chromatography, eluting with 3:1 hexane–ether, to give the
cyclopropyl ketone 10b as an oil, Rf 0.53 (2:1 hexane–ether)
22.4Ϫ, 14.0ϩ (Me) and 12.4ϩ (Me); m/z 216.2 (15%, Mϩ), 105.0
(100, PhCO) and 77 (30, Ph).
(Found: Mϩ, 222.1040. C16H14O requires M, 222.1044); νmax
/
cmϪ1 (CHCl ) 1662 (C᎐O), 1599 (Ph) and 1579 (Ph); δ (400
᎐
3
H
(1S,2S,3S)-(2-Butyl-3-methylcyclopropyl)phenylmethanone 47
MHz; CDCl3) 8.02 (2 H, dd, J 1.5 and 8.5, ortho-PhCO), 7.58
(1 H, dt, J, 1.1 and 5.4, para-PhCO), 7.49 (2 H, t, J 5.8, meta-
PhCO), 7.33 (2 H, t, J 7.2, Ph), 7.3–7.2 (3 H, m, Ph), 2.93 (1 H,
By the same general method, silylated hemiacetal21b 45 (112 mg,
0.22 mmol) gave a crude product which was purified by flash
chromatography, eluting with 3:1 hexane–EtOAc, to give the
cyclopropyl ketones 47, 48 and ent-44 (26 mg, 55%, 62:27:11
mixture) as an oil, Rf 0.58 (2:1 hexane–ether); [α]D20 ϩ68.7 (c
0.60 in CHCl3; 76% ee) (Found: Mϩ, 216.1520. C15H20O
requires M, 216.1514); νmax/cmϪ1 (CHCl ) 1661 (C᎐O), 1598
ddd, J 4.1, 5.1 and 8.2, Ph(C᎐O)CH), 2.72 (1 H, ddd, J 4.1, 6.7
᎐
and 8.8, PhCH), 1.95 (1 H, ddd, J 4.2, 5.2 and 9.0) and 1.58
(1 H, ddd, J 4.1, 6.6 and 8.0); δC (100 MHz; CDCl3) 198.5Ϫ
(C᎐O), 140.5Ϫ, 137.8Ϫ, 128.9ϩ, 127.8ϩ, 126.2ϩ, 125.8ϩ, 30.0ϩ,
᎐
29.3ϩ and 19.3Ϫ; m/z 222.1 (45%, Mϩ), 105.0 (100, PhCO) and
᎐
3
(Ph) and 1479 (Ph); δH (400 MHz; CDCl3, major isomer) 7.98
(2 H, dd, J 1.1 and 7.2, ortho-Ph), 7.6–7.4 (3 H, m, remaining
Ph), 2.41 (1 H, dd, J 4.9 and 8.5, Ph(CO)CH), 1.8–1.2 (8 H, m),
1.18 (3 H, d, J 6.0, Me) and 0.81 (3 H, t, J 7.3, Me); δC (100
77 (45, Ph).
(1S,2S)-(2-Butylcyclopropyl)phenylmethanone 10a
Potassium tert-butoxide (180 mg, 1.61 mmol) and the silylated
hemiacetal21b 17a (0.53 mmol) were dissolved in tert-butyl
alcohol (15 cm3) and stirred for 5 h. The reaction mixture was
quenched with water (10 cm3), extracted with ether (3 × 10
cm3), dried (MgSO4) and evaporated under reduced pressure to
give a crude product. Flash chromatography, eluting with 4:1
hexane–EtOAc, to give the cyclopropyl ketone 10a (100 mg,
83%, >95:5 mixture) as an oil, Rf 0.58 (2:1 hexane–ether); [α]D20
ϩ5.3 (c 2.14 in CHCl3; 76% ee) (Found: Mϩ, 202.1356.
C14H18O requires M, 202.1458); νmax/cmϪ1 (CHCl ) 1662 (C᎐O),
MHz; CDCl3) 199.0Ϫ (C᎐O), 139.2Ϫ (ipso-Ph), 132.3ϩ, 128.4ϩ,
᎐
127.9ϩ, 35.9ϩ, 32.1ϩ, 31.9Ϫ, 25.9Ϫ, 23.3ϩ, 22.3Ϫ, 18.3ϩ (Me) and
14.0ϩ (Me); m/z 216.2 (15%, Mϩ), 105.0 (100, PhCO) and 77
(30, Ph).
The minor isomer was identical spectroscopically to the
cyclopropyl ketone 44. The other isomer was identified by the
cyclopropane ring coupling constants: in particular, 2.44 [1 H,
dd, J 4.9 and 9.0, Ph(CO)CH].
