Kinetic and thermodynamic control in the lithiation of 2,6-dimethylchromone, and selective lithiations in 2-(x-furyl)chromones and in furanochromones related to khellin
作者:Anna M. B. S. R. C. S. Costa、Francis M. Dean、Michael A. Jones、Dennis A. Smith
DOI:10.1039/p19860001707
日期:——
The addition of 2,6-dimethylchromone to lithium di-isopropylamide (LDA) allows formation, under thermodynamic control, of the 2-methylene carbanion (3), but this seems to react at the carbonyl oxygen atom with carbon dioxide so no carboxylic acid can be isolated. With ethyl chloroformate (but not diethyl carbonate) this carbanion does afford the expected ethyl chromon-2-ylacetate (1d). The chromonylacetic
在二异丙基氨基锂(LDA)中添加2,6-二甲基色酮允许在热力学控制下形成2-亚甲基碳负离子(3),但这似乎在羰基氧原子上与二氧化碳反应,因此没有羧酸可以隔离。使用氯甲酸乙酯(而不是碳酸二乙酯)时,该碳负离子确实提供了预期的色散-2-基乙酸乙酯(1d)。如果起始色酮如在(4a)中那样在位置5处具有游离羟基,则也可以获得苯甲酰基乙酸。