluoro-l,3-dimethylbicyclo[l .I.O]b~tane,[~]
geminal dihalobicyclobutanes, the addition
products of dihalocarbenes, have never been isolated or unambiguously identified by spectroscopy. Instead cyclobutenes,
probably formed by cationic cyclopropylallyl (CCA) rearrangements,["] were found as the only products.
We initially reported that, for the first time, 2,3-diaryl-l,l-dihalo-l,3-butadienes were formed along with 1,3-diaryl-2,3-dihalocyclo-I -butenes by the reactions of dihalocarbenes (: CF, ,
:CCI, , :CBr, , :CFC1, :CFBr) with 1,2-diarylcyclopropenes
(Scheme l).['ll We now present evidence for a step-wise addition of dihalocarbenes to strained double bonds of cyclopropenes. For the mechanistic studies of the formation of butadienes
and cyclobutenes, three different aryl substituents were utilized.
In the reactions of 1,2-diphenyIcyclopropene(1) with dichlorocarbene, the ratios of the products, that is, of butadienes 2[lr1to
cyclobutenes 5,[lZ1were nearly independent of the method of
carbene generation (Table
This indicates that the same
[*I Prof. U . H. Brinker
Institut fur Organische Chemie der Universitat
Wahringer Strasse 38, A-1090 Wien (Austria)
Fax: Int. code (1)31367-2240
e-mail: udo.brinker@ univie.ac.at
Dr. J. Weber
Department of Chemistry, State University of New York at Binghamton
(USA)
[**I Carbene Rearrangements, Part 47 Prof. W. M. Jones (University of Florida)
and Dr. L. X u are gratefully acknowledged for helpful discussions. Part 46:
J. Weher, U. H. Brinker, Tetrahedron 1996, 52, 14641.
Angex. Chon Int E d EngI. 1997, 36, No. I5
8 VCH
Verlagsgesellschaft mbH. 0-69451 Wemhetm, 1997
0570-0S33~97;36/5-1623S 17.50t .WJO
1623
Документ
Категория
Без категории
Просмотров
2
Размер файла
422 Кб
Теги
racemic, dielsцalder, approach, vinylcyclohexene, enantioselectivity, naphthoquinone, angucyclinone, substituted, tolylsulfinyl
1/--страниц
Пожаловаться на содержимое документа