scheme4
![Organocatalytic regio- and enantioselective formal [4 + 2]-annulation of chiral nitrogen-containing dipoles](https://image.oaes.cc/b9b30f0a-ea14-42f0-9762-04cc46829046/5421.scheme.4.jpg)
Scheme 4. Substrate scope of the reaction between benzoxazines 1 and 2-methylene-3-oxoalkanoates 4. A mixture of 1 (0.1 mmol), 4 (0.2 mmol), and C5 (10 mol%) in CH2Cl2 (0.1 mL) was stirred at 35 °C for 96 h. All dr > 20:1, determined by 1H NMR. Products 5 were obtained in isolated yield. The enantiomeric excess (ee) was determined by chiral-HPLC analysis.