J. A m . Chem. SOC.1986, 108, 6405-6406 conformation is quadrangular [ 13631' I with the six bonds joining C(3) to C(29) forming a *convex side" and a pseudo mirror plane transfixing the double bond and the C(6) atom. The chloride ion is held within the molecule by hydrogen bonding with two N H and one O H groups. The positive charge resides on the pyrrolidinium nitrogen atom as attested by the longer than usual bond lengths (-1.522 %.)of the attached a-carbon atoms.Iz In summary, the structure of manzamine A hydrochloride is unprecedented in nature.I3 Moreover, its provenance is problematical as there appears to be no obvious biogenetic path. Acknowledgment. We thank Prof. K. L. Rinehart, Jr., University of Illinois, for recording the mass spectra. Supplementary Material Available: Tables of atomic coordinates, anisotropic displacement parameters, bond lengths, bond angles, and torsional angles (8 pages); table of structure factors (45 pages). Ordering information is given on any current masthead page.
6405
Scheme I [ A U ( C - H ~ X N C ) ~ ] ~ B F ,( 1 ) / 2 ( 1 m o l 2 ) RCHO
R~xcook R,,
,,COOMe
A
CNCH2COOMe ( 4 ) , CH,Cl,,
25 OC
0-N
0-N
trms-5
3a: PhCHO 3b : ( E )-n-PrCH=CHCHO 3c: (E)-MeCH=CMeCHO
cis-5
M : MeCHO C-NlbCH2CH2NRz
3e: 3 f : e-HexCHO i-PrCHO 39: t-BuCHO
Za: NR2 = N E t 2 &h2
Zb: NR2 = N k 2
Ph z
Scheme 11"
6
(12) Menabue, L.;Pellacani, G. C.; Albinati, A.; Ganazzoli, F.; Cariati, F.; Rassu, G. Inorg. Chem. Acta 1982, 58, 227-231. Barlein, F.; Mostad, A. Acta Chem. Scand., Ser. B 1981, 835, 613-619. ( 1 3) Christophersen, C. In The Alkaloids; Brossi, A., Ed.; Academic Press: New York, 1985;Vol. 4, pp 25-1 1 1 . Specialist Periodical Reports, The A/ka/oids;The Chemical Society: London, 1971-1983; Vol. 1-1 3.
\
7 OH
NH z
8
" ( a ) Concentrated HCI, M e O H , 50 O C , 3 h. (b) 6 N HCI, 80 O C , 6 h; amberlite IR-120B (H'). (c) LiAIH,/THF, reflux, 4 h; H20.
Catalytic Asymmetric Aldol Reaction: Reaction of Aldehydes with Isocyanoacetate Catalyzed by a Chiral Ferrocenylphosphine-Gold(1) Complex Yoshihiko Ito,* Masaya Sawamura, and Tamio Hayashi* Department of Synthetic Chemistry, Faculty of Engineering, Kyoto Iiniversity, Kyoto 606, Japan Received June 2, 1986 There has been great interest in the enantioselective aldol reactions of enolates with aldehydes to produce optically active P-hydroxycarbonyl compounds1 and considerable efforts have been devoted to developing effective chiral enolates, e.g., boron enolates of chiral ketonesZ and imides3 and tin enolates coordinated with chiral diamine^.^ Yet, there have been few reports on the use of chiral catalysts for such reaction^.^ Here we report that a chiral ferrocenylphosphine-gold(1) complex catalyzes the asymmetric aldol reaction of an isocyanoacetate with aldehydes,&* producing with high enoptically active 5-alkyl-2-oxazoline-4-carboxylates antio- and diastereoselectivity which are useful synthetic inter( I ) For reviews: (a) Heathcock, C. H. In Asymmetric Synthesis: Morrison, J. D., Ed.; Academic Press: New York, 1984;Vol. 3,p 11 1. (b) Evans, D. A.; Nelson, J. V.; Taber, T. R. Top. Stereochem. 1982, 13, 1. (2) Masamune, S.;Choy, W.; Kerdesky, F. A. J.; Imperiali, B. J. Am. Chem. SOC.1981, 103, 1566. (3) Evans, D. A.; Bartroli, J.; Shih, T. L. J. Am. Chem. SOC.1981, 103,
2127. (4) Iwasawa, N.; Mukaiyama, T. Chem. Lerr. 1982, 1441. (5) (a) Formation of optically active aldol-type product has been reported in the reaction of p-nitrobenzaidehyde with acetone catalyzed by Zn(I1) complexes of amino acid esters: Nakagawa, M.; Nakao, H.; Watanabe, K Chem. Lett. 1985, 391. (b) Asymmetric aldol reaction (90% ee) and high trans selectivity (>97%) were observed in the reaction of secondary and tertiary alkyl aldehydes 3e-g, while acetaldehyde (3d)gave the lower selectivity. The gold catalyst was also effective for the reaction of a,P-unsaturated aldehydes 3b and 3c to give the corresponding oxazolines of 87% ee and 95% ee, respectively. It appears that the aldehydes with the larger substitutent gave the higher enantio- and diastereoselectivity. The high efficiency of the ferrocenylphosphine ligand 2 may be visualized by the transition state A where the dialkylamino H
/p\
group at the end of the side chain on 2 participates in the formation of enolate of isocyanoacetate coordinated with gold." It is probable that the participation may permit a favorable arrangement of the enolate and aldehyde on the gold(1) at the diastereomeric transition state to bring about high stereoselectivity. Use of the phosphine ligand 9,'* which is analogous to 2a but with 3-(diethy1amino)propyl side chain, resulted in the formation of 5a with 26% ee, indicating that the distance between the amino group and the ferrocene moiety is of crucial importance for the selectivity. The ferrocenylphosphine BPPFA (10)" which lacks H.
