Highly enantioselective addition of (S)-lithiomethyl 1-naphthyl sulfoxide to ketones

Tcmhcdnm L.ettm. Vo131. No.37, pi 5349-5352 1990

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HIGHLYENANTIOSELECTIVE ADDITION OF (S)-LITHIOMETHYL l-NAPHTHYLSULFOXIDETO KETONES Hldetake

Department University,

of Industrial

SAKURABA*

Chemistry,

and Shigeru

USHIKI

Faculty of Engineering,

4834, Kanazawa-Mutsuura,

Yokohama,

Kanagawa

Kanto Gakuin

236, Japan

Summry: The anion of (Sj-(-)-methyl l-naphthyl sulfmide reacts enantioselectively alkyl phenyl ketones to give (SsSc!-B-hydrmysulfoxides with diastereaneric excess up to 100 %. Optically pure IS)-tertiary alcohols are prepared by desulfurizaticm the corresponding diastereomers.

Chiral Especially,

sulfoxides

have been widely

the asymmetric

reduction

used as a chiral auxiliary

of R-ketosulfoxides

sulfoxide was achieved

in a highly diastereoselectivity species with zinc cation. 293 However, the nucleophilic sulfinylcarbanion In contrast towards

with the reaction

compounds

exemplified

Solladie

et al.7 reported

the substituents

addition

proceeded

increased

selective

in 60 and 18% enantioselectivities,

sulfoxide -1 to aromatic ketones, of optically pure tertiary alcohols.

The general procedure

process. 536

for the addition

(scheme 1).

addition

However,

no enantioketones.

of the anion of (Sl-l-l-

and the successful

pure sulfoxide

to benzaldehyde, and 1-naphthyl

out with aromatic

of the lithium carbanion

Optically

sulfoxide

to p-pyridyl

respectively.

was carried

In this paper, we report a highly enantioselective

ketones -2 was as follows

of the sulfinylcarbanion

group from p-tolyl

methyl I-naphthyl preparation

of the chiral a-p-tolyl-

that the addition of (RI-lithiomethyl

addition of 1-naphthylsulfinylcarbanion

p-tolyl

by the chelated

with a low enantioselectivity.4

above, the addition

of methylsulfinyl

synthesis.'

derived from (RI-(+)-methyl to be controlled

the C=N bond of imines was a highly enantioselective

on changing groups,

to various carbonyl

for asymnetric

with (de) of

1 8-1o -

application

to the

of 1 to various (0138 g, 2 tmnol) in

Raney-Ni

R!..C/R2 H3C '

'OH

11

21 Raney-Ni

H3C &

115) [=lr

R
-459.8'

(c 0.1, EtOHl

Scheme

1

5349

11 tetrahydrofuran(THF, 5 ml) was added dropwise to a solution of lithium diethylamide (ca. 2.5 mnol) in THF (10 ml) at 0°C under nitrogen. To the cooled solution was added 2 (2.1 mmol) directly at -4O"C, and the reaction mixture was stirred at -40°C for 2 h.

The

reaction was quenched with saturated aqueous ammonium chloride (50 ml). The organic layer was separated off and the aqueous layer was extracted with dichloromethane. The combined organic layers were washed with brine, dried, and evaporated in vacua to give the diastereomericmixtures 2 and 4 of 8-hydroxysulfoxidesin 96-98% chemical yields. The total yields of the diastereomersand the diastereomericratios were determined by HPLC analysis on a silica gel (Zorbax SIL, 4.6 x 250 mm) using CH2C12-AcOEt (98:2) as a eluent.

Table 1. Enantioselective Addition of (S)-Lithiomethyl 1-Naphthyl Sulfoxide to Ketonesa) Ketone 2

R1COR2

b) B-Iiydroxysulfoxide 3(SsSc): Q(SsRc) (% de) ')

R1

R*

Ph

Me

100 :

0

(100)

Ph

Et

100 :

0

(100)

Pr

100 :

0

Ph

Bu

100 :

Ph

Pri

Ph

Bui

76 : 24

( 52)

Ph

But

75 : 25

( 50)

Ph

Hexyl

80 : 20

( 60)

Et

Me

53 : 47

(

Ph

Tertiary Alcohol 5c) B ee [aly /" (c l.O,solvent)(Config.)

