COMMUNICATIONS
furnish a pale yellow solution. After the mixture was recooled to 788C,
HMPA (287 mL, 1.65 mmol) and 2-cyclohexen-1-one (96 mL, 1 mmol) were
added. The solution was stirred at 788C for 1 h and poured into water.
After extraction with diethyl ether, the organic extracts were dried over
Na2SO4. Evaporation of solvents and purification of the residue by column
chromatography on silica gel (ethyl acetate/hexane (1/4) as eluant) gave 4
as a white solid (529 mg, 0.93 mmol; 93% yield): 1H NMR (300 MHz,
CDCl3, 258C, TMS): d 7.16 ± 7.77 (m, 20H; Ph), 3.72 (d, 3J(H,H) 2.4 Hz,
1H for a diastereomer; CH(SPh)(SnPh3)), 3.67 (d, 3J(H,H) 1.8 Hz, 1H for
a diastereomer; CH(SPh)(SnPh3)), 1.43 ± 2.50 (m, 9H; COCH2, CH2, and
CH).
comment. The trans-conjugate adducts 6 and 8 afforded
cleavage products 7 and 9, respectively, with high Z selectivity
(Table 1, entries 4 and 7). Since the diastereomeric ratio of the
newly created C C bond in the conjugate adducts 6 and 8 is
about 1:1, the conformations of intermediate carbanions
should be responsible for the stereochemisty of the cleavage
process. The conformer [C] (Scheme 2, n 1, 2) is preferred
over [B] (n 1, 2) due to the steric repulsion between the PhS
and CH3 groups. Such a steric effect is also predominant in the
amphiphilic cleavage of cis-conjugate adduct 10, giving the E
isomer 11 (Table 1, entry 8) by way of the preferred con-
former [D] rather than [E] (Scheme 2).
A solution of 2,6-diphenylphenol (406 mg, 1.65 mmol) in toluene (4.5 mL)
was carefully degassed, and Me3Al (1.0m solution in hexane, 0.55 mL,
0.55 mmol) was added at room temperature under argon. Methane gas
evolved immediately. The resulting yellow solution was stirred for 30 min
and used without purification. After the addition of 4 (285 mg, 0.5 mmol) in
toluene (0.5 mL) and diethyl ether (5 mL) at 788C, the solution was
allowed to warm to 208C, and MeLi (1.0m solution in diethyl ether,
1.5 mL, 1.5 mmol) was added dropwise. The solution was stirred at 208C
for 20 min and then poured into 1n HCl. The mixture was extracted with
diethyl ether, and the organic extracts were dried over Na2SO4. Evapo-
ration of solvents and purification of the residue by column chromatog-
raphy on silica gel (dichloromethane/hexane (1/3) to ethyl acetate/hexane
(1/9) as eluant) gave 5 as a colorless oil (106 mg, 0.479 mmol; 96% yield).
The Z:E ratio of 5 was determined to be 1.3:1 by 1H NMR spectroscopy: Z
isomer: 1H NMR (300 MHz, CDCl3, 258C, TMS): d 7.17 ± 7.42 (m, 5H;
(ATPH)
H
H
(ATPH)
H
H
O
O
H
SPh
H
H
H
PhS
(CH2)n
H
H
(CH2)n
H
H
[C]
[B]
(n = 1, 2)
(ATPH)
E Isomer
H
Z Isomer
3
3
Ph), 6.25 (dt, J(H,H) 9.4, 1.3 Hz, 1H; C CHSPh), 5.78 (dt, J(H,H)
9.4, 7.2 Hz, 1H; CH C), 2.49 (t, 3J(H,H) 7.3 Hz, 2H; COCH2), 2.27 (dq,
3J(H,H) 7.3, 1.3 Hz, 2H; CH2C C), 2.15 (s, 3H; COCH3), 1.74 (quint,
3J(H,H) 7.3 Hz, 2H; CH2); E isomer: 1H NMR (300 MHz, CDCl3, 258C,
TMS): d 7.17 ± 7.42 (m, 5H; Ph), 6.17 (dt, 3J(H,H) 15.0, 1.3 Hz, 1H; C
H
(ATPH)
O
H
O
H
H
H
H
H
SPh
H
H
PhS
CHSPh), 5.91 (dt, 3J(H,H) 9.4, 15.0 Hz, 1H; CH C), 2.47 (t, 3J(H,H)
H
H
[D]
[E]
3
7.3 Hz, 2H; COCH2), 2.18 (dq, J(H,H) 7.3, 1.3 Hz, 2H; CH2C C), 2.15
3
(s, 3H; COCH3), 1.72 (quint, J(H,H) 7.3 Hz, 2H; CH2).
