Michael Additions of Highly Basic Enolates to <i>ortho</i>-Quinone Methides

A protocol by which ketone or ester enolates and ortho-quinone methides (o-QMs) are generated in situ in a single reaction flask from silylated precursors under the action of anhydrous fluoride is reported. The reaction partners are joined to give a variety of β-(2-hydroxyphenyl)-carbonyl compounds in 32–94% yield in a single laboratory operation. The intermediacy of o-QMs is supported by control experiments utilizing enolate precursors and conventional alkyl halides as competitive alkylating agents and the isolation of 1,5-dicarbonyl products resulting from conjugate additions that do not restore the aromatic system.本研究报道了一种反应方案：在无水氟化物介导下，可从硅基化前驱体在单反应瓶中原位生成酮烯醇负离子、酯烯醇负离子以及邻醌甲基化物（ortho-quinone methides, o-QMs）。将反应底物偶联后，通过单步实验室操作即可得到多种β-(2-羟苯基)-羰基类化合物，产率范围为32%至94%。对照实验验证了邻醌甲基化物的中间体属性：实验采用烯醇负离子前驱体与常规卤代烷作为竞争性烷基化试剂，并分离得到了未恢复芳香体系的共轭加成产物1,5-二羰基化合物。