-16.1 (EtOH)

loo(s)e)

(100)

-6.6 (acetone)

100(S)e)

0

(100)

-10.2 (acetone)

loo(s)e)

72 : 28

( 44)

6)

a) The reaction was carried out in a THF solution at -4O'C for 2 h. b) In 96-98% yields. c) In 80-85% yields. d) Determined by HPLC. Chem., 2, 1193(1982). e) C. R. Johnson and C. J. Stark, Jr., J. org. As shown in Table 1;the presence of a I-naphthyl substituent instead of a p-toly14'7 on a chiral sulfoxide group increased drastically the asymmetric induction for the nucleophilicaddition of the a-sulfinylcarbaniontowards aromatic ketones. The perfect enantiofacialselectivitywas achieved when the sulfinylcarbanionreacted with the ketone RCOC6H5 having linear alkyl substituents,R, such as methyl through n-butyl groups. However, there is a trend of decreasing stereoselectivitywith increasing size of the alkyl substituentof -2. The stereoselectivitydropped from 100 to 50% de in going from n-butyl to isopropyl, isobutyl, t-butyl, and n-hexyl substituents,R, on 2. Especially, the reaction of -1 to aliphatic ketone such as 2-butanone proceeded in a very poor stereoselection (6% de). To determine the absolute configurationsof B-carbon of the predominant products, the three optically pure diastereomerswere desulfurizedwith Raney-Ni4 to give the corresponding (SI-tertiaryalcohols 5b-d in 100% enantiomeric excess (eel, indicating that all the diastereoisomerswere (SsScl-8-hydroxysulfoxides 3b-d (scheme 1).

5351

These results show that the stereoselectivityfor the asyaetetric addition reaction may be influenced by electronic and steric factors namely, naphthyl-phenylinteraction in 12 the six-memberedcyclic transition state chelated with lithium cation as depicted in 7. Pirkle et al.l3 found that the HPLC separation of the enantiomers of various sulfoxides was achieved by a column

Chelated interaction

,

packed with the chiral 3,5-dinitrobenzoylderivative using

1

_.Li

as the n-acidic site, resulting in the n-basicity of the aromatic portion of methyl I-naphthyl sulfoxide being

p': i

greater than those of phenyl and p-tolyl sulfoxides. The observed (S&I-configuration of the products

x

I

p

coincides with the transition state model z predicted on

U

the assumption that there is a WI charge transfer

sqjARz

'

1

I

&

interaction between the naphthyl group of 1 acted as the

n-n interaction

n-basic site and the phenyl group of 2 as the n-acidic site so that the transition state with aromatic rings

in juxtapositionwould be favorable. Furthermore it gives another support to the transition state 1 that the stereoselectivityfor the addition of 1 to 2-butanone extremely decreased because the n-u interactiondepending upon the orientation of the flat, r-electron faces of two aromatic rings would be not generated between 1 and 2-butanone. The interaction of two aromatic moieties to be face to face as in -7 is also observed for the asynznetric reduction of trifluoromethylphenyl ketone with (S)-chiralGrignard reagent having both phenyl and trifluoromethylgroups to give (Rl-alcohol.14 On the other hand, the drop in stereoselectivityfor the reaction of 1 with the ketones 2e-h having a somewhat bulky alkyl 15 substituentswould be associated with a non- or low coplanarity of the phenyl ring and the carbonyl group of these ketones, that is, a decrease in the coplanarity of zmay

be

reducing the 1-11interaction between -1 and -2 as in -7. A detailed study on the n-n interactionof the two aromatic rings for the addition of sulfinylcarbanionto ketones or imines is now in progress. References and Notes: 1.