E Isomer
Z Isomer
Received: June 9, 1999 [Z13540]
Scheme 2. The stereochemical outcome of the amphiphilic cleavage of
ketones 6, 8, and 10 with ATPH/MeLi, leading to ketones 7, 9, and 11,
respectively.
[1] Reviews: a) Comprehensive Organic Synthesis, Vol 6 (Eds.: B. M. Trost,
I. Fleming), Pergamon, Oxford, 1991, p. 1041; b) C. A. Grob, P. W.
Schiess, Angew. Chem. 1967, 79, 1; Angew. Chem. Int. Ed. Engl. 1967, 6,
1.
[2] For recent examples of cleavage of C C bonds within a ring, see a) J.
Grimshaw, R. J. Haslett, J. Chem. Soc. Chem. Commun. 1974, 174;
b) M. Takayanagi, N. Umamori, K. Tanino, I. Kuwajima, J. Am. Chem.
Soc. 1993, 115, 12635; c) H. Harayama, T. Kuroki, M. Kimura, S.
Tanaka, Y. Tamaru, Angew. Chem. 1997, 109, 2449; Angew. Chem. Int.
Ed. Engl. 1997, 36, 2352.
The new amphiphilic cleavage of g-stannyl enones descri-
bed herein serves as a highly efficient and general route to
functionalized ketones from commercially available enones,
and therefore should find considerable utility in selective
organic synthesis. Furthermore, this process has been extend-
ed to the selective Cg Cd bond cleavage of ab-enone 12
(E:Z ꢀ 1:1), giving ab-enone 13 in 80% yield (Scheme 3,
(3E,8E):(3E,8Z):(3Z,8E):(3Z,8Z) 45:30:15:10).
[3] Mass Spectrometry of Organic Ions (Ed.: F. W. McLafferty), Academic
Press, New York, 1963.
[4] A similar type of fragmentation was reported by Hamon et al.: D. P. G.
Hamon, G. F. Taylor, R. N. Young, Synthesis 1975, 428; however, such a
fragmentation has not been developed to a synthetically useful level.
[5] ATPH can be prepared by treating 2,6-diphenylphenol (3 equiv) in
toluene with Me3Al at room temperature for 30 min. For other
synthetic applications, see a) K. Maruoka, H. Imoto, S. Saito, H.
Yamamoto, J. Am. Chem. Soc. 1994, 116, 4131; b) K. Maruoka, I.
Shimada, H. Imoto, H. Yamamoto, Synlett 1994, 519; c) K. Maruoka,
M. Ito, H. Yamamoto, J. Am. Chem. Soc. 1995, 117, 9091; d) S. Saito, H.
Yamamoto, J. Org. Chem. 1996, 61, 2928; e) T. Ooi, Y. Hokke, K.
Maruoka, Angew. Chem. 1997, 109, 1230; Angew. Chem. Int. Ed. Engl.
1997, 36, 1181; f) T. Ooi, Y. Kondo, K. Maruoka, Angew. Chem. 1997,
109, 1231; Angew. Chem. Int. Ed. Engl. 1997, 36, 1183; g) S. Saito, M.
Shiozawa, M. Ito, H. Yamamoto, J. Am. Chem. Soc. 1998, 120, 813; h) S.
Saito, H. Yamamoto, Chem. Eur. J. 1999, 5, 1959, and references
therein.
O
ATPH/MeLi
O
SPh
SPh
PhMe/Et2O
–20 °C
80%
SnPh3
12
13
Scheme 3. Selective Cg Cd bond cleavage of enone 12.
Experimental Section
The conjugate addition/cleavage sequence of cyclohexenone (Table 1,
entry 1): To a solution of LDAÐprepared by treatment of diisopropyl-
amine (231 mL, 1.65 mmol) with BuLi (1.6m solution in hexane, 0.94 mL,
1.5 mmol) in THF at 08C for 30 minÐwas added a solution of phenyl-
sulfanyl(triphenylstannyl)methane (710 mg, 1.5 mmol) in THF at 788C.
The mixture was allowed to warm to 208C, and then stirred for 30 min to
[6] T. Kauffmann, R. Kriegesmann, A. Hamsen, Chem. Ber. 1982, 115,
1818.
416
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