᎐
3
(2R,3R)-(2,3-Dipropylcyclopropyl)phenylmethanone 39
1599 (Ph) and 1579 (Ph); δH (400 MHz; CDCl3) 8.01 (2 H, dd,
J 1.4 and 7.2, ortho-Ph), 7.50 (3 H, m, remaining Ph), 2.42 (1 H,
td, J 4.4 and 8.2, Ph(CO)CH), 1.60 (1 H, m), 1.5–1.3 (8 H, m)
and 0.90 (3 H, t, J 7.2, Me); δC (100 MHz; CDCl3) 200.1Ϫ
A stock solution of LDA was prepared by the dropwise addi-
tion of n-butyllithium (1.2 cm3 of a 1.7 mol dmϪ3 solution in
hexanes) to a stirred solution of diisopropylamine (202 mg, 2.0
mmol) in dry THF (8.6 cm3) at 0 ЊC. LDA (5.4 cm3 of a 0.5 mol
dmϪ3 solution in THF) was added dropwise to a stirred solution
of (2S,3R)-1-diphenylphosphinoyl-2-propylhexan-3-yl benzo-
ate 22 (603 mg, 1.34 mmol) and chlorotrimethylsilane (0.63 cm3,
5.0 mmol) gave a crude product. By the general method
described above, potassium tert-butoxide (450 mg, 4.0 mmol)
gave a crude product, which was purified by flash chromato-
graphy, eluting with 5:1 hexane–ether to give the cyclopropyl
ketone 39 (225 mg, 69%) as an oil, Rf 0.65 (3:1 hexane–ether);
[α]D20 Ϫ37.6 (c 1.89 in CHCl3; 84% ee) (Found: Mϩ, 230.1671.
C16H22O requires M, 230.1671); νmax/cmϪ1 (CHCl ) 1662 (C᎐O);
(C᎐O), 138.1Ϫ (ipso-Ph), 128.4ϩ, 127.9ϩ, 126.2ϩ, 33.1Ϫ, 31.3Ϫ,
᎐
27.2ϩ, 25.1ϩ, 20.4Ϫ, 18.9Ϫ and 13.9ϩ (Me); m/z 202.1 (45%, Mϩ),
105.0 (100, PhCO) and 77 (45, Ph).
(1S,2S)-(2-Phenylcyclopropyl)phenylmethanone 10b
By the same general method, silylated hemiacetal21b 17b (60 mg,
0.12 mmol) gave a crude product which was purified by flash
chromatography, eluting with 1:1 hexane–ether to give the
cyclopropyl ketone15,27 10b (16 mg, 62%, >95:5 mixture) as an
oil. Standing in CDCl3 for 3 weeks to give the cyclopropyl
ketone 10b (16 mg, 62%, 67:33 mixture) as an oil (Found: Mϩ,
222.1040. C16H14O requires M, 222.1044); Rf 0.61 (1:1 hexane–
ether); [α]D20 ϩ37.8 (c 0.12 in CHCl3; 86% ee); νmax/cmϪ1
᎐
3
δH (400 MHz; CDCl3) 7.97 (2 H, br d, J 7.1, ortho-Ph), 7.51
(1 H, tt, J 1.2 and 6.4, para-Ph), 7.41 (2 H, br t, J 6.5, meta-Ph),
2.47 (1 H, dd, J 4.9 and 8.3, Ph(CO)CH), 1.9–1.5 (10 H, m),
0.92 (3 H, t, J 7.1, Me) and 0.83 (3 H, t, J 7.2, Me); δC (100
(CHCl ) 1662 (C᎐O), 1599 (Ph) and 1579 (Ph); δ (400 MHz;
᎐
3
H
CDCl3) 7.98 (2 H, dd, J 1.5 and 8.5, ortho-Phmajor), 7.90 (2 H,
dd, J 0.9 and 8.6, ortho-Phminor), 7.6–7.1 (8 H, m, remaining Ph),
3.09 (1 H, ddd, J 5.7, 7.3 and 9.1, Ph(CO)CH minor), 2.90 (1 H,
ddd, J 4.0, 5.2 and 8.1, Ph(CO)CHmajor), 2.70 (1 H, ddd, J 4.1,
6.6 and 8.9, PhCH major ϩ minor), 2.13 (1 H, ddd, J 5.2, 5.8 and 7.0,
minor), 1.93 (1H, ddd, J 4.1, 5.1 and 9.2, major), 1.55 (1 H,
ddd, J 4.1, 6.6 and 8.0, major), 1.46 (1 H, ddd, J 4.8, 7.6 and
8.5, minor); m/z 222.1 (30%, Mϩ), 105.0 (100, PhCO) and 77
(55, Ph). The trans isomer was spectroscopically identical to
that obtained previously.
