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Bis(2 4 6-tri-tert-butylphenyl)stannanediyl A DiaryIstannylene without Donor Stabilization.

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exchanger (Dowcx 50 WX?. acid form). and subsequently eluted wilh 0.5 M aqueous
NH,. The resulting product mixture was separated by chromatography on S-Sepharose and o n Fractogcl TSK HW-40 (monitored with iodine. Rydon Smith. and
z-naphthol!sulfuric acid staining. and by UV detection at 210 nm). Total yield of I
and 2 was 0.9 g and 1.5 g. respectively.
Hexaacelyl dcrivativr of 1: Compound I (10 mg) was dissolved in anhydrous pyridine (3 mL) and acetic anhydride (1 mL). The solution was maintained at rooin
temperature for 15 h. Ice was then added. and the rcaction was extracted with
CHCI,. After chromatographic purification o n silicn gel wilh CHCI,,'CH,OH
( 9 9 : l ) . 5 mg of hexaacct~l-1was isolated. HR-El MS: iri;: 506.1865 (0.2%).
[:M + H i . calcd 506.1874 for C , , H , 2 N 0 , , ] . 446.1437 ( 3 % ) . [.U- AcNH,. calcd
446.14251, 330.1193 (4?0). Ihf - OCH,CH(OAc)CH,OAc. calcd 330.1188].
359.0662 (100%). ['CH,CH(OAc)CH,OAc. ber. 159.06571. 343.0584 (40%).
[AcOCH=CHNHAc' : her. 143.05821: ' H NMR (CDCI,. 270 MHL): d = 5.15.
5.10 ( 2 t. 9 Hz. 32-H. 4/j-H). 5.0 (d. 3.5 Hz. l x - H ) . 4.1 - 4 . 4 (m. 7 H ) . 3 . 6 5 (m.
OCH,). 2.0-2.1 (6 OAc)
Salhostatiii 2: [XI;; = I15 ( 1 , = 1. H,O): C,,H,,NO, (-721). CI M S : ni;: 322
( 1 0 0 " ; b ) . [ M + H ' ] . 3 0 4 ( 1 1 % ~ , [ . l . I H ' -H,0].286(YU'").[.UH'
- 2 H , O ] . 164
( 3 3 % ) . ['H,NC,H,,O,]:
' H NMR ([D,]DMS0,D20. 400MHr: see Table I ) .
"C NMR ([DJDMSO, 68 M H z ) : d = 52.8 (d. C-1'). 57.6 (d. C-2). 61.4 (I.C-6.
C-7'). 69 1 (I.C-1). 70.2. 70.5. 70.9. 72.9. 76.6. 81.7 ( 6 d. C-3. C-4. C-5. C-4'. C-5'.
C-6'). 120.4 (d. C-2'). 140.5 Is. C - 3 ' ) .
+
Bis(2,4,6-tri-tert-butylphenyl)stannanediyl: A
Diarylstannylene without Donor Stabilization**
Manfred Weidenbruch,* Josephin Schlaefke,
Annemarie Schafer, Karl Peters, Hans Georg
von Schnering. and Heinrich Marsmann
The nature of the tin-tin bonding in distannenes (distannaethenes) has not yet been completely rationalized. Thus, the
distannene 1 of Lappert et al. is the sole structurally characterized compound of this type, and in the solid state is best described as a double donor-acceptor adduct of two stannylenes
(stannanediyls) 2 (Scheme 1). Evidence for this includes the tin tin interatomic distance.". 21 which IS hardly shorter than that of
tin-tin single bonds,'31 the results of quantum mechanical calculations.[', 41 ' "Sn solid-state N M R data.[51and the dissociation of 1 in solution into two stannylene molecules 2.C6l
Heptaacctyl derivative or 2: salbostatin (50 mg) was dissolved i n anhydrous pyridine ( 3 mL) and acetic anhydride (1 mL). The solution was mainlained at room
temperature for 15 h. treated with ice, and extracted with CHCI,. Chromatographic
purification o n silica gel with CHCI,.CH,OH (99: I ) afforded 16.6 mg heptaacelyl
salbostatin 2'. HR-El MS: n i ' ; 615.2108 (4%). [ M ' ; calcd 615.2164 for
C,,H,,NO,,]. 555.1911 ( 2 5 % ) . [ M - AcOH. cakd 555.19521, 495.1698 (17Sbl.
