Table 3.
Scope and limitations.
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|
| |||||
| Entry | Ester | Product | % Yielda | ||
|
| |||||
| 1 |
|
3 |
|
4 | 28 |
| 2 |
|
5 |
|
6 | <23 (21) |
| 3 |
|
7 | 6 | <24 (19) | |
| 4 |
|
8 | 6 | <26 (20) | |
| 5 |
|
9 |
|
10 | <22 (20) |
| 6 |
|
11 |
|
12 | <31 (28) |
| 7 |
|
13 |
|
14 | n.d.b |
| 8 |
|
15 |
|
16 | 34 |
| 9 |
|
17 |
|
18 | 31c |
aIsolated yields using preparative GPC separation of the crude materials. Compound 6 in entries 3 and 4 contained an impurity of non-negligible amount, despite of repeated purification by GPC. Compound 6 in entry 2, 10 in entry 5 and 12 in entry 6 contained a small amount of impurities (see 13C NMR spectra of compounds 6, 10 and 12 in Supporting Information File 1). Values in parentheses in entries 2–6 are estimated yields, calculated from the ratio of isolated compounds and impurities given in the 1H NMR spectra, because the impurities seem to be the corresponding trialkyl propane-1,2,3-carboxylates (vide infra). bn.d. = no detection. cIsolated yield after silica-gel column chromatography.