Validation of the substituent effect in the reaction of 1a with a series of dienylcarbamatesa.
| |||||
|---|---|---|---|---|---|
| Entry | X | Product | Yieldb (%) | endo/exoc | eec (%) |
| 1 | H (2b) | 3ab (Cbz) | 86 | 98 : 2 | 91 |
| 2 | Br (7b) | 11ab (CbzBr) | 98 | 98 : 2 | 95 |
| 3 | NO2 (8b) | 12ab (CbzNO2) | 98 | 99 : 1 | 98 |
| 4 | Me (9b) | 13ab (CbzMe) | 85 | 98 : 2 | 90 |
| 5 | MeO (10b) | 14ab (CbzMeO) | 95 | 98 : 2 | 90 |
a
General conditions: 1a (0.1 mmol), dienylcarbamate (0.3 mmol), and (S)-6 (0.01 mmol) in toluene (1 mL) with MS 5A (50 mg) at room temperature for 5 days.
b
Isolated yield.
c
Diastereomeric and enantiomeric excess were determined by chiral stationary phase HPLC analysis.