Table 1.
Imine | R′ | S stereocenterb | Rc | yield | drd | ΔΔE‡e |
---|---|---|---|---|---|---|
2 | t-butyl | S | BDA | 92% | > 95:5 | +1.8 |
3 | t-butyl | S | cyclohexyl | 81% | 61:39 | +0.9 |
4 | 4-methylphenyl | S | BDA | 80% | 67:33 | +1.1 |
5 | t-butyl | R | BDA | 88% | 79:21 | -1.2 |
ent-2f | t-butyl | R | ADB | 94% | > 95:5 | -1.8 |
ent-5f | t-butyl | S | ADB | 89% | 79:21 | +1.2 |
Experimental data from Ref. [5].
Configuration of sulfinyl sulfur atom.
BDA denotes the protected diol as shown in Figure 1, as derived from D-mannitol; ADB denotes the mirror image of BDA, as derived from ascorbic acid.
Determined by 1H NMR (crude reaction mixture).
ΔΔE‡ estimated as E(TSRe) − E(TSSi), based on ZPE-corrected B3LYP/6-311+G**(THF) energies. Positive value indicates Si TS favored, negative value indicates Re TS favored.
Enantiomers of imines 2 and 5, respectively. ΔΔE‡ values are given by symmetry.