摘要:
1,2-Addition of N-Boc-protected alpha-amino carbanions to cyclobutenediones followed by methylation of the resulting alkoxides generated 4-(1-N-Boc-aminoalkyl)-4-methoxy-3-cyclobutenones. Removal of the Boc protecting group and thermal ring expansion gave dihydro-2-pyridinones in good yields. Treatment of the dihydro-2-pyridinones with NBS/pyridine led to the formation of the corresponding 2-pyridinones. This methodology proved general with regard to both the cyclobutenediones and alpha-amino carbanions.