[ M - 2AcOH. calcd 495.1741). 471.1743 (22"h). [M - AcOCH=CHOAc. calcd
471.17401, 231.0865 (100%). [AcOCH,CH,CH(OAc)CH(OAc)t. cakd 231 .OXhX]:
' H NMR (CDC13.400 M H r ) see Table 1. NO€ difference spectroscopy and Fig. 1.
Received. April 22. 1994 [Z68691E]
German bersion: Angiw . C'hiwi. 1994. 1116. 1936
[I] S . Urnelawn. K. Tsuchiya. H Umezawii. J. Anrihmf. 1970. 23. 20-27. H.
Zihner. H. Drautz. W. Weher i n Biuai~riwMicruhiul Prurliicrs: Scwi-i./i ofid
Di.si.owrx (Ed.: J. D. Bu'Lock. L. J. Nisbet. D. J. Winstanley). Academic Press.
New York. 1982. pp. 51 70. S. Breiding-Mack. A. Zeeck. J. Anrihiu/. 19117.40.
952 -960.
121 Y . Miyazaki. M . Shihuya. H. Sugawara. 0 . Kawaguchi. C Hirose. J. Nagatsu.
S. Esumi. J. A n r h i o / 1974. 27. 814-821: J. W. Westley. J. F. Blount. R. H.
Evans. C:M. Liu. ihid. 1977. 30. 610 612.
[3] E. F. Paulus. L. Vkrtesy, G. M. Sheldrick. Acru C r ~ . w d / u ~.%,<I.
r . C 1984. 40.
700 703.
[4] a ) J . A. F. Op den Kamp. P. P. M. Bonsen. L. L. M. Van Deenen. Biodiini.
B;up/l,n. .AC.IU 1969. 176. 298 305. E. Altmann. J. R. Brisson. M. B. Perry.
C o r h o h d . Rr.v. 1988. 1x3. 321 -331: h ) N. C. Phillips. L Chedid. J. M.
f.
6 , 678 -691
Bernard. M. Level. P Lrfrancier. J. B i d Rcaupunw U ~ d / 1987.
[5] L. Vertesy. H -W. Fehlhaber. A. Schulz (Hoechst AG). DE-A 3X36675Al.
19811: [CIiiwi. Ah\/,.. 19119. 113. 96134 XI.
(61 a ) H. Paulsen. F. R . Hciker. A~rgiw.('horn. 1980. Y2. 930-931. A n g r ~C / i m
h i t . Ed. En,q/. 1980. 19. 904-905: h) H. G. Fletcher. Jr.. J A m C h i w . Sol,.
1947. 69. 706-707.
(71 Y Shiga. H. Mizuno. H. Akanuma. J Bucleriol. 1993. 17.5, 7138-41.
[XI a) Y. Kcmada. S. Horii. J. Chcm SJC.
Cliiw. Commuu. 1972. 746-747: b) E
Truscheit. W Frommer. B. lunge. D. D. Schmidt, W. Wingender. A i r g e ~
Chpiif 1981. Y3. 738-155; .4/1gt'l\.ChPiTI Inr. Ed. E I I ~ I1981.
.
3.744 761.
[Y] Dr. F, E Beyhl (Hoechst AG). unpublished.
[lo] S. Ogawa. C. Uchida. Y.Yuming. J. Chrni. S i x . Chon. ( ' r i r n n i i m . 1992. 886
888.
[ l l ] S. Mufiio. EP-A O566275Al. 1992.
[12] M. J. McBride. J. C Ensign. J Bucrtvwl. 19W. 172.3631- 3643:C. Marino. M.
Curto. R. Bruno. M T. Rinaldo. l n t . J. B ~ o c h m i .1989. 21. 1369 1375.
1131 L. Vkrtesy. P. Schindler. H. Kogler. H. W. Fehlhaher (Hoechst AG). EP-A
.
1989. 1111. P193414Jl
0288897. 1988: [ C / ~ c n i.4h.\tr.
R,SnSnR,
2R,Sn:
2
1
R'
Sl:
/ \
RlSn-SnR:
3
Scheme 1 R
=
(Me,Si),CH. R '
RlSn:
+ R:Sn=SnR:
4
5
= 2.4.6-rPr,C,HZ.