p
2&(h2 PPh 2
9: X =
Supplementary Material Available: IH NMR data for the oxazolines 5 (1 page). Ordering information is given on any current masthead page. (21) (R)-2,2'-Bis(di-p-tolylphosphino)-l,l'-binaphthyl: Takaya, H.; Mashima, K.; Koyano, K.; Yagi, M.; Kumobayashi, H.; Taketomi, T.; Akutagawa, S . ; Noyori, R. J . Org. Chem. 1986, 51, 629. (22) Pearson, R. G . J . Chem. Ed. 1968, 45, 581 and 643. (23) The ?'Pand 'HNMR spectra of the ferrocenylphosphine 2 complexed with gold(]), silver(I), or copper(1) supported the mode of the coordination, which will be fully described elsewhere.
Unusual pKs and Bond Paths of 1,3-Dilithiocyclobutane
A
10: X =
gave almost racemic oxazolines. It should be noted that the use of gold is essential for the high selectivity, silver or copper catalyst being much less selective. This may be ascribed to the stronger affinity of gold(1) to phosphorus atoms.22 The ligand 2 can coordinate to gold with two phosphorus atoms leaving two nitrogen atoms free while silver or copper forms undesirable species by coordination of 2 with nitrogen atom(s) instead of p h o s p h o r ~ s . ~ ~
N&(CH2)3NEt2 NMe2
(BPPFA)
the side chain, as well as ~hiraphos,'~ DIOP,20and pTolBINAP?' (16) Satisfactory spectral and analytical data were obtained on all new compounds (see supplementary material). (17) It has been observed that the copper-catalyzed aldol reaction is accelerated by the addition of triethylamine.'a {,l8) [a]2'D -312O (c 0.69, chloroform). Prepared in a similar manner to 2b. (19) (S,S)-1,2-Bis(diphenylphosphino)butane: Fryzuk, M. D.; Bosnich, B. J . Am. Chem. Soc. 1977, 99, 6262. (20) (-)-2,3-OIsopropylidene-2,3-dihydroxy-1,4-bis(diphenylphmphino)butane: Kagan, H. B.; Dang, T. P. J . Am. Chem. SOC.1972, 94, 6429.
0002-7863/86/ 1508-6406$01.50/0
Steven M. Bachrach
Los Alamos National Laboratory Los Alamos. New Mexico 87545 Received April 4, 1986 The ion triplet model introduced by Streitwieserl interprets the stability of dianion salts in terms of the electrostatic interactions between the dianion and two bridging cations. The stability of the ion triplet is due to its four strong attractive interactions and only two weaker repulsive interactions. Streitwieser and Swanson2 experimentally determined the difference between the first and second pKs of 9,9'-bifluorenyl and 2,2'-biindenyl to be less than one pK unit. They concluded that the low second pK results from the formation of a stable ion triplet. The experimental3 and calculational4 work by Schleyer confirms the existence of the ion triplet. In fact, Schleyer, Kos, and Kaufmad have determined the disproportionation of 1,3-dilithiopropane to be 19.4 kcal mol-' endothermic a t the 3-21G level. This indicates that the second (1) Streitwieser, A,, Jr. Acc. Chem. Res. 1984, 17, 353. (2) Streitwieser, A,, Jr.; Swanson, J. T. J . Am. Chem. SOC.1983, 105, 2502. ( 3 ) Setzner, W. N.; Schleyer, P. v. R. Adu. Organomer. Chem. 1985, 24, 354. (4) Schleyer, P. v. R. Pure App. Chem. 1983, 55, 355. ( 5 ) Schleyer, P. v. R.; Kos, A. J.; Kaufman, E. J . Am. Chem. SOC.1983, 105, 7611.
0 1986 American Chemical Society