For recent reviews see: (a) 6. Solladie, Synthesis,

185 (19811. (bl I&m, hre Appl.

Chem., 60, 1699 (1988). 2. H. Kosugi, H. Konta, and H. Uda, J. c'hem.Sot., them. Cm., 3.

6. Solladie, 6. Demailly, and C. Greek, Tetrahedron Lett.,

4.

N. Kunieda, M. Kinoshita, and J. Nokami, Chem. Lett.,

211 (19851.

26 435 (1985). _' 289 (1977).

5. G. Tsuchihashi, S. Iriuchijima,and K. Maniwa, TetrahedronLett., 6.

S. 6. Pyne and 5. Dikic, J. C&em. SOC., Chm.

Camnu,.,

7. G. Oemailly, C. Greek, and G. Solladie, TetrahedrcmLett., 8.

3389 (19731.

826 (1989). 25, 4113 (1984).

To obtain the optically pure (Sl-l-l-sulfoxide,the crystalline inclusion compound prepared from an aqueous solution of G-cyclodextrin (34.1 g. 30 tmnollwith methyl 1-naphthyl sulfide (5.2 g, 29.8 mnoll was suspended and stirred in a water (100 ml)

5352

containing peracetic acid (40% aqueous solution, 5.7 ml, 30 mnol) at 0% for 65 h under nitrogen.' After the reaction, the 0.1 M aqueous sodium thiosulfate solution was added to decompose the unreacted peracetic acid, and then water was added to dissolve the complex. The aqueous solution was extracted with dichloromethane. The combined dichloromethaneextracts were washed with saturated brine, dried, and evaporated in vacua. The residue was purified by column chromatographyon silica gel (Wakogel C-300) using dichloromethaneas eluent. It gave (S)-(-l-methylI-naphthyl sulfoxide (5.4 g, 28.4 asaol,[aliS

-372.7" in ethanol) with 81% ee in the yield of 95% without sulfone

formation. Recrystallizationof the product from diethylether-pentanemixture yielded the sulfoxide (3.8 g, 20 mmoll which had a purity of 100% ee, as confirmed by 'H NMR (270 MHz) with Eu(hfcI3 or by HPLC analysis on a chiral stationary phase (Daicel Chiralcel 08). For pure (Sl-(-l-l_: mp 55-58°C (lit.lo 58-65°C); IR(KBrI 1049 lS=OI cm-'; 'H NMR(CDCl3, 270 MHz) a 2.84 (s, 3H, CH3), 7.56-7.70 (m, 3H, aromatic), 7.91-7.99 (m, 3H, aromatic), 8.18 (dd, lH, J=7.25, J=1.32 Hz, aromatic); [a];’

-459.8”

(c 0.1, ethanol)".

The detailed results for the asytnaetric oxidation of the other sulfides by this method' will be reported elsewhere. 9.

H. Sakuraba, K. Natori, N. Sato, and Y. Tanaka, The 55th Annual Meeting of The Chemical Society of Japan (Fukuokal,Abstract paper II,

10.

J. Jacobus and K. Mislow, J. Am. them.

SOC.,

p. 704 (1987).

89,

5228 (19671.

11. R. Annunziate, M. Cinqueni, and F. Cozzi, J. C&m.

SOC.

Parkin

I,

1687 (19791.

12. N. Kunieda, J. Nokami, and M. Kinoshita,Cbem. Lett., 369 (1974). 13. W. H. Pirkle, J. M. Finn, J. L. Schreiner, and 8. C. Hamper, J. Am. C&n.

SOC.,

103,

3964 (19811. 14. J. D. Morrison and H. S. Mosher, ' Asyrrmetric

OrganicReactions

Englewood Cliffs, New Jersey, pp 192-193 (1971). 15. G. D. Hedden and W. G. Brown, J. Am. Cbem. SOC., -75, 3744 (1953).

(Received in Japan 4 June 1990)

m Prentice-Hall,Inc.,