MHz; CDCl3) 198.9Ϫ (C᎐O), 139.2Ϫ (ipso-Ph), 132.3ϩ, 128.4ϩ,
᎐
127.9ϩ (Ph), 35.6Ϫ, 34.4ϩ, 31.7ϩ, 28.8ϩ, 28.5Ϫ, 22.9Ϫ, 22.6Ϫ,
14.0ϩ (Me) and 13.9ϩ (Me); m/z 230.2 (20%, Mϩ), 187.1 (100,
Mϩ Ϫ Pr) and 105.0 (90, PhCO).
(1R,2R)-[2-(tert-Butyldiphenylsilyloxy)methylcyclopropyl]-
phenylmethanone 36
By the general method described above, (2R)-1-tert-butyl-
diphenylsilyloxy-4-diphenylphosphinoyl butan-2-yl benzoate
29 (776 mg, 1.23 mmol), LDA (5.0 cm3 of a 0.5 mol
dmϪ3 solution in THF, 2.5 mmol), chlorotrimethylsilane (0.62
cm3, 4.9 mmol) and potassium tert-butoxide (413 mg, 3.70
mmol) gave a crude product, which was purified by flash
chromatography, eluting with 4:1 hexane–ether to give the
cyclopropyl ketone 36 (190 mg, 38%) as an oil, Rf 0.53
(2:1 hexane–ether); [α]D20 Ϫ8.4 (c 1.01 in CHCl3; 43% ee)
(Found: Mϩ Ϫ tBu, 357.1311. C27H30O2Si requires Mϩ Ϫ tBu,
(1S,2S,3R)-(2-Butyl-3-methylcyclopropyl)phenylmethanone 44
By the same general method, silylated hemiacetal21b 42 (273 mg,
0.54 mmol) gave a crude product which was purified by flash
chromatography, eluting with 3:1 hexane–EtOAc, to give the
cyclopropyl ketone 44 (97 mg, 84%, 96:4 mixture) as an oil, Rf
0.58 (2:1 hexane–ether); [α]D20 Ϫ0.57 (c 0.96 in CHCl3; 76% ee)
(Found: Mϩ, 216.1520. C15H20O requires M, 216.1514); νmax
/
357.1311); νmax/cmϪ1 (CHCl ) 1666 (C᎐O); δ (400 MHz;
᎐
3
H
cmϪ1 (CHCl ) 1655 (C᎐O), 1598 (Ph) and 1579 (Ph); δ (400
CDCl3) 8.02 (2 H, dd, J 1.0 and 6.3, ortho-Bz), 7.7 (4 H, m),
᎐
3
H
2
MHz; CDCl3) 7.98 (2 H, dd, J 2.0 and 8.1, ortho-Ph), 7.6–7.4
(3 H, m, remaining Ph), 2.11 (1 H, t, J 4.3, Ph(CO)CH), 1.82
(1 H, dqd, J 3.1, 4.3 and 10.0), 1.76 (1 H, dtd, J 4.4, 7.1 and
8.7), 1.6–1.3 (6 H, m), 1.22 (3 H, d, J 6.2, Me) and 0.91 (3 H, t,
7.6–7.35 (10 H, m), 3.92 (1 H, dd, J 4.6 and JHH 10.9,
2
CHAHBOSi), 3.65 (1 H, dd, J 6.1 and JHH 10.9, CHAHBOSi),
2.68 (1 H, td, J 4.4 and 8.0, Ph(CO)CH), 1.86 (1 H, m), 1.51
t
(1 H, m), 1.30 (1 H, m) and 1.09 (9 H, Bu); δC (100 MHz;
J 7.1, Me); δC (100 MHz; CDCl3) 200.0Ϫ (C᎐O), 138.2Ϫ (ipso-
CDCl3) 199.7Ϫ (C᎐O), 138.1Ϫ (ipso-Ph), 135.6ϩ, 135.5ϩ,
᎐
᎐
Ph), 132.4ϩ, 128.4ϩ, 127.8ϩ, 33.5ϩ, 32.4ϩ, 31.7Ϫ, 27.1Ϫ, 26.0ϩ,
134.8Ϫ (ipso-Ph), 134–125 (m), 64.9Ϫ (CH2OSi), 27.8ϩ, 26.9ϩ
J. Chem. Soc., Perkin Trans. 1, 1999, 3425–3433
3431