Different behavior is observed for the tetraaryldistannene
N M R data,[7-81
retains its structural integrity even in solution. Moreover, trapping reactions
with c h a l ~ o g e n or
s ~phenylacetylene[81
~~
indicate the likely presence of a double bond in 5.The distannene 5 is formed together
with the stannylene 4 upon photolysis or thermolysis of the
cyclotristannane 3. with which it exists in thermal equilibrium
over a wide temperature range.") In the solid-state. however.
only the three-membered ring 3 is present at room temperature;[") hence no X-ray structure analysis on 5 has been possible.
The replacement of the 2.4,6-triisopropylphenyl groups R 1 in
4 and 5 with the significantly bulkier 2.4,6-tri-rerf-butylphenyl
groups R', in order to suppress the formation of the analogous
cyclotristannane, proved not possible at first. This was due not
only to the arylialkyl isomerization (R' + R3) previously
known for R' groups." '. ' I but also to disproportionation reactions of the presumed tin(n) intermediate species. Thus, reaction of the Grignard reagent 6 with tin(r1) chloride-which in the
case of the corresponding 2,4.6-triisopropylphenyl compound
had led smoothly to 3[8.y1--gave rise to a dark red solution.
from which, upon addition of sulfur. the tin sesquisulfide 7 with
rearranged alkyl groups was isolated. as well as tin(iv) cornpounds.
5.171which. according to "'Sn
[*I Prof. Dr. M. Wcidenbruch. Dip1 -Chem. J. Schlaefke. Dr. A. Schlfer
Fachbereich Chemie der Uiiiversitit
Car~-~on-Os5ietzky-Strdsse
9 - 11. D-2hi 11 Oldenburg ( F R G )
Telet'a'ar: Int. code + (441)798-3329
Dr. K. Peters, Prof. Dr. H. G . von Schnering.
Max-Planck-Institut f i r Festkijrperforschunc Stuttgart (FRG)
Prof. Dr. H. Marsrnann
Fachbereich Chemie der Universifil-GusamthochschulePaderborn ( F R G )
["I
Compounds of Germanium and Tin. Par1 13. This work was supported by the
Deutache Forschungsgemeinschaft and by the Fonds der Chemischen Industrie. Part 13: M. Weidenhruch. A. Ritschl. K . Peters. H. G. von Schnering. J
Or,quiromiv C ' h i w i . 1992. 437. C25
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R3
I S
I
Success was finally achieved by the reaction of the tin(n)
aniide 8[13' with 2,4.6-tri-rert-butylphenylIithi~m,[~~~
from
which highly air-sensitive, dark red crystals of 9 were obtained.
The 'H and I3C N M R spectra clearly show that insertion of the
unsaturated tin atom into one of the methyl C-H bonds of the
or//7o-/cr./-butyl substituents had not occurred. Furthermore,
molecular mass determinations (cryoscopic in benzene) and the
absence of tJ(11"Sn,117Sn)
coupling in the ""Sn N M R spectrum indicate the presence of monomeric stannylene molecules
in solution.
Sn[N(SiMqh]2
8
+
2R2Li
-
:S&
+
2LiN(SiMe3)2
9
A crqstal structure analysis"'] (Fig. 1) established the composition of 9 and confirmed that this stannylene also exists in
monomeric form in the crystal, since the shortest tin-tin distance (884 pm) lies outside of any bonding interaction. Whereas
C15
interaction between the C-H bond and the unsaturated tin
atom.
Compound 9 is the first diarylstannylene which exists without
intramolecular donor-stabilization."hl The only other structurally characterized diarylstannylene [2,4,6-(CF,),C,H2],Sn:
(10) probably owes its stability to the close contact between the
fluorine atoms of the ortho-CF, groups and the low-valent tin
atom.["J A recent report describes R'R4Sn: (11, R4 = 2.4.6[(Me,Si),CH],C,H,), whose substituents show similar steric demands to 9.["] Isolation of l l has not yet been accomplished.
Evidently, the bulky ortlio-/err-butyl groups in 9 not only
hinder cyclotristannane formation, but also destabilize a possible distannene. The ""Sn N M R spectrum of 9 is unusual and
shows, instead of the expected singlet. two signals at b = 961
and 1105 in an intensity ratio of about 4: 1 at room temperature.
These coalesce upon heating to 50.C into a single signal at
6 = 980, which persists even after cooling. The obvious supposition is that a partial isomerization of 9 into the sterically less
encumbered stanylene R2R3Sn: (12) takes place in solution: this
is supported not only by the 13C N M R spectrum, in which a
CH, group at 6 = 62.5 is detected unambiguously, but also
through trapping reactions, from which thus far only products
with one aryl/alkyl isomerized R3 group were isolable.
