2-Arylchromans were readily prepared from the hetero-Diels−Alder reactions of styrenes with the ortho-quinonemethides (o-QMs) which, in turn, were generated by treating the MOM-protected benzylacetate derivatives with p-TsOH immobilized on silica (PTS-Si) in toluene under mild conditions (0 °C to rt). The corresponding chromans were obtained in moderate to excellent yields (42−97%) and in moderate
methides (o-QMs) generated from the corresponding benzyl acetate precursors chemoselectively underwent the formal [4 + 2]-cycloadditions with the olefin of styrene, stilbene, or cinnamate derivatives by using different transition metalsalts or Brønsted acids. Such selectivity was obtained when these olefins either separately acted as the dienophiles or were simultaneously present on the same dienophiles.
通过使用不同的过渡金属盐或布朗斯台德酸,由相应的乙酸苄酯前体产生的邻醌甲基化物 ( o -QMs) 与苯乙烯、芪或肉桂酸酯衍生物的烯烃进行化学选择性的形式 [4 + 2]-环加成反应。当这些烯烃分别作为亲双烯体或同时存在于相同的亲双烯体上时,获得了这种选择性。在二苯乙烯烯烃和乙炔之间也实现了完全选择性,为随后的闭环复分解 (RCM) 提供关键的色满中间体,得到相应的四环 5 H-二氢萘并[1,2- c ]色烯。
Facile synthesis of diarylmethanes via quinone methides
A novel acid-mediated generation of quinone methides followed by nucleophilic addition of electron-rich aromatic compounds to furnish diarylmethanes has been developed. A wide range of electron-rich aromatic compounds including some heterocycles can be employed for this reaction to provide the corresponding diarylmethanes in good yields and regioselectivities. (C) 2012 Elsevier Ltd. All rights reserved.