was washed on the sinter with a little light petroleum. After
removal of the solvent from the filtrate, the residue was purified
by column chromatography (light petroleum–diethyl ether 95:5
to 5:1 gradient elution) to give the adduct 5aa (0.51 g, 88%) as a
clear oil.
Benzene functioned equally well as the solvent and, when
DLP was used as initiator, all reductive alkylation reactions
were carried out at ca. 80 ЊC under gentle reflux in this solvent.
The characteristics of the racemic adducts 5, 6, 8, and 9 are
given below.
4.72 (1 H, dd, J 11.0 and 2.2, OCH); δC 20.9, 24.9, 25.9, 31.0,
34.6, 51.6, 79.9, 171.1, 173.7; νmax (film) 2966, 1739, 1435, 1371,
1242, 1167, 1021, 960, 878, 707 (Found: C, 61.1; H, 9.2.
C11H20O4 requires C, 61.09; H, 9.32%).
Dimethyl (2-tert-butyldimethylsiloxypropyl)malonate 5ca. Oil;
δH 0.01 (3 H, s, SiMe), 0.04 (3 H, s, SiMe), 0.87 (9 H, s, But),
1.15 (3 H, d, J 6.1, MeCH), 1.93 (1 H, ddd, J 13.8, 8.9 and 4.8,
CHAHB), 2.07 (1 H, ddd, J 13.8, 9.6 and 3.7, CHAHB), 3.62
(1 H, dd, J 9.6 and 4.8, CH), 3.73 (3 H, s, OMeA), 3.74 (3 H, s,
OMeB), 3.83 (1 H, m, OCH); δC Ϫ5.1, Ϫ4.3, 19.0, 23.9, 25.8,
38.3, 48.2, 52.4, 52.6, 66.0, 170.0, 170.3; νmax (film) 2956, 2858,
1739, 1438, 1342, 1253, 1152, 1001, 837, 777 (Found: C, 56.6;
H, 7.4. C13H22O6Si requires C, 56.35; H, 7.43%).
Dimethyl (2-acetoxypropyl)malonate 5aa. Oil; δH 1.24 (3 H, d,
J 6.2, Me), 2.00 (3 H, s, Ac), 2.35 (2 H, m, CH2), 3.46 (1 H, dd,
J 8.6 and 6.1, CH), 3.72(7) (3 H, s, OMeA), 3.73(2) (3 H, s,
OMeB), 4.89 (1 H, m, OCH); δC 20.1, 21.1, 34.7, 48.4, 52.7(5),
52.7(7), 68.7, 169.3, 169.5, 170.4; νmax (film) 2956, 2361, 1738,
1438, 1375, 1244, 1158, 1066, 953 (Found: C, 51.8; H, 6.8.
C10H16O6 requires C, 51.72; H, 6.94%).
Dimethyl 3-oxaheptylmalonate 5da. Oil; δH 0.89 (3 H, t, J 7.3,
Me), 1.43 (2 H, m, CH2), 1.50 (2 H, m, CH2), 2.16 (2 H, m,
CH2), 3.36 (2 H, t, J 6.5, CH2O), 3.43 (2 H, t, J 6.0, CH2O), 3.56
(1 H, t, J 7.3, CH), 3.72 (6 H, s, 2 OMe); δC 13.9, 19.2, 29.0,
31.7, 48.8, 52.5, 53.9, 67.7, 70.7, 169.8; νmax (film) 2959, 2870,
1736, 1437, 1160, 1116, 1017, 707 (Found: C, 56.7; H, 8.7.
C11H20O5 requires C, 56.88; H, 8.68%).
Methyl 4-acetoxypentanoate 5ab. Oil; δH 1.21 (3 H, d, J 6.3,
Me), 1.87 [2 H, m, CH2C(O)], 2.00 (3 H, s, Ac), 2.34 (2 H, m,
CH2CO), 3.65 (3 H, s, OMe), 4.89 (1 H, m, OCH); δC 19.8, 21.2,
30.1, 30.8, 51.6, 69.9, 170.6, 173.4; νmax (film) 2980, 2953, 1738,
1439, 1375, 1245, 1077, 964, 707 (Found: C, 55.4; H, 8.0.
C8H14O4 requires C, 55.16; H, 8.10%).