The positions of both signals is of interest since they are
clearly distinct from that of molecule Z*rsl as well as that of a
structurally related compound in which both C-H hydrogen
atoms of 2 are replaced with an ethylene bridge,['"] and that of
11,[181 which display drastically deshielded tin nuclei
(6 > 2200). Rather, the chemical shifts observed for 9 and 12 lie
in the region typical for hetero-substituted stannylenes,['O1 for
example S,r2'l and also for
Whereas these stannylenes
minimize their electron deficiency through interaction between
free electron pairs and an unoccupied 5prr-orbital at the tin
center, the reason for the similar shielding of the tin nuclei in 9
and 12 is currently still obscure.
E.xperinimtal Procedure.
0
I
A solution of2,4.6-tri-rerr-butylphenyllithium(14.7 g. 46 mmol) in toluene (70 mL)
was added slowly dropwise. with the exclusion of air and moi\turr. t o a solution 0 1
8 (10.0 g. 23 mmol) in toluene (40 mL). and the dark red mixture stirred for about
3 h. After concentration of the solution to 80 mL, cooling to -30 C afforded 9
(9.0g. 64%) as dark red rectangular crystals. M.p. 125 130 C . ' H N M R
(300MHz. C,D,,). 6 =1.16. 1.26. 1.33. 1.34. 1.38 (each s, 9 H ) . 1.6X (s. 6 H ) . 7.41
(s. 1 H). 7.44(a. 1 H). 7.46(s. 1 H). 7.57. 7.516; "C:'H) NMR (75.44 MHz.C,,D,):
6 = 31.54, 31.64, 31.77. 31.86, 32.Y0.33.23. 34.75. 3.5.09. 35.14. 38.80.40.09, 62.50,
11Y.68, 120.02. 122.20. 125.65, 128.87, 129.28, 148.13. 150.34. 150.47. 150.93.
156.70: ""Sn{'H/ N M R (112.22 MHz. [D,]toluene. Me&): 6 = Y50.6. 1120.1
(270 K): 960.8. 1105.0 (293 K ) , 980.4(323 K); UV:VIS (n-penlane):in,,,,
= 476 nin.
W
CIS
C32
Fig. I . Molcculiir Structure o f 9 in crystal (without H atoms). Selected bond lengths
[pm] :ind angles [ ] Sn C1 275.5(4). Sn-C7 226.7(4): Cl-Sn-C7 103.6(1). C K 2 C13 127.7(41. CI-Ch-C21 124.2(4). C7-CX-CZ5 123.9(4). C7-C12-C33 122.7(3).
the tin -carbon interatomic distances correspond to those in
Z,['I the C-Sn-C angle is widened by about 8". presumably on
account ofthe greater steric demands of the R 2 groups. The two
phenyl rings are each twisted by 54" from the C l-Sn-C7 plane.
forming an angle of 30" with respect to one another, thereby
permitting optimal orientation for the bulky orfho-tert-butyl
groups. Agostic interactions between the tin atom and the
neighboring methyl C - H bonds were not observed, since all
four or/l~o-trr.t-butylgroups point away from the tin atom. The
carbon atom C24 does approach the tin atom at a distance of
312 pm. though this distance is still probably too great for an
Received: April 6. 1994
Revised version: June 4. 1Y94 [Z68261E]
German verqion: A n z w . C / ~ w i1994.
.
106, 1938
[I]D. E. Goldberg. D. H. Harris. M . F. Lnppert. K . M . Thomas. .I C/iiwi. Sot,.
Chern. Conimim. 1976. 261.
[2] D. E. Goldberg. P. B. Hitchcock. M . F. Lappert, K . M . Thomaa. A. 1.Thorne.
T. Fjeldberg. A. Haaland, B. E. R. Schilling. J. C ' h m r . Soc. Dolion Em.\. 1986.
2387.
[?I A . Haaland, A. Hainrnel, H. Thomassen. H V. Volden. H. 8 . Singh. P. K
Khanna. Z . Nurirrfor.rch. B 1990. 45. 1143.
[4] a ) G Trinquier, J.-P. Malrieu. J. Aru. < ' h i . So(.. 1987. IOY. 5303: b) A. Snvin.
A. D. Becker. J. Had. R. Nesper. H. Preuss. H . G. von Schnering. Aiig<,iir
Cliern. 1991. 103. 421: A n g i w . < % c i i i . I n ! . Ed. EngI. 1991. 30. 409 c) H. Jacohsen, T. Ziegler, J. h i . CIiivn. S o . 1994. 116. 3667. and references therein.
[5] K . W. Zilm. G. A. Lawleas. R . M. Merrill. 1 M . Millar. C; G. Webb. J. An!.
Cliizrii. So<. 1987. 109, 7236.
[6] P. J. Davidson, D H . Harris, M . F. Lappert. J. Chrni. Soc. Dolrori T,.ori.\. 1976.
2228; T. Fjeldherg. A. Haaland. M. F. Lappert. B. E. R. Schilling. R. Seip. A . J.
Thorne. J. C%c'ni. Sor. Chr'iri. Commrm. 1982. 1407.
(71 S. Masamune. L. R. Sita. 1 A m . Cliuir. So<. 1985. 107. 63Y0.
~
COMMUNICATIONS
[XI M. Weidenbruch. A. Schafer. H.
C/IOli
KiIi:iii.
S. Pohl. \V. Saak. H. Marsinann.
Bw. 19Y2. 175. 563.
[Y] A . Schafcr. M . Weidenbruch. W. S u k . S. Pohl. H. Marsmaun. Aiigeii. C'/iwii
1991. 103. 873. 978: ,4ilgPIr'. C'/i?ni. /n/. E d €n,q/. 1991. 30. 834. 962.
[ l o ] F. J. Brady. C J. C'irdiii, D. J. Cardin. M. A . Convcry. M . M. Devereux. G A
Lau,less. J O r x o i i o i i i r / . Ciicvii 1991. 42/. 199.
[I I ] M . Weidenhruch. K . Schdl'trs. S Pohl. W Saak. K . Peters. H. G . von Schnering. J. O r g i i i i o i i i i ~ t C / i i w i . IY88. 346, 171.
(121 J. Prey. D. A Nugiel. Z. Rappoport. J Ovg. C/iwi. 1991. 56. 466.
[13] M . J. S Glane. D H. Harris, M. F. Lappert, P. P. Power. P. Riviire. M . Riviere-B,tudct. J C ' l i t w i . SO(..
DNIIOIZPuiis. IY77, 1004.
(141 M. Weidenhruch. K.Krmier. J Or,qoiioiiicr. Chcw 1985. 3YI. 159.
[I51 X-ray crystal structure analysis o f 9 : C,,,H,,Sn. h ,= 609.57. orthorhoinhie.
space group P k n . ii = 1767.3(4). h = 19 ?(4). I ' = 205Y.6(5) pm. 1' =
6971(3)x 1OhpmJ. L = X. pillLd
=1.161 g c
'. Mo,, radiation, graphite
monochroinator. 20,,,, = 55 . Wyckoff-scan. X730 independent reflectionr.
5738 observed independenr reflections ( F 3 n ( F ) ) .<:parameter r;itio = 17.2.
Solution by direct methods and refineineiit with t h e Siemens-SHELXTL-Plus
progmm sqstem. R = 0.050. R, = 0.046. Further derailsofthccrystal structure
investlaation may he obtained from the Fachinforinatioiis~entrumKarlsruhc.
D-76344 Eggenstein-Lropoldsli~ifen ( F R G ) . upon quoting the depository
numher CSD-400727.
[I61 The existence of(impure) 9 was presumed on the bask of ils Mdssbaucr spectrum: M. P. Biguood. P. J. Corvan. 1. J. Zuckernian. J. A m . C/imi, So<.. 1981.
103. 7643.
[17] H GI-Gt~macher.H. Pritzkow, E T. Edelmann. Oi~[ii7"1~i[,"'//ic.r,
1991. ill. 2 3
A second crystalline form of 10 with a weak tin- tin interaction is described: U
Lay. H . Pritzkou. H. Grutzmacher. J. C/icw. Soc. C'heni. Corwiiuri. 1992. 260.
1181 Y . Tokitoh. M. Saito. R. Okazaki. J A m . C/iciii. Soc. 1993. ll.5. 2065.
1191 M. Kira. R. Yauchihara. R. Hirano. C Kahuto. H. Sakurai. J. A i i i C/iwi. So(
1991. 113. 77x5.
[2l)] M. Veith, 0 . Recktcnwald. Top Curr. C h i . 1982. 104. 1.
[21] B. Wmcknieycr, J ,Mri,qii. Rer. 1985. 61. 536.