Dimethyl 2-methylheptylmalonate 5ea. Oil; δH 0.87 (3 H, t,
J 7.0, Me), 0.88 (3 H, d, J 6.5, MeCH), 1.0–1.5 (9 H, 4 CH2 and
1 CH), 1.67 (1 H, ddd, J 14.5, 7.9 and 6.6, CH CHAHB), 1.96
(1 H, ddd, J 14.5, 8.6 and 5.5, CH CHAHB), 3.47 [1 H, dd, J 8.6
and 6.6, CH(CO2Me)2], 3.72(5) (3 H, s, OMe), 3.72(9) (3 H, s,
OMe); δC 14.1, 19.2, 22.6, 26.3, 30.8, 32.0. 35.9, 36.6, 49.8, 52.4
52.5, 170.1, 170.2; νmax (film) 2956, 2857, 1739, 1437, 1331,
1247, 1200, 1154, 1015, 976 (Found: C, 63.8; H, 10.0. C13H24O4
requires C, 63.91; H, 9.90%).
Diethyl (2-acetoxypropyl)methylmalonate 5ac. Oil; δH 1.21–
1.28 (9 H, m, 3 Me), 1.40 (3 H, s, Me), 1.95 (3 H, s, Ac), 2.10
(1 H, dd, J 15.0 and 3.0, CH2A), 2.33 (1 H, dd, J 15.0 and 10.5,
B
CH2 ), 4.15 (4 H, m, OCH2), 5.03 (1 H, m, OCH); δC 14.0, 19.4,
21.0, 40.7, 52.0, 61.1, 61.4, 67.4, 170.3, 171.8, 172.1); νmax (film)
2984, 2940, 1736, 1454, 1376, 1296, 1242, 1116, 1020, 951, 862
(Found: C, 57.2; H, 8.2. C13H22O6 requires C, 56.92; H, 8.08%).
Dimethyl 3-acetoxy-2-methylpropylmalonate 5fa. Oil; δH 0.95
(3 H, d, J 6.4, Me), 1.79 (2 H, m, CH2), 2.04 (1 H, m, CH), 2.05
(3 H, s, Ac), 3.50 [1 H, dd, J 8.4 and 6.8, CHC(O)], 3.73 ( 6H, s,
2 MeO), 3.91 (2 H, ddd, J 13.7, 11.0 and 5.5, OCH2); δC 16.5,
20.8, 30.6, 32.6, 49.4, 52.6 (2 C), 68.6, 169.6, 169.8, 171.0; νmax
(film) 2959, 1738, 1439, 1369, 1242, 1157, 1038, 911 (Found: C,
53.7; H, 7.4. C11H18O6 requires C, 53.65; H, 7.37%).
Admantyl 4-acetoxypentanoate 5ad. Oil; δH 1.21 (3 H, d,
J 6.3, Me), 1.65 ( 6 H, br s, 3 CH2 of Ad), 1.82 (2 H, m,
CH2CH2CH), 2.01 (3 H, s, Ac), 2.08 (6 H, br s, 3 CH2 of Ad),
2.13 (3 H, br s, 3 CH of Ad), 2.24 (2 H, m, OCCH2), 4.90 (1 H,
m, CHOAc); δC 19.9, 21.3, 30.8, 31.0, 31.7, 36.2, 41.3, 70.1,
80.5, 170.6, 172.0; νmax (film) 2914, 2856, 1735, 1452, 1373,
1243, 1181, 1056, 966, 869 (Found: C, 69.6; H, 9.0. C17H26O4
requires C, 69.36; H, 8.90%).
(2-Acetoxypropyl)triphenylsilane 6. Mp 61–62 ЊC; δH 1.21 (3
H, d, J 6.1, MeCH), 1.68 (3 H, s, Ac), 1.73 (1 H, dd, J 14.9 and
6.4, SiCHA), 1.98 (1 H, dd, J 14.9 and 8.0, SiCHB), 5.16 (1 H, m,
CHOAc), 7.31–7.62 (15 H, m, 3 Ph); δC 20.9, 21.9, 23.5, 69.2,
127.9, 129.5, 134.6, 135.6, 170.3; νmax (mull) 1720, 1247, 1109,
948 (Found: C, 76.6; H, 6.6. C23H24O2Si requires C, 76.62; H,
6.71%).
1-(4-Acetoxy-1-oxopentyl)admantane 5ae. Oil; δH 1.21 (3 H,
d, J 6.3, Me), 1.69–1.90 (17 H, complex Ad and CH2), 2.02
(3 H, s, Ac), 2.47 (2 H, m, OCCH2), 4.87 (1 H, m, CHOAc);
δC 20.1, 21.4, 27.9, 29.7, 31.9, 36.5, 38.3, 46.3, 70.5, 170.7, 214.6;
νmax (film) 2908, 2852, 1736, 1698, 1451, 1373, 1244, 1013, 952,
707 (Found: C, 73.5; H, 9.3. C17H26O3 requires C, 73.35; H,
9.41%).
5-[2,2-Bis(methoxycarbonyl)ethyl]tetrahydrofuran-2-one
8.
Oil; yield 72%; δH 1.90 (1 H, m, CHCHAHBCH), 2.15 (1 H, ddd,
J 15.1, 9.7 and 5.3, CHCHAHBCH), 2.23 (2 H, m, 4-H), 2.53
(2 H, m, 3-H), 3.66 [1 H, dd, J 9.4 and 5.3, CHC(O)], 3.73 (3 H,
s, OMeA), 3.75 (3 H, s, OMeB), 4.52 (1 H, m, OCH); δC 27.9,
28.4, 34.7, 48.2, 52.8, 77.8, 169.1, 173.3; νmax (film) 2957, 1735,
1740, 1438, 1180, 1043, 926, 652 (Found: C, 52.3; H, 6.2.
C10H14O6 requires C, 52.17; H, 6.13%).
3-Acetoxybutyl phenyl sulfone 5af. Oil; δH 1.21 (3 H, d, J 6.0,
Me), 1.98 (2 H, m, CH2), 2.00 (3 H, s, Ac), 3.13 (2 H, m,
CH2SO2), 4.92 (1 H, m, CHOAc), 7.59 (2 H, m, Ph), 7.91 (1 H,
m, Ph), 7.93 (2 H, m, Ph); δC 19.9, 21.2, 28.8, 52.8, 68.8, 128.1,
129.4, 133.9, 138.9, 170.2; νmax (film) 1736, 1447, 1374, 1307,
1243, 1148, 1088 (Found: C, 56.2; H, 6.5; S, 12.3. C12H16O4S
requires C, 56.23; H, 6.29; S, 12.51%).
5-Triphenylsilylmethyltetrahydrofuran-2-one 9. Mp 96–98 ЊC;
δH 1.65 (1 H, m, 4-HA), 1.80 (1 H, dd, J 14.4 and 9.5, SiCHA),
1.97 (1 H, m, 3-HA), 2.23 (1 H, dd, J 14.4 and 5.0, SiCHB), 2.40
(2 H, m, 4-HB and 3-HB ), 4.72 (1 H, m, OCH), 7.3–7.6 (15 H,
m, 3 Ph); δC 21.5, 29.5, 30.8, 79.5, 128.1, 129.9, 133.7, 135.6,
176.8; νmax (mull) 1736, 1105, 968, 725 (Found: C, 77.2; H, 6.3.
C23H22O2Si requires C, 77.06; H, 6.19%).
Dimethyl 2-acetoxy-3,3-dimethylbutylmalonate 5ba. Oil; δH
0.90 ( 9 H, s, But), 1.98 (1 H, ddd, J 14.4, 11.1 and 4.8, CHAHB),
2.05 (3 H, s, Ac), 2.28 (1 H, ddd, J 14.4, 9.9 and 2.0, CHAHB),
3.33 [1 H, dd, J 9.9 and 4.8, CHC(O)], 3.72 (3 H, s, OMeA), 3.74
(3 H, s, OMeB), 4.73 (1 H, dd, J 11.1 and 2.0, AcOCH); δC 20.8,
25.7, 29.2, 34.7, 48.7, 52.7, 78.2, 169.8, 171.0; νmax (film) 2961,
1738, 1437, 1372, 1243, 1155, 1022, 958, 892 (Found: C, 56.9;
H, 8.0. C13H22O6 requires C, 56.92; H, 8.08%).
Enantioselective reactions
Enantioselective reductive alkylation reactions were carried out
in refluxing benzene, using the general method described above,
with DLP as the initiator (10 mol% based on alkene) and one of
the homochiral thiols 15–18 as catalyst (10 mol%). The optical
Methyl 4-acetoxy-5,5-dimethylhexanoate 5bb. Oil; δH 0.91
(9 H, s, But), 1.75 (1 H, m, CHAHB), 1.95 (1 H, m, CHAHB), 2.06
(3 H, s, Ac), 2.28 (2 H, t, J 7.9, CH2CO), 3.68 (3 H, s, OMe),
2066
J. Chem. Soc., Perkin Trans. 1, 1999, 2061–2068