I n the presence of an aldehyde and a metal catalyst, cyclic
ketones are oxidized to lactones with molecular oxygen.'" '1 We
chose 2-phenylcyclohexanone ( I a) as the model compound for
our investigations into the asymmetric oxidation reaction, because 1 a is converted into lactone 2 a in high yields and with
good regioselectivities in the reaction catalyzed by achiral nickel
and copper complexes.[sl The enantiomeric excesses (cc) ob-
rac-1
a: n = 1, R = Ph
b: n = 1, R = 4-CI-Ph
c: n = 1. R = 4-MeO-Ph
d: n = O , R = P h
cat.* = Ni or Cu complex with chiral ligands
tained for lactone 2 a and ketone 1 a can be determined reliably
and unambiguously by HPLC on a chiral column. With the
optically active nickel(r1) complex 3a. rac-1 a was converted to
r.uc-2a, regardless of the reaction conditions employed; with the
corresponding copper complex. 2a was obtained with enantioselectivities of up to 69 o/o re.
3a: M = Ni, R = Alkyl, X = H
b: M = C U ,R = ~ B uX, = NO2
C: M = Cu, R = tBu, X = H
d: M = Cu, R =iPr, X = NO2
e: M = Cu. R = iPr, X = H
C a r s t e n Bolm,* G u n t h e r Schlingloff, and
Konrad Weickhardt
[*I
Prof. Dr. C. Bolm ['I. DipLChem. G. Schlingloff['], Dr. K . Weickhardt
lnstitut fur Organische Chemic der Uniwrsitlt
St. Johanns-Ring 19, CH-41)SO Basel (Swirzerland)
[ ' 1 New address. Fachbereich Chemie dcr Universitiit
Hans-Meerweiii-Straase. D-35032 Marhurg ( F R G )
Telefax: Int. code + (6421)28-8917
[**I This research w n s supported by thc SchNeirerischer Nationalfonds and the
Deutsche For~chun_psgemeiiisch~i~t
(project: oxygen transfer peroxide chemistry) We thank Profecsora Pfaltz and Schiess. Uni\,ersitiit Basel. for samples.
(SJ-1
e: n = 2 , R = P h
Optically Active Lactones from a
Baeyer -Villiger-Type Metal-Catalyzed
Oxidation with Molecular Oxygen**
Catalyzed asymmetric oxidations are of paramount importance for the synthesis ofchiral building blocks. Enantioselectivities of over 90 YOhave been achieved in the dihydroxylation of
olefins"] and in the epoxidation of ally1 alcohols'2J and nonfunctionalized cis a l k e n e ~ . ' ~In
] general. highly oxidized
reagents. such as peracids or other peroxy compounds, are employed as the source of oxygen. M u k n i j w m et al. reported that
molecular oxygen could also be used as a simple oxidizing agent
in the asymmetric oxidation of oletins provided that an oxygen
acceptor. such as an aldehyde. were present in stoichiometric
quantities.141As part of our investigations into the activation
and transfer of oxygen.[51we have now developed an enantioselective, metal-catalyzed variant of the Baeyer-Villiger oxidation. a reaction which had previously only been achieved with
the help of enzymes."]
(RJ-2
In order to achieve good reactivity and high asymmetric induction, several reaction parameters had to be optimized. The
best results were obtained with p-nitro-substituted copper complex 3b in water-saturated benzene and with pivalaldehyde as
the oxygen acceptor ( = coreducing agent) (Table 1). Use of
1 mol O/O of (S,S)-3b as catalyst at room temperature and under
an oxygen atmosphere resulted in formation of lactone (R)-2a
in 41 % yield and 65 O/O cc after 16 hours; at 6 -C. an increase in
Table I . Enantioselccti\,e Baeyer Villiger oxidation of cyclic ketones with (S.S)3 h.
Entry
Aldehyde
Ketone
rBuCHO
rBuCHO
iii-CI-PhCHO
p-MeO-PhCHO
{BuCHO
C,H, , C H O
fBuCH0
rBuCH0
rBuCHO
la
la
Ia
Lactone
Yield ['%I
ec'
41
41
32
65
69
49
1a
la
la
-
lh
43
53
21
lc
Id
65
61
["%I
[a]
59
61
ca 60 [el
65
47
[a] Determined by HPLC o n a chiral phase. [b] 6 d at 6 C. [c] Reaction time 5 d. [dl
The absolute configuration was not determined. [el N o base-